Larson Davis FAQ

When do I need to use the Type 2 Adapter for circumaural earphones?

Type 2 Adapter for circumaural earphones

You need the AEC201-2 Type 2 adaptor for circumaural earphones only for KOSS HV/1A type earphones.


The Type-2 adapter is the flat crenellated adapter plate converting the Acoustic Coupler for use with Circumaural Earphones. This adapter is mentioned in ANSI S3.6 (2010) and in ISO 389-5 for use with the KOSS HV/1A earphones.


From ANSI S3.6 (2010) we have the following:


The IEC 60318-1 (2009) no longer mentions the crenellated Type 2 adapter. (IEC 60128-1 and IEC 60318-2 have been merged into IEC 60318-1(2009).) ISO 389-5 for the HF RETSPL in Annex B shows again the crenellated adapter for KOSS HV/1A

How do I combine Model 831 and DNA for RT60 measurements?

There are in principle two ways to use DNA for RT60.  Both options require the DNA option for building acoustics, SWW-DNA-BA, and Model 831 driver, SWW-DNA-831.

  • Making RT60 measurements on the 831 (Requires 831-RT and you must save all time series decays)
  • Making RT60 measurements in DNA, with 831 as acquisition front-end in SLM mode (Requires 831-LOG, 831-OB3, and 831-FST)

Both methods will give you access to the RT60 display / menu, shown below.

This window allows you to:

-       View RT20, RT30, or RT15 data.

-       See the spectrum

-       Delete a decay

-       Translate data for import into DNA for analysis and graphing


Importing data from 831-RT (DNA will recalculate RT15, 20, 30 based on recorded decays)

-       Make and store an RT60 measurement on the Model 831.

-       Start DNA, connect to the 831, (Analyzer, 831, then click the connect icon).

-       In DNA831 analyzer window:

  • Download the file using Analyzer->Download from Analyzer
  • Uncheck the Translate binary .slmdl files to DNA4
  • Select the file and click Download
  • Close the Download files window after the file is downloaded. You could also load a previously stored slmdl file in the next step.
  • Click RT60 Measurement, select RT60 Mode, check Load measurement from a .r .slmdl file, click OK, select file, then click open.

-       You can toggle the RT60 window, on or off using the RT60  menu button

Viewing RT60 data in DNA


-       In the RT60 window, select Options, and put a checkmark in Schroeder Backward Integration and Use Ensemble averaging between positions, then click OK.

-       You can save the data in an RTdat file (RT60 Measurement -> Save as from the main menu) and reload later.

-       Click Export to doc, select if you want to export all decays, click OK, then you can include your measurement info and click OK. The data will be translated to the DNA document window.


NOTE: You can switch the 831 from RT60 mode to SLM mode using the DNA DirectScreen option in the View drop-down menu. It is recommended to disconnect and reconnect the 831.


Measuring RT60 with DNA and the 831

-       Start a new measurement with (RT60 Measurement -> New)

-       Turn above display on using RT60 icon

-       Push Run and use the Accept/Reject buttons until you Stop

-       The Run/Stop acts as position increment just like Start/Stop does on 831.


Translating  the RT60 data to DNA for reporting

There are 2 ways here too:

1)     Via the graph above using the Export to doc button

2)     Or via the RT Measurement -> Translate RT60 menu


The 3 template options are:    RT60 spectrum only

                                                RT60 spectrum with multi-column table (best for 1/3rd octave)

                                                RT60 spectrum with single column table (best for 1/1 octave)

See DNA-BA Architectural Acoustics to further tune the RT results in DNA

How does the RT60 implementation on the Model 831 differ from the 824?

How do I setup Sierra Wireless LS300 for sending SMS with NoiseTutor?

Sierra Wireless LS300 Description

The Sierra Wireless LS300 is a new model wireless gateway designed to replace the Raven product line and support 4G data.

The LS300 is used inside the NoiseTutor system to provide a wireless data connection and SMS messaging.  For data service the factory default settings are typically adequate although for SMS messaging to work, some configuration of the LS300 is necessary. 


Required Items

  • Sierra Wireless LS300
  • SIM card with messaging and a data plan.  Voice is not needed
    • APN name (provided by cellular service provider)
  • CAT5 network cable

Configuring the LS300

The LS300 has a built-in web page called AceManager that is used to configure the device and detailed instructions for accessing and using AceManager are included in the LS300 User Manual.  This document provides an overview of the necessary steps.

1)     Connect a PC (typically the NoiseTutor PC) to the LS300 using a CAT5 cable and power on the LS300

2)     Open a web browser and enter in the address bar and the login screen should appear.  If you don’t see the login screen, reboot the PC and repeat this step.

3)      The default administrator user name is user and the default password is 12345

4)     Most cellular service providers require an Access Point Name, APN, be configured for the system to work properly.  When an APN is needed but not entered, they LS300 will not be able to access the internet.

a.     Acquire the APN name from your cellular service provider

b.    On the top tab, select WAN/Cellular

c.     In the box titled APN enter the APN name from your CSP

d.    Continue to step 5 or select Apply and Reboot if SMS messaging is not being configured

e.     When the APN is correctly set and cellular service is available, the LS300 will be able to acquire an IP address

5)      On the top tabs, select Services then on the vertical tabs select SMS

6)     In the drop down titled SMS Mode select Gateway Only

7)     In the field titled ALEOS Port enter then number 17341

8)     Select Apply and then Reboot

The LS300 is now configured to send SMS messages using UDP port 17341



Configuring NoiseTutor to Send SMS using the LS300

1)     In the NoiseTutor software, select Setup > Messaging > SMS to open the SMS setup dialog

2)      On the dropdown titled Select SMS protocol select Sierra Wireless IP-SMS

3)     In the field titled Modem IP address enter the default IP address of the LS300 which is

4)     In the field titled Modem UDP port enter the number 17341

5)     Use the button Send test SMS… to verify that an SMS message can be sent then click OK

6)     NoiseTutor is now configured to send SMS messages.  Go to Setup > Event Detection > Event to configure an SMS message when an event has occurred.




How do I connect the 426A12 outdoor microphone to a Model 820, 824, or 870 sound level meter?

How do I connect the 426A12 outdoor microphone to a Model 820, 824, or 870 sound level meter?

The 426A12 can output signals that could potentially damage the input circuitry of the 820, 824 or 870 sound level meter.  To correctly interface these SLM’s to the 426A12 use the additional equipment listed in Table 1.  See Figure 1 and Table 2 for additional information on the connections.

Table 1.  Additional Equipment Required for Connection to 426A12



1Connecting additional preamp and ADP006 directly into SLM signal connector may be too tall for NMS box.  Using CBL078 or CBL092 short extension cable makes the connections possible and also allows fit inside NMS box.

2 Cable has default length of 20 feet.  Custom lengths are also available.

3 If 426A12 is directly replacing a PRM2100K or PRM2101K a 426A12-NPT adaptor pipe coupler will be required.


Figure 1. Block diagram of interconnections



Table 2. Control Cables Used


4 An optional adapter cable, S2175.03, is available to connect the CBL197 control cable to a Larson Davis outdoor monitoring system that has a power and ground block system (see Figure 1 for additional information).

Will the 426A12 mount directly to an existing pole that previously had a PRM2100K or PRM2101K mounted to it?

The PRM2100K and PRM2101K both use a 1.5”-11.5 NPT mounting thread, whereas the 426A12 uses an ISO 228-1 G 1.5” mounting thread.  The 426A12-NPT adapter pipe coupler is available to convert the 1.5” NPT to the required ISO 228-1 G 1.5” thread, allowing the mounting of the 426A12 to the original pole.


What 426A12 features are available when used with the Model 820, 824, or 870 SLM?

The following features of the 426A12 are available when used with the Model 820, 824, or 870 SLM:

  • Microphone preamplifier signal conditioning.
  • Selectable weighted filters:  A, C, or Z weight.
  • Selectable microphone polarization: 0 or 200 volts.
  • Selectable gain: 0 or 20 dB.
  • Electrostatic actuator for calibration check.
  • Microphone humidity control using desiccant cartridges with visible indicators through window.


The following features of the 426A12 are not available when used with the Model 820, 824, and 870 SLM’s:

  • Reading the 426A12 internal temperature and humidity sensors (through serial communications).
  • Reading the 426A12 model and serial number electronically (TEDS).

How does the additional in-line preamp affect the performance of the system?

The additional in-line microphone preamplifier (PMR828, PRM902, or PRM900) does slightly change the dynamic range and noise floor relative to the original outdoor system.  Listed below are typical results, comparing the PRM2100K and PRM2101K outdoor microphone preamplifiers to the 426A12 configured with the additional equipment listed in Table 1.

All of the test are performed with a 12 pF equivalent microphone capacitance at the front end of the outdoor microphone preamplifier.  The ADP006 (47 pF) adapter at the input of the PRM828, PRM902, or PRM900 has negligible effect to the noise floor and frequency response of the system.


How do I connect a Hydrophone with an 831?

Overview:   Connect a Model 831 to an underwater hydrophone. 

Features :  Model 831 Measures underwater noise.

The 831 can connect to a piezoelectric hydrophone -

  1. Replace the microphone with an ADP005 ‘dummy mic’ adapter
  2. Connect the hydrophone to the BNC connector end of the ADP005
  3. Using the adapter, place the hydrophone in a pistonphone adapter to calibrate
  4. On the Model 831 select TOOLS and create a calibrator entry for the pistonphone.  Set the calibrator level to the appropriate level (see below) and the frequency to 250 Hz.  The level may be different for differing models of pistonphones.  Consult the pistonphone manufacturer’s documentation to determine the correct level.
  5. Calibrate. Although reference pressure levels differ for measurements in air and water, this step will adjust the Model 831 for to account for this difference. 20 μPa is typically used as a reference for air, and 1 μPa for water. The difference is 20x in the linear domain, and 26 dB (26.02 dB to be exact) in the log domain. As an example, 1 Pascal pressure equates to 94 dB re. 20 μPa in air and 120 dB re. 1 μPa in water.

Note: When using the RA0043 hydrophone adaptor with a pistonphone, the volume is changed slightly and therefore a hydrophone calibration adapter correction factor should be applied. The calibration factor can be found on the RA0043 calibration chart or is etched on each adapter.

Note: the K-Factor can also be verified in the field by using the 1/2" sampling port on the side of the adapter.


Example: To calibrate using a standard 114 dB pistonphone such as GRAS 42AA, enter 144.5 dB:

use actual sensitivity from calibration sheet to change reference pressure from 20 μPa in air to 1 μPa for water K-Factor, correction for volume difference when using RA0045 Sensitivity to enter in 831 when calibrating TC4013 hydrophone

What Precautions should I take when using external DC power with my sound level meter?

The Model 831 sound level meter can be powered several different ways including

A)   Internal AA batteries

B)   USB

C)   External 12V DC supply


The Model 831 includes many input power protections to help avoid damaging the instrument.


Input Power Protections


A)   When using internal AA batteries – The Model 831 is protected from reverse polarity and includes a 0.75 ampere fuse in the positive supply

B)   When using USB current limit protection is provided by the USB port supplying power, i.e. PC, hub or PSA029.

C)   When using the 12V DC input – There is a 0.5 ampere fuse in the positive supply and reverse polarity protection




The Model 831 ground or negative supply is available in multiple locations and can be found at:

  • The preamplifier, typically PRM831, and the interconnecting cables
  • The metal nose on the 831 body
  • The USB connector and interconnecting cables
  • The AC/DC output connector
  • The connector for 12V DC input
  • The negative terminal of the internal batteries


Internal to the Model 831 all grounds are electrically connected and there are no fuses or other protection against externally induced ground current.  It is therefore important that all 831 ground points remain at the same voltage.  Failure to keep the ground voltage consistent can result in electrical currents that can permanently damage the Model 831.


A voltage differential can be created by a variety of situations and listed below are a few.

1)    The exterior of the preamplifier, microphone or cable connector comes in contact with an unprotected power supply such as the positive terminal of a battery.

2)    The shield of a USB cable that is connected to the 831 comes in contact with an unprotected external power supply.


How to Protect Against Destructive Short Circuits

A)   Make sure all power connections are covered by an electrically insulating material.  This includes the terminals of any external 12V batteries which should have terminal covers securely installed that cover all conductive portions of the terminal and connector.

B)   Disconnect power when servicing the Model 831 or system components by disconnecting the negative wire from any external batteries

C)   Use a 4 ampere fast blow fuse in both the positive and negative terminals of any external power cables.

D)   When shipping, use the following precautions

a.    Ship systems without the battery installed to prevent possible short circuiting while in transit

b.    Alternatively, disconnect and secure the negative wire during transit

c.    Review and follow instructions provided by the shipper for shipping batteries

d.    Review and follow and instructions specific for the system being shipped

E)   Store cables securely to avoid accidental movement and an inadvertent short circuit




What is the difference between the 831-INT and 831-INT-ET?

1       What is the difference between the 831-INT and 831-INT-ET?

The 831-INT has the following summary features:

  • Battery management and charging controls
  • System operating properly watchdog
  • Four port powered USB hub
  • Power and control signals for 426A12 and PRM2103 outdoor preamplifiers
  • Digital I/O

In addition to the 831-INT features, the 831-INT-ET adds network communications capability to the 831 SLM, by adding the following features:

·         Embedded Single Board Computer (SBC).

·         Single RJ45 Ethernet connector.

·         Additional USB Ports A and B (as part of SBC).  Connect USB Port B to the 831 SLM’s USB port.

·         Ethernet connection enables faster connection speeds, real-time streaming of data, and also remote firmware upgrade.

For more information please refer to the I831.04 831-INT/831-INT-ET Technical Reference Manual.

2       What are the differences between the various revisions?

Differences between the various revisions of the 831-INT/831-INT-ET are listed below in Table 1.  Features not listed in the table are common to all versions.

Table 1.  Differences between various 831-INT/831-INT-ET Revisions

1 The system will power off when the battery voltage falls to the external power shut-off voltage as set in the Model 831 (default=10.8 volts), and will power up when the battery voltage returns to 11.6 - 12.3 volts.

2 The system will power off when the battery voltage falls to the external power shut-off voltage as set in the Model 831 (default=10.8 volts), and will power up when the battery voltage returns to 12.5 volts for at least 2 minutes.

3 The system status LED has enhanced functionality.


3       New features introduced in Revision G

The 831-INT(-ET) has been enhanced to provide improved protection to vulnerable Flash Memory chips along with the addition of other feature.

To take full advantage of the new 831-INT-ET features, use Model 831 firmware V2.2 or later.


Feature Summary:

-       The watchdog for the single board computer in an 831-INT-ET and the 831 are now independent.  If the SBC fails and requires a watchdog reset, the 831 will no longer be rebooted but will remain operational

-       SBC power on time has been shortened

-       The system status LED (Mains Status) has been enhanced to show the following information

  •  LED is remains lit during normal operation.  LED will briefly blink off when the 831 watchdog is reset for the 831-INT or fade up and down with no delay when the 831 and SBC watchdogs have been reset recently for the 831-INT-ET
  • LED will quickly flash when power off is imminent or in progress.  This can be due to low battery, watchdog, or the 831 being shut off
  • LED will be off and flash on every 4 seconds when system is powered off
  • LED will be off and flash on every 8 seconds when system is powered off, there is no mains power, and battery voltage is too low to restart the system.  The battery must be recharged to 12.5V or greater or mains power restored before the system will restart

-        The Battery Charger Status LED has been enhanced and the LED will blink fast when there is a fault, either a thermistor fault or no battery found

-       The threshold for system power on when battery is recharged is now 12.5V for at least 2 minutes

4       What is required to replace an 831-INT rev A in an EPS031 or EPS032 system with a later revision?

The enclosure for 831-INT/831-INT-ET became 1/8” thicker after revision A.  Because of this size difference, the two mounting brackets below must be ordered and replaced when updating from a revision A 831-INT:

  • M831.56 – NMS Rotating Bracket.
  • M831.57 – NMS Stationary Bracket.

Replacing these brackets in an EPS031/EPS032 system involves removing all the equipment from the box to gain access to the back plane of the EPS031/EPS032.  It’s estimated this procedure will take 30 to 60 minutes to perform.

The above procedure is not necessary for newer EPS031/EPS032 systems as they already come with the modified M831.56 and M831.57 brackets installed.

5       Is my 831-INT rev A or 831-INT/831-INT-ET rev B repairable?

If an 831-INT rev A or 831-INT/831-INT-ET rev B cannot be repaired the entire unit will be replaced using later revision product.  If a revision A 831-INT is replaced, the M831.56 and M831.57 brackets will also require replacement if used in the system.  If a revision B 831-INT(-ET) is replaced, then only the M831.56 rotating bracket may need to be replaced. 

6       How do I upgrade firmware in an 831-INT-ET?

        a)   Check 831-INT-ET firmware revision using SLM Utility G3



b)       831-INT-ET firmware version is prior to version 2.2, the upgrade is made by replacing the SDflash chip that is inside the 831-INT-ET.  This can be done in the field and requires about 5 minutes and a Phillips screwdriver

        a. Request a new chip from Larson Davis by contacting customer support

        b. Remove the screw for mounting the 831


        c. Using a Phillips screwdriver, remove the 4 screws from the top of the 831-INT-ET and remove the top cover

d. After removing the top cover, the U-shaped metal piece will lift off over the connectors exposing the circuit board.  Use proper grounding techniques to avoid static discharge to the circuit board or any component on the board.  Static discharge can cause permanent damage.

e.  Locate the chip carrier and slide the lid back (direction of arrow) slightly to release the chip

f.   Remove the old chip and insert the new chip in the lid, push down the lid and slide forward to lock the chip.

g.  Reassemble the system


 c.  831-INT-ET firmware version 2.2 or later then SLM Utility G3 can be used to load new firmware.

How do I connect to a 831-INT-ET with wired Ethernet?

Required equipment:

  • Model 831 running firmware V2.110 or later
  • Model 831-INT-ET Docking station with firmware V2.1 or later
  • Wired Router with at least 2 ports and 2 CAT5 cables

1.     In order to avoid conflict with existing other networks, please ensure the wireless LAN on your PC is DISABLED.

2.     Boot up the router connecting your PC using a CAT5E cable using port 1 of the router. Check with the standard tools to find the IP address. In the display below you will recognize:

a)     Default Gateway:

                        b)    IP Address (of your PC):



    3.    Prepare the 831-INT-ET with 831

a)     Place the 831 in the 831-INT-ET cradle and secure with the screw.

b)    Connect the 831 USB cable to the 831-INT-ET “USB B” port.

c)     Connect the LAN cable from the 831-INT-ET “Ethernet” port to port 2 on the router.

d)    Power up the 831-INT-ET

e)     Wait about 3 minutes to be sure that the 831-INT-ET is booted, has started a communication with the router and with the 831.

    4.    Start SLM-Utility-G3 V2.110 or later
Go to “Connection” » Remote » Internet and enter the next available IP address (in this case



b)     Click “Connect”

The SLM Uitlity-G3 program will quickly locate the 831 because of the shortness of the cables.

c)     You will see a screen like this:


d)     You are connected to the Model 831 via the Model 831-INT-ET Docking Station and the router.

Connection Photo

The AC adapters are not shown.                 

The BLUE CAT5 cable goes to the PC (PC not shown).

The USB cable between 831 and 831-INT-ET must be installed for before the 831-INT-ET system boots






What does the communications watchdog in the 831-INT-ET do?

Communication Watchdog Overview


The Model 831 and 831-INT-ET have features to monitor the USB communication between the two devices and if there is no communication for one hour, the Model 831 and 831-INT-ET will automatically power cycle.


Requirements for this feature

  • 831 firmware V2.11 or later
  • 831 board revision D or later
  • 831 run mode = Continuous
  • 831-INT-ET firmware V1.0 or later




Communication Watchdog Description 

When an 831 matching the requirements above is placed into an 831-INT-ET, the 831-INT-ET automatically sends a command to the 831 that enables the communication watchdog.  When an 831 is removed from the 831-INT-ET, the communication watchdog remains enabled but becomes inactive.  To disable the watchdog, go to Tools -> Communication -> Status and uncheck Communications Watchdog at the bottom.


If the communications watchdog triggers a power cycle, the system will turn completely off and in approximately 1-2 minutes turn back on.  A communications watchdog event produces records in the 831 Session log that show a stop due to IO and a run approximate 1-2 minutes later.


WARNING:  The 831 does not differentiate between an 831-INT and 831-INT-ET.  If an 831 has been placed in an 831-INT-ET and then later removed and placed in an 831-INT, the communication watchdog must be manually disabled.  Failure to do this will cause the 831 to turn off after one hour.


For additional information, see 831 Manual page 12-24.

What are the basics for setting up the Model 831 Dynamic Trigger?

When setting up the 831 to log exceedances, you need to specify a trigger method:




 - LEVEL – this is straightforward, simply the level at which an event is triggered.

The trigger is defined at the first level reached of RMS (SPL 1) and peak (Peak 1) value.

- DYNAMIC – unique feature of Model 831.



Why choose Dynamic?


Imagine the neighbor’s dog barking during the day.  Because of the amount of background noise (cars driving by, people mowing their lawn, kids playing in the yard) this would not be considered a significant

noise event. However, if that same dog were barking

at midnight, it would be annoyance.


Since the dog hasn’t gotten any louder, applying the same level trigger for the entire 24-hour measurement would not yield useful data. The plot above right shows a standard trigger situation. As you can see, some events were missed due to being below the trigger level.


This is where the dynamic trigger comes in handy. By tracking the background noise level or L90 (level exceeded 90% of the time, shown in red) and adding an offset to it (15 dB offset shown in blue) we can determine better when an event occurs.  A very useful feature for unattended monitoring applications.


Dynamic Trigger Setup


Dynamic Response Setting Number


To select the setting number, start by using the default setting (3). If you find that you’re missing events because the trigger level went up too much during an event, then make it slower and see if triggering is improved.  If you find that you’re getting false events because the background levels are changing too fast, then make it faster so that the 831 is more responsive to changes in background level.


How do I use the Vaisala WXT520 with the Model 831?

Model 831 V1.6 supports the Vaisala WXT520 weather transmitter

Next to the legacy models, we now introduce a combined weather sensor, SEN031, with ultrasonic wind sensor.

The picture and features / benefits come straight from the Vaisala brochure.



The CBL167 cable (20ft) goes from the WXT520 at one end to 3 connectors:

1)    DB9 – WXT520 signal, serial port connects to DVX008A (powered hub is not required and can be connected directly to 831)

2)    831-INT Terminal block plug – WXT520 power (5-32V) connects to 831-INT Auxiliary Power port

3)    DC Power cable socket – WXT520 heater (5-32V) connects to optional PSA027 power supply.  If heater is not wanted to save power it can be left unconnected.

 The 831-INT can’t deliver the 1.1A @ 12V = 13 W, hence the optional PSA027 power supply connection. We suggest configuring the heater only with AC powered systems.

The SEN031 mounts on TRP019 using the TRP008 and on TRP020 using the TRP021.


Typical configurations are:

  • AC power permanent: NMS016 + SEN031 + DVX008A + CBL167 + TRP008
  • Battery/Solar power temp:NMS019 + SEN031 + DVX008A + CBL167 + TRP021
  • Component:
    • 831 +  426A12-FF + CBL152 (20ft) signal + CBL154 (20ft) for power
    • SEN031 + DVX008A + CBL167 (20ft)
    • CBL140 --- connects to battery, CBL154, CBL167


The table below shows which parameters are saved in the file, “Current” is saved in the Measurement History.

    How do I access the extra signals on a Model 831 without 831-INT Docking Station?

    CBL170 Auxiliary Connection cable


    Cable connecting the Model 831 sound level meter to serial connector and coaxial DC connector (to PSA027). Serial connector: wind speed and direction, logic I/O, 2 slow ADC.


    The CBL170 consists of 3 parts:

    The high density connector (Hirose 18-pin) goes into the Model 831.

    The power is supplied via the coaxial DC connector (2.5 mm), eg with PSA027.

    Female DB9 provide the following signals:

    • 12V power
    • Logic In
    • Logic Out
    • Wind speed / tach
    • 3 A/D channels (wind direction, temperature, humidity)
    • Control GND
    • Power GND

    The cable with male DB9 and pigtails and male DB9 breakout board with screw terminals are there for convenience.


    Use examples:

     => Logic Out – Connect to relay with alarm light

     => Wind speed – as tach input (1 reading / second)

     => Wind speed / direction


    Using Logic In:


    The logic-in is not latching and is sampled by the microprocessor so for the trigger to be reliably detected, the pulse needs to remain high until sampled; at least 100ms.


    The Model 831 includes the circuitry below for signal conditioning:



    How do I calibrate a Model 831 or LxT that has a 1/4" microphone?

    When using the SoundTrack LxT or Model 831 with a ¼” pressure microphone (377B10) you also need a ½” to ¼” adaptor for the preamplifier (ADP043) and another one for the CAL200 calibrator (ADP024).

    Note: Part numbers and firmware revisions are subject to change. Please contact Larson Davis for current part numbers and firmware revisions.

    The recommended preamplifiers are the PRMLXT1 for the LxT and the PRM831 for the 831.

    The TOOLS – CALIBRATION section has different screens: Calibrate, History, Sensitivity, Certification and (in the 831 only) an E.A. Check screen and an E.A. History screen. In the sensitivity screen you select the 377B10. After calibration you will see the screens as shown on the LxT (left) and the 831 (right).

           New Peak Level shown ( 177.9 dBpk) 



    The peak overload level is the maximum level at the preamplifier that will produce an electrical overload. This level may exceed the maximum sound pressure level the chosen microphone is capable of measuring. Please consult the microphone data sheet for the maximum level for your microphone.

    The sequence below shows how to move from the ½” microphone to the ¼” microphone, during the calibration. Sequence of screens (LxT) when changing from ½” free-field microphone (377B02) to a ¼” pressure microphone (377B10).

    Sequence of screens (831) when changing from ½” free-field microphone (377B02) to a ¼” pressure microphone (377B10)


    The Calibration outside normal range message may or may not appear depending on the nominal sensitivity (user selectable in the 831). Refer to the manual where the valid range is shown. This warning is intended and allows to detect a larger than normal change. There is no problem in accepting the change. (If you recalibrate with a 50mV/Pa microphone, your reference will be again the old one).

    How do I use the Reference Curve Editor in DNA?

    DNA Reference Curve Editor


    There are numerous examples of references curves, yet the most popular one is probably the

    equal loudness curves, see below.


    DNA stores the reference curves in the DNA4/Weight directory as “CRW” files.



    The files are defined using the Reference Curve editor from DNA (DNA4/RefCrv.exe) and placed on the graphs using the “Ref Curve” tab of the graph properties.



    Working principle of Reference Curve:

    • One curve is the reference, the others are derived from it.
    • You can draw the curve by hand or adapt it by hand
    • You can enter the values in a table
    • You can copy and shift a curve



    Selection Icons   

    • Selection » Select a point or a curve, black point indicates the curve is selected, empty larger square indicates the X value is selected.
    • Select X »

    Curve Icons  

    • Add curve – allows you to add a curve parallel to the selected one, by clicking on the graph to attach it to a point. This continues until you select another button.
    • Add point
    • Delete point


    When you want to delete for example a point of 100 Hz for all curves, use the combination with the X-selection as shown below:



    Graph icons     

    • Zoom all » Unzoom
    • Zoom window » Select a portion to zoom in 2 directions
    • Zoom X » only zooms the X-axis
    • Zoom Y » only zooms the Y-axis



    The standard MS Windows commands or those already mentioned as icons are not discussed here.


    Edit Menu

    • Select All » selects all points on a curve. Use this to move the complete curve.
    • Edit numbers » edit numbers on each curve as well as the reference value.


    • Curve Properties »Menu


    • Graph Properties » Menu                             Also via “Right Click – Properties”


    Tools Menu

    • Offset » Move the curve up or down (negative value)
    • X Axis Lin. <-> Log. » Toggles between linear and logarithmic X axis. It is recommended to do this before you start.

    View Menu

    • Point Inspector


    This allows you to enter the Label (make sure to press ENTER or the value is not registered) and the Ref value.


    If you click on a point on the graph or on the frequency arrows you will see the right screen. This does not allow you to change the values.


    About the reference, you need to have all the values either in increasing order (top to bottom) or in decreasing order (reverse).




    The graph on the left has no reference curve, while the one below has the reference curve added.

    Can I have a 4-20mA output from the sound level meter?

    Using the AC/DC out from the Model 831 or SoundTrack LxT you can convert the DC signal to a 4-20mA signal using the IMI 682A06 Universal Transmitter, with optional display 070A80.


    The setup requires the following:


    • Jack output: AC/DC
    • CBL139 has the DC signal on the white connector
    • DC signal is linear with dB as 0 V » 0 dB and 1 V » 100dB
    • Connect DC signal to ports 42 (V-) and 44 (V+)
    • Connect AC power to 682A06 via ports 31 and 33
    • Short ports 11 and 12
    • Ports 13 and 14 have output signal.


    Complete setup

    The 682A06 allows for a 2-point calibration, via the ADV SET » CAL » CAL LO / CAL HI / USE CAL screens.

    How does QC Tonality work and what are “Corrected dBA”?

    QC Tonality


    In the OVERALL tab, the QC Tonality screen will appear after the 1/1 octave screen if:

    • The option is enabled (See Tools » About » Options)
    • 1/1 Octave bands are computed
    • Z-weighting is selected for OBA


    1/1 Octave in OVERALL             QC Tonality                              Options Display


    The QC Tonality algorithm proceeds as follows:

    • Search high value frequency band in the range [31.5 16000] Hz
    • If the level > average of adjacent bands, then add 5 dB
    • For the end bands, if level > 5dB than next band, add 5 dB
    • Apply A-weighting to spectrum [31.5 16000] Hz
    • And display value as Corrected dBA

    In the example displayed above there are two bands with a correction, 31.5 Hz and 500 Hz, which are both greyed out.


    Note for the 31.5 Hz it only looks at the 63 Hz band and not at the 16 Hz since it is outside of the analysis band.

    What firmware options and accessories will my Model 831 support?

    Required Hardware and Firmware for listed Features

    Brief Feature Description

    • 32 MB Internal DRAM – Internal dynamic RAM double from 16 MB to 32 MB.  Model 831’s with 32 MB DRAM will not run firmware versions prior to V2.20
    • 831-INT-ET Watchdog – A feature that will reboot the Model 831 and 831-INT-ET when there is a USB communication failure, the Model 831 becomes unresponsive, or the 831-INT-ET crashes
    • Clock accuracy improvements – Internal clock accuracy improved to < ±10 s/month drift
    • Timers power on 831 – A feature that allows daily timers to automatically turn on the Model 831 power just prior to the set start time.
    • 831-FFT – FFT firmware option
    • Z-MODEM download – Firmware feature that provides a data transmission protocol with data validation and automatic retries for back packets

    How do I update the firmware in my model 824 sound level meter?

    Please follow the instructions below to upgrade the System 824 firmware. Before

    applying this procedure you will need to obtain the firmware file (ld8-xxxx.rom) and

    authorization file (824-xxxx.ldk), by contacting Larson Davis technical support at contact

    information listed in the footer of this page.


    Initial Setup

    1. Power down the computer and the 824.

    2. Connect an available RS-232 serial port on the PC to the 824 via CBL006 cable.

    3. Turn the computer on, then the 824.

    4. On the 824, press Setup, select SLM ISM, then press the checkmark. Then press TOOLS, and select Communication, then press the checkmark, and set the baud rate to 9600.

    5) .Start the 824-Utility software v3.12 on your PC.


    1. Under the software’s File menu, select 

    Connect or press the tool bar icon.

    2.  Enter the COM port, and 9600 Baud Rate of your 824. Press Connect.

    3. Your instrument will connect and its serial number and revision will appear on the

    Title tab window.

    Upgrading Firmware

    1. Under the File menu, select    

    Upgrade…,then browse to your 824-xxxx.ldk file.

    2.  Put a check mark in the Apply Firmware box, and press Start. The upgrade will take a few



    during the process.

    3. Once the upgrade is complete, verify that the 824 has a new revision in the TOOLS,

    About-a screen shown below.

    4. If you purchased new options, you may either select both the firmware upgrade and

    options upgrade boxes or repeat the procedure, selecting Apply Options in step

    2 above. The Apply Options function will only take a few seconds.


    Contact Larson Davis Customer Service at or (888) 258-

    3222 if you have any questions regarding your upgrade.


    If my 824 shows Analog Cal Bad, how do I restore the Analog Cal values?


    A change of internal 824 memory may cause the message ‘Analog Cal Bad’ to appear. 

    824 Maintains factory calibration offsets in flash ROM

    The ‘analog cal bad’ can usually be field reprogrammed in the model 824.


    • Internal to the 824 are stored values in EEPROM memory to digitally correct any slight calibration offset errors (typically less than 0.2dB) in the SLM ISM option for the full 110dB dynamic range.
    • If the stored values no longer match the checksum, the 'Analog Cal Bad’ message is displayed.
    • Call the factory Technical Support 888-258-3222 in the US or, 716-926-8243 international, with your 824 serial number to receive the necessary calibration file by email.

    Email Download Example:  Attached are the original offset values for 824 snxxxx to reprogram:


    1) Copy the attached file .CBK to your 824Util (v 3.12) software folder on your PC.

    2) Run 824Util and connect to the 824

    3) In 824Util Select File, Upgrade, Firmware/Options

    4) Browse and click on the 824axxxx.cbk

    5) Check on Apply Firmware, Press Start

    6) After completion of reprogramming, do a microphone SPL calibration, and then store to EEPROM using TOOLS, MEMORY, Create EEPROM Backup.


    The contents of a calibration file .CBK for model 824 sn 3104 is :

    Dump of Cal Block for 824:A3104

    Version: 5

    CalOffset: -47.0781

    Bias_OS: -0.0039

    TEMPOFFSET: 58.0586

    HighDynRangeOS: -0.3004

    ChanWghtOS: -0.2500

    How do I Install new firmware and/or options on Model 831, SoundTrack LxT®, SoundExpert LXT and 831-INT-ET?

    Please follow the instructions below to upgrade firmware and/or options on Model 831, SoundTrack LXT® or SoundExpert LXT.


    Updating to the latest version of SLM Utility-G4 PC-Software

    1.     Go to /support/soundlevelmetersupport/Model831.aspx

    for the Model 831 or /Support/SoundLevelMeterSupport/LxTSoundLevelMeters for the SoundTrack LXT® or SoundExpert LXT and download the most recent version of SLM Utility-G4.


    Download the G4_Installer_x64.exe for a 64 bit operating system, or G4_Installer x32.exe for a 32 bit operating system (to check to see what operating system you have, go to Start, Control Panel, System).

    Note: Make sure you have full admin rights before starting the installation process, otherwise the drivers will not install correctly.


    2.     Download and save the file to your computer.

    Note: If the path to the file is longer than 128 characters the Windows operating system may generate an error.  You will have to move the zip file to a location with a shorter path name.


    3.     Disconnect any Model 831 or LxT that is connected to the PC.


    4.     After the file is saved, find the zip folder (on the location you chose on step 2) and right click to select “Extract All”. After the file is extracted run the installer file.

    5.     Follow the wizard instructions to install SLM Utility-G4 on your PC.


    6.    Upon completion of the install, you will see the SLM Utility-G4 shortcut on your desktop.


    Connecting the meter to the computer

    • Connect the USB cable from the meter to the computer and turn the meter on.
    • When using Windows XP, the Found New Hardware Wizard will appear. If prompted, do not search Windows Update for the driver. Select Install the software automatically.
    • When using Windows 7 and 8, the driver will install automatically. It can take several minutes for the driver to install.
    • Click Next, then Finish.

    Updating firmware rev. in Model 831, SoundTrack or LXT SoundExpert LXT® using SLM Utility-G4

    • Warning: The upgrade process will cause all data and setups stored within the sound level meter to be
      lost.  Using SLM Utility-G4, save any data or setups you have in the meter before upgrading.
    • Warning: Loss of power during firmware upgrade may leave the instrument inoperable.  As a consequence, leave the sound level meter connected to the PC and don’t remove the cable until loading new firmware has completely finished.
    • Note: If you are using an 831-INT-ET docking station you will also need to update its firmware. If you upgrade the 831 by connecting through the 831-INT-ET docking station, the 831-INT-ET firmware will be updated automatically.


    1. Run SLM Utility-G4 software.
    2.  Click File > Upgrade Instrument.
    3. Connect to the meter and follow the on screen instructions until you reach the screen where the firmware file is selected and ensure that “Upgrade the firmware using a .ROM file” is selected.
    4. Click the Browse button and select the firmware file appropriate for your instrument (either the 831 or LxT file); click Open.
    5.  Follow the wizard instructions to complete the firmware upgrade process. 

    Installing new firmware options in Model 831 and SoundTrack LXT® using SLM Utility-G

    • Follow steps 1 and 2 of the instructions for upgrading firmware rev.
    • Select “Change Installed Options using a .OPT File” checkbox and browse to the location where you have stored the .OPT file.
    •  Follow the wizard instructions to complete the new firmware option installation process.


    NOTE: An options file is linked to the serial number of an instrument and is typically emailed to you after order placement, Make sure the meters serial number and .OPT file serial number match before continuing.


    SLM Utility-G4 cannot find my sound level meter because the sound level meter will not fully boot.  If your sound level meter will not fully boot try the following step

      1. While instrument is booting and the banner icon is in the middle of the screen, press and hold Stop, Reset and Enter simultaneously for 5 seconds to reformat the internal memory.
        • WARNING – this will cause any data stored in the sound level meter to be lost
      2. While instrument is booting and the banner icon is in the middle of the screen, press and hold Tools and Enter simultaneously for 5 seconds for the instrument to stop booting for 2 minutes.  During this 2 minute period, you can use SLM Utility-G4 to load new firmware following the steps outlined in Installing firmware in Model 831, SoundTrack LxT® and SoundExpert LxT using SLM Utility-G4
    Why can I not connect to a meter when Using SLM Utility G4 or G3?

    If SLM Utility G4 (any version) or SLM Utility G3 version 2.300 or later is unable to connect to a sound level meter, there are two potential causes.

    Cause #1 – The USB driver for the Model 831 or LxT sound level meter is not correct

    1.     To check for the correct driver click the start icon and in search type device manager then press Enter to start the device manager.  

    On a Windows 8 PC

    a.     Open the Charms Bar by dragging the cursor to top right of the screen or by pressing Win + C.
    Select Settings and then Change PC settings.
    Select the Devices under PC settings application.

    2.     Using a USB cable, connect the sound level meter to the computer making sure the meter is powered on and fully booted.

    3.     In the list of devices, find the item Larson Davis USB device and expand the list to show the devices

    4. On the device Larson Davis Model 831 & SoundTrack LxT, right click and select Properties

     5. On the properties page, the driver manufacturer should be libusb 1.0

    6.  If the driver manufacturer is “libusb 1.0” and you cannot connect then proceed to Cause #2.  If the driver something different like motusb.dll then uninstall the SLM Utility G3 and/or G4 software then reinstall.  Make sure that you install by running LDsetup.exe and that you have administrator rights.

    Cause #2 – The USB hardware driver needs an update

     This problem only occurs when using a USB 3.0 port with drivers from certain hardware manufacturers.

    7.     Verify that connected port is USB 3.0.  This can be done one of two ways
                a.   If the internal portion of the connector is blue, the port is USB 3.0

                b. Within device manager, expand the Universal Serial Bus Control and look for a port name that includes Renesas Electronics USB 3.0 in the name

    8.     If there is a Renesas Electronics USB 3.0 device or device manager shows a device that is unknown and doesn’t have a driver, the USB 3.0 driver needs to be updated.  This driver is provided by the manufacturer of the PC or motherboard.  Normally, you can find the driver with instruction for updating if you google the manufacturer and model of the PC + USB 3.0 driver.  For example, I would google Lenovo T420s USB 3.0 driver.


                9.     Follow the manufacturer’s instructions for updating the driver and you should now be able to connect.  If a workaround is needed, any available USB 2.0 port will work.








    What is the difference between the Model 831, SoundExpert LxT and SoundTrack LxT?

    What are the 831 and LxT key functions during instrument boot up?

    Why does the sum of filters not always match the overall reported level?

    The reason is due to the fact that what you are calculating when you sum the values of the 1/1 and 1/3 Octave bands is not an overall level. This number is simply the summed level of the 1/1 or 1/3 octave bands. This is best characterized in the plot below:

    This means that when adding up the 1/1 and 1/3 octave bands, the frequencies at or around the cutoff frequencies of the filters will have a slight error. This is why these numbers can not be used to accurately calculate the overall sound pressure level. Even more error is seen when performing a Weighting after Filtering, as seen below.

    When applying weighting curves via postprocessing, the attenuation at the cutoffs of the Octave Filters in addition to another factor can cause even greater error. As an example, applying the attenuations of an A weight filter by hand will not likely yield the same results as running the raw data through a filter, and calculating the overall level. The plot below shows the error on these calculations:

    So if a frequency is close to the cutoff, the attenuation applied by simply subtracting it from the 1/1 or 1/3 octave band may be off by as much as 15 dB off. This creates an even larger difference between the Overall Level and the 1/1 and 1/3 Octave Sum.

    How can I temporarily disable purchased options on my 831 or LxT?

    Options Masking on Model 831 and SoundTrack LxT


    Using the SLM Utility-G3 you can “mask” installed firmware options to simulate other instrument configurations. The mask can also be controlled on the instrument in tools -> System Properties -> Options tab. This is a handy tool for customer demonstrations or technical support, when you wish to configure an instrument with certain options.


    Here is how you do it. In the System tab, select Mask Installed Options.

    This leads to the following screens where you can, for example, uncheck flags to have only LOG + OB3 + SR.


    Next you UPLOAD mask.

    Close the window, disconnect G3, turn off the 831 and reboot it. When you reboot and reconnect to G3, check to see that the MH / ELA is turned off. Re-establish the options with the reverse procedure or a “Format/Restore Defaults”.  This will enable all purchased options.

    How can I get my instrument calibrated quickly?

    Rush Service Orders Option


    Applicable products: ALL service orders (CER-xxx)


    CER-RUSH gives you top priority for service orders

    • $50 flat fee for each item on the order
    • Most CER items are shipped within 24-hours of receipt of product.  An exception is items that require environmental testing which can take to 2 to 4 days to complete
    • Product will be returned to customer as specified on the order.  For a quick return, be sure to specify a fast shipment method.
    • CER-RUSH orders will be processed in the order received
    What operating system will run my Larson Davis software?

    Windows 7 & 8 Compatible software

    Windows 8 installation notes


    Some software requires a library from Microsoft, VC Redistributable, to be installed prior to installing the Larson Davis software.  When using Windows 8, the user is required to reboot the PC after installation of this software component.  When prompted to reboot, select yes.  Failure to reboot will cause an SLMserver.dll installation error to occur although a reboot will clear this up.  After rebooting, the installation will automatically restart and finish.


    For DNA to install properly, SLM Utility G3 must be installed first


    XP mode is not available for Windows 8 but there are other, third party products available to create a virtual PC if support is needed for old software like SLM Utility (812/820).  One such option is Virtual Box, , that is available for free.  Once virtual box is setup, then a legal copy of Windows XP still needs to be installed.

    Which unsupported operating systems are known to have problems and not work?

    • Windows XP Home and Starter Editions
    • Windows XP 64-bit, any edition
    • Windows Vista Home Basic, Home Premium and Starter Editions
    • Windows 7 Home Basic, Home Premium and Starter Editions

    XP Mode Notes

    Download and install Windows XP Mode, .  This is a large download, approx 500 MB but once installed, these programs will work

    • 824 Utility connected using DVX008A
    • AUDit 2.1 connected to 824 using DVX008A
    • SLM Utility connected using DVX008A

    When Installing Windows XP Mode there are instructions at the link above but key things to know

    • There are 3 files to install
    • Once downloaded and installed, let Windows Update run on the virtual XP machine so it becomes current before installing LD apps
    • After starting the Virtual XP machine, you must install the XP version of the driver for the DVX008A.
    • On the top menu select USB and click on USB Serial Controller Attach.  This tells Windows7 that the virtual XP machine is using the DVX008A
    How do I get my Larson Davis product calibrated?

    Larson Davis offers a comprehensive factory calibration for our products to ensure that your instruments continue to operate in compliance with published specifications


    With CAL+ calibration our customers receive

    •  Labor warranty extended for 1 year                                                  
    • A2LA and ILAC accredited testing
    • 5 to 10 business day turnaround standard
    • Extensive testing for excellent test coverage
    • Firmware upgraded to latest version
    • Worn consumables replaced at no charge

    Follow these instructions to return your Larson Davis product for factory calibration.

    A)      Gather the model and serial number of the products to be calibrated

    B)       We will attach a sticker to the product(s) showing when the item was calibrated and when the next calibration is due. As part of our ISO 17025 accreditation, the equipment owner must tell us when the next calibration is due.  Please specify the calibration due date in order to avoid delays while we ask for this information. 

    The due date can be a specific date or something like “in one year” or “in two years”.  Larson Davis recommends factory calibration once per year.

    C)       Contact us at +1 716 684 0001 or to request an RMA number

    D)      Provide the following information

    a.       Model and serial number of items to be calibrated

    b.       The calibration due date

    c.        Return shipping address

    d.       Return shipping instructions (carrier and type such as overnight, ground, economy air, etc.)

    e.       Product owner name and address that will be printed on the calibration certificate if different from the organization ordering the calibration

    E)       Provide a purchase order (PO) or call to pay by credit card

    Note: Expedited calibration is available for an additional cost.  Please contact us for more information.

    See the /service/calibration.aspx for terms and conditions of CAL+ service

    How do I install Blaze Software and Infrared Interface Drivers?

    GENERAL Blaze V6.201 or Later Installation

    Make sure you have full administrator rights before starting the installation process, otherwise the drivers will not install correctly.

    Retrieve Blaze V6.201 and drivers from the Larson Davis Website go to /support/SoftwareProductsSupport/blazesoftware.aspx  and select the correct file for your system either a 32 Bit or 64 Bit (see Below):

    To find out what System type you have, click on the Start Menu, select Computer, then right click on Computer (right column) and select Properties or select
    .  Look under System, to find what System Type you have and select the correct zip file. (Example below)


    For the example above you would select  for this computer. Click and Save As to your Desktop or where you would want the file stored.


    You will find this icon on your Desktop.



    All instrumentation that is connected to the computer must be disconnected prior to installing Blaze. 

    You must extract all files from the zip file before installing it. Click on the zip file folder

    Then Click Extract All Files 


    Once you extract the files, you will have these file options

    To install Blaze Software and drivers double click on the extracted setup.exe file (Application).

    NOTE: Do not select Windows Installer Package (see below)

    Follow the prompts to install the program, and let it install in the default folder.  Below are a few pop-up screens of interest as you go through the installation:

    You will need a Serial Number– if you don’t have your serial number, please call Larson Davis Tech Support at 888-258-3222

    Infared Driver Interface Installation DVX009 and DVX010

    Prompts to install DVX009 and DVX010 drivers, click Yes.

    Software from Silicone Laboratories will appear, follow the prompts and continue through the installation process.

    Follow prompts and don’t forget to check launch the CP210xVCP Driver Install

    If this appears in the install, you may have had an Infrared (IR) device previously installed on your computer. Click option Repair then click on Next.

    You may be asked to restart your computer DO NOT restart your computer when asked during the IR download.  The Blaze install is still not completed. You can restart your computer manually after the Blaze install is completed.


    After Blaze is installed, plug in the InfraRed (IR) interface (DVX009 or DVX010) into the USB port.


    Allow the computer to automatically install the driver.  (If a prompt appears and asks to have you let the computer search Windows Update for the driver, click CANCEL, this is a very long process and the Blaze software will automatically recognize the driver and install it).



    Once the driver has been installed, it will show that the driver software has been installed successfully.



    Remember what COM Port the device is specified at for when you open Blaze as you may need to specify the COM port your InfaRed (IR) devise is located at.

    How do I upgrade the firmware on my HVM100?

    This FAQ outlines the procedure for using Blaze Demo to update HVM100 firmware to version 1.33.


    Required Items

    • HVM100 to be reprogrammed
    • Not required: Set baud rate to 115.2k for faster detection and reprogramming
    • CBL006 serial cable
    • Use DVX008A to program using a USB port on the PC
    • Fresh batteries in HVM100
    • Blaze V6.1 or later demo version which can be downloaded from /softwareproducts/blaxesoftwaresupport.htm 


    1. Upgrading firmware will cause any data stored on the HVM100 to be lost.  All data should be downloaded prior to upgrading firmware
    2. Do not disconnect power while reprogramming firmware.  This can render the HVM100 inoperable and require factory service.


    1. Put fresh batteries into the HVM100 and turn the HVM100 power on
    2. Connect CBL006 between HVM100 and PC.  If using a DVX008A USB to serial adapter, make sure the assigned serial port is less than COM14
    3. In Blaze demo, select Options > Connection
    4. For instrument type, select HVM then Connect
      1. Blaze demo uses a virtual HVM100 for demo purposes so COM port and Baud Rate selection don’t matter on this dialog
      2. Note: this does not actually connect to the HVM100 and is used only to enable the HVM100 instrument manager



        5.     In the HVM100 instrument manager, select Manual Control then Upload HVM100 Firmware which will start the firmware upgrade program.



        6.    On the first dialog, select Next

        7.    On the second dialog, check automatically detect communication settings

      1. Note: it may take several minutes for the automatic detection to complete

        8.     If the HVM100 is found, a menu with language options will appear.  If the HVM100 is not found, verify the CBL006 is connected and the assigned COM port is less than COM14.


        9.    Select the desired language set and the Finish.  The HVM100 will begin to reprogram the firmware and ask you to turn the HVM100 off then back on.  Once this is completed, check the box and select OK



             10.     Once the message below has been displayed the firmware upload is complete and by pressing the on/off button the HVM100 will resume normal operation.


    How do I prevent trouble in the field when using Spark dosimeters?

    The Larson Davis Spark® Series multiple dosimeter system usually consists of the 706RC Dosimeter Remote Controller / Sound Level Meter and multiple 703+  or 705+ Personal Noise Dosimeters. NOTE: For the duration of the troubleshooting guide, the text, to avoid duplication, will only refer to the 705+; however the 703+ functions are identical to that of the 705+ and all recommended suggestions apply.


    The 706RC has an LCD Display and a keypad for controlling and reading out data from the 705+. Use of these devices to obtain and report worker noise exposure data is usually straightforward and relatively simple, however, as with any system, unusual circumstances may result in actual or perceived fault conditions. The purpose of this document is to help guide you though any anomalous conditions or behaviors which may prevent the proper calibration and use of the system in the field.



                             706RC         705+           703+                    


    The units shown above work together to form a dosimetry system whereby the 705+ personal dosimeter is able to be calibrated, controlled, and viewed by the 706RC remote control unit. This offers the utmost in reliable operation and good sampling results as the subject under test has no controls or display on the dosimeter with which to interfere, nor any visual indication of data to try to influence the results. It also allows the instrument operator to stand a comfortable distance away from the worker while starting / stopping the data gathering, viewing and verifying data, logging status, battery capacity, etc. throughout the day. It is also possible to use the 706RC independently as a simple Sound Level Meter with an optional rigid microphone assembly (MPR002)


    Five possible types of failure are covered in this Troubleshooting Guide:


    • Dosimeter does not connect or communicate
    • Dosimeter does not calibrate or microphone is damaged
    • Dosimeter does not take data or data cannot viewed / retrieved
    • System does not respond as expected to operational commands by the user
    • System appears ‘dead’ or unresponsive – no power; “frozen” or “locked up”


    Glossary of Terms used in this Guide:



    Sleep Mode: Unit is powered (battery is installed) but unit is not measuring or taking data. This is indicated by a single LED blink every five seconds. The dosimeter is using very little power in this mode and may be shipped / stored while in sleep mode. When a 706RC is present and sending the ‘connect’ signal to the 705+, it will come out of the sleep mode


    Power Up Mode:  Unit is being powered after having the battery removed for an extended period of time. This is indicated by a simultaneous illumination of both the green status LED and the red power LED. This mode may last from 1 to several seconds depending on the amount of memory which is already being utilized for data storage in the dosimeter.


    Awake Mode: Unit has been awakened by the ‘connect’ command issued by the 706RC and is ready for calibration, measurement and calculation of data values.


    Connect Mode: Unit is being awakened by the 706RC. This is indicated by a simultaneous illumination of both the green status LED and the red power LED. This mode may last from 1 to several seconds depending on the amount of memory which is already being utilized for data storage in the dosimeter


    Running Mode: Unit is measuring noise dose and taking data. Indicated by a fast blink of the green ‘status’ LED


    Power Critical Mode: Unit has virtually no battery capacity remaining and cannot perform any function. This is indicated by a single illumination of the red power LED every ten seconds.




    Envelope Icon:  Indicates the 706RC is communicating with, controlling and receiving information from the 705+. All information viewed on the 706RC display is coming from the 705+ dosimeter while the envelope display is flashing.


    Check Key:  The check key is located in the very center of the 706RC keypad and behaves very much like the ‘Enter’ key on your computer. Also, use the check key to acknowledge any message on the display screen which says “OK”


    Reset Key: is located in the lower left hand corner of the 706RC keypad; it is used for clearing the overall test results from the display screen. It also behaves like the ‘Esc’ key on your computer, and is a means for reversing to previous menus or display screens


    Possible individual faults preventing proper field sampling operations:

    1. Unit does not turn on:


    Model(s) affected: 706RC

    Indicated by: no response when on button is pressed (706RC) no LED has illuminated over a more than 10 second period (705+)

    Probable cause: Batteries ‘dead’ or not installed

    Recommended fix: Replace Batteries w/ 2 each AA Alkaline cells, by loosening the latch at the top of the battery door and lifting off the cover. Be sure to observe the battery polarity (+ and -) markings in the battery compartment as installing the batteries incorrectly will cause the unit to fail and no longer be operable. If the new batteries do not fix the problem, (and they are known good batteries) then the unit will need to be returned for repair. (Note: do not replace batteries in a Hazardous Location as defined by NFPA code)


    2. Unit does not turn on:


    Model(s) affected: 705+

    Indicated by: No LED has been observed to illuminate over a more than 10 second period (705+)

    Probable cause: Battery ‘dead’ or not installed (Note: 703+ uses 2 ea. AA cells)

    Recommended fix: Replace Battery w/ 1 each AA Alkaline cell by loosening the screws on the battery cover. Be sure to observe the battery polarity (+ and -) markings in the battery compartment as installing the battery incorrectly will cause the unit to fail and no longer be operable. If the new battery does not fix the problem, (and it is a known good battery) then the unit will need to be returned for repair. (Note: do not replace batteries in a Hazardous Location as defined by NFPA code)




    3. Unit (705+) does not connect to 706RC within a few seconds


    Model(s) affected: 705+ and 706RC operating together

    Indicated by: Display of 706RC reads: “Searching for Any 70x” or “Searching for Serial number 41nnn” (n=some number)

    Probable cause: a. Infrared ports are not aligned properly or 706RC is too close or too far away from the 705+ (optimal distance is 1-3 feet) b. battery (ies) are too low in either 705+ (most probable) or 706RC (less probable) to transmit IR signal c. there is interference with other 705+ dosimeters in close proximity d. there is interference with other IR sources or reflection of the IR beam

    Recommended fix: a. Try moving the units closer to or farther away from each other. b. replace batteries c. physically relocate other dosimeters, turn them away from the 706RC, place in storage case, etc. d. eliminate other IR sources or shield the 706RC and 705+ from the direct effect of other IR sources. If the units are resting on a highly polished table or a sheet of white paper, reflections from the surface may affect connection or even cause the units to ‘freeze’


    4. Unit does not allow Calibration:


    Model(s) affected: 705+ Dosimeter

    Indicated by: Displayed error message: “Must RESET First OK(see Fig.1)  

    Probable cause: Dosimeter must be reset before Calibration can take place

    Recommended fix: Press ‘Check’ key to erase error message, then press reset key three times until you see “ Reset Overall? YES NO” Press Check key once, then ‘tools’ key to return to Calibrate screen. Proceed with Calibration as normal. NOTE: If dosimeter does not respond or appears to be reset, yet will still not allow Calibration, see 7. below


    5. Unit does not allow Calibration:


    Model(s) affected: 705+ Dosimeter

    Indicated by: Displayed error: “Must STOP and RESET First OK  

    Probable cause: Dosimeter must be stopped (from taking data) and reset before Calibration can take place.


    Recommended fix: Press ‘Check’ key to erase error message, then press RUN key once, then press RESET key three times until you see “ Reset Overall? YES NO” Press Check key once, then press the TOOLS key to return to Calibrate screen. Proceed with Calibration as normal.


    6. Unit does not Calibrate / Calibration fails:


    Model(s) affected: 705+ Dosimeter

    Indicated by: ! in upper left hand corner of display on calibrate screen when connected to the 706RC. (This will also be seen in the lower part of the display accompanied by the word “LOW”. See 4. for normal Calibration process)

    Probable cause: a. Calibrator is not turned on, b. microphone is not placed in the opening of the calibrator, c. calibrator output is incorrectly selected, or d. microphone not connected or is malfunctioning.

    Recommended fix: a. Press round ‘ON’ button on side of CAL150 calibrator to turn it on. (see Fig 2). Note: calibrator will turn itself off after 90 seconds in order to save battery power. If calibrating multiple dosimeters, it may be necessary to press the on button again) b. Make sure the microphone is firmly placed into the opening if the calibrator adapter; there is an “O-ring” seal in the inner diameter of the calibrator adapter and this may require firm force to seat the microphone all the way into the adapter opening. c. There is a miniature slide switch on the calibrator housing (the same side of the case as the ON button). Make sure this ‘dB Level’ switch is in the “114 dB”  position (pushed all the way towards the end of the calibrator which has the microphone opening. d. Make sure the silver microphone connector is fully seated in the mating receptacle in the top of the dosimeter. If it is fully connected and still indicating ! or ! LOW on the calibration screen, then the microphone is most likely defective and should not be used. To verify this, take a different microphone and substitute it for the malfunctioning and proceed with calibration procedure. If the calibration is successful then it is the first microphone which is at fault.


    7. Unit appears ‘frozen’ and does not respond to commands


    Model(s) affected: 705+ Dosimeter

    Indicated by: Display prompt on 706RC is asking the operator to “first Stop and Reset” even though 705+ dosimeter is not running / no data are present.

    Probable Cause: Unit has had some interference and/or interruption of infrared control most likely caused by having multiple dosimeters in close proximity to each other while attempting communication or control by the 706RC.

    Recommended fix: Remove the battery from the dosimeter and set it aside for at least five minutes, then replace the battery and observe the dosimeter as it indicates it is going through the Power Up mode (see Glossary). This action will perform a complete system reset of the dosimeter – NOTE: you must check the date and time and reset it if has been changed back to the default settings (1/1/08 and 00:00:00) due to loss of power.


    8. Battery Capacity insufficient for full shift monitoring:


    Model(s) affected: 705+ Dosimeter

    Indicated by: trouble connecting; sluggish response, Red battery indicator LED  is illuminating once or twice every three seconds; red LED is illuminating once every ten seconds; no LED has illuminated over more than a 10 second period

    Probable cause: Battery almost ‘dead’ or ‘dead’

    Recommended fix: Replace the battery with a known good battery. (Note: do not replace batteries in a Hazardous Location as defined by NFPA code)


    9. Unit does not display correct date or time:


    Model(s) affected: 705+ Dosimeter

    Indicated by: displays incorrect date and time

    Probable Cause: battery is ‘dead’ or has been removed from dosimeter for a period of time

    Recommended fix: Reprogram correct date and time by using 706RC to enter correct date and time manually or connect 705+ dosimeter to the PC using Blaze software. (Once connected, the Blaze s/w will automatically synchronize the date and time to the settings of the PC)


    10. Unit displays ‘Mic Fault’


    Model(s) affected: 705+ Dosimeter and 706RC

    Indicated by: displayed error message: “MIC FAULT OK

    Probable Cause: a. microphone is not connected b. microphone was unplugged by the worker during the test and plugged back in c. microphone is malfunctioning

    Recommended fix: a. plug in microphone, press ‘Check’ key to erase error message. (Note: alarm bell indicator will remain on the display to let you know this unit had experienced a mic fault) b. press ‘Check’ key to erase error message. c. substitute a different microphone and recalibrate before further use


    Illustrations referred to in this Guide:



                               Fig. 1:Must RESET” message                          FIG. 2: Calibtrator Controls




    How do I install firmware options into an HVM100?

    This document contains instructions on how to establish a Hyper-Terminal connection (serial port) with the HVM100. If you have already established this connection, skip to the command instructions sent with your serial number specific options.

    Establishing a Serial Port Connection Using Hyper-Terminal

    A. Turn on the HVM100 and set its baud rate to 115.2k. Connect the CBL006 cable to the HVM100's serial connector and to the PC's Com1 serial port.


    B. Use Window's Hyper-Terminal to establish connection to the HVM100. Hyper-Terminal is found in Windows by selecting "Start", then "Programs", then "Accessories", then "Communications", and then "Hyper-Terminal".


    C. Once Hyper-Terminal starts, you will be asked to "Enter a name and choose an icon for the connection:". Type "HVM100" for the name, and select one of the available icons. Then press OK. See Figure 1 below.



    Figure 1: Type HVM100, select and icon, and press OK.

    D. Hyper-Terminal will then open a window titled "Connect To". In this window select "Connect using: Direct to Com1", and then press OK. See Figure 2 below.



    Figure 2: Select “Direct to Com1” and press OK.

    E. Hyper-Terminal will then open a "COM1 Properties" window. Setup Hyper-Terminal as shown in Figure 3 below and then press OK.

    Figure 3: Setup the COM1 properties as shown above and press OK.

    F. Next, from the main menu in Hyper-Terminal, select "File" and then "Properties". A window titled "HVM100 Properties" will appear. Select the Settings tab. See Figure 4 below.

    Figure 4: Select the “Settings” tab .

    G. After the “Settings” window appears, select the “ASCII Setup…” tab. See Figure 5 below.


    Figure 5: Select the “ASCII Setup…” button.

    H. After the “ASCII Setup” window appears, select the “Send line ends with line feeds” and “Echo typed characters locally” options. See Figure 6 below. Then press OK and then OK again to close both windows.



    Figure 6: Configure ASCII Setup as shown. Press OK (press OK again to close previous window).

     Once you have connected to the meter, type the commands given to you by Larson Davis to update you meter.

    Why can I not connect a meter when using SLM Utility G4 or G3?

    If SLM Utility G4 (any version) or SLM Utility G3 version 2.300 or later is unable to connect to a sound level meter, there are two potential causes.


    Cause #1 – The USB driver for the Model 831 or LxT sound level meter is not correct


    1. To check for the correct driver click the start icon and in search type device manager then press Enter to start the device manager.

    On a Windows 8 PC

      1. Open the Charms Bar by dragging the cursor to top right of the screen or by pressing Win + C.
      2. Select Settings and then Change PC settings.
      3. Select the Devices under PC settings application. 

        2.    Using a USB cable, connect the sound level meter to the computer making sure the meter is powered on and fully booted. 

        3.    In the list of devices, find the item Larson Davis USB device and expand the list to show the device  



        4.    On the device Larson Davis Model 831 & SoundTrack LxT, right click and select Properties 

        5.    On the properties page, the driver manufacturer should be libusb 1.0  



        6.    If the driver manufacturer is “libusb 1.0” and you cannot connect then proceed to Cause #2.  If the driver something different like motusb.dll then uninstall the SLM Utility G3 and/or G4 software then reinstall.  Make sure that you install by running LDsetup.exe and that you have administrator rights.



    Cause #2 – The USB hardware driver needs an update


    This problem only occurs when using a USB 3.0 port with drivers from certain hardware manufacturers.


        7.    Verify that connected port is USB 3.0.  This can be done one of two ways

        a.    If the internal portion of the connector is blue, the port is USB 3.0

                    b.     Within device manager, expand the Universal Serial Bus Control and look for a port name that includes Renesas Electronics USB 3.0 in the name 



        8.    If there is a Renesas Electronics USB 3.0 device or device manager shows a device that is unknown and doesn’t have a driver, the USB 3.0 driver needs to be updated.  This driver is provided by the manufacturer of the PC or motherboard.  Normally, you can find the driver with instruction for updating if you google the manufacturer and model of the PC + USB 3.0 driver.  For example, I would google Lenovo T420s USB 3.0 driver.

        9.    Follow the manufacturer’s instructions for updating the driver and you should now be able to connect.  If a workaround is needed, any available USB 2.0 port will work.

    How do you use the Model 831 with the 378A04 microphone & preamplifier to measure low level noise?
    The Model 831 sound level meter can be used with the 378A04 low noise microphone & preamplifier to measure noise levels as low as 6.5 dB A-weighted. This FAQ describes the necessary equipment and procedure for setting up the Model 831 to make these measurements.

    Required Items

    A complete kit with all these items except the CAL200 can be ordered using part number 831-LOWN and an existing 831 can be upgraded using part number 831-LOWN-UPG.

    Fully assembled, the 831-LOWN system looks like the systems shown below depending upon whether the flexible BNC cable is used or the rigid connector.

    How to Calibrate using the CAL200

    Important Information

    When using the 378A04 with the Model 831, the overload indication will not work properly because the 378A04 has less dynamic range than the Model 831. Measured levels above the Upper Limit documented below should be considered as overloaded. The table below documents the acceptable measurement range.

    1Typical values
    2The frequency dependent 3 % distortion limit is 80 dB for the entire frequency range and 100 dB from 10 Hz to 5 kHz.
    3The frequency dependent 3 % distortion limit is 60 dB for the entire frequency range and 80 dB from 10 Hz to 5 kHz.

    The typical dynamic range for an 831 with 378A04 is shown below

    Spectral Statistics - The Model 831 records statistical distribution data (LN) between 200 and 0.2 dB. Statistics for levels less than 0.2 dB are not computed. This does not impact the broadband statistics but has potential to be seen in spectra statistics.

    Power and Battery - Using the 378A04 with the Model 831 will decrease the battery run time by approximately 15%.

    Standards compliance - The Model 831 sound level meter when used with the 378A04 low noise microphone has not been tested for compliance with IEC 61672-1 or ANSI S1.4. Larson Davis does not guarantee compliance with all the requirements of IEC 61672-1 or ANSI S1.4 when using the Model 831 with a 378A04 microphone.

    Factory Calibration or Certification

    Because of the technology used to build the 378A04 it is not possible to perform an annual certification of the 378A04 using an electrostatic actuator, which is commonly used by calibration facilities. For this reason, annual calibrations should be performed at the factory in an anechoic environment. Contact Larson Davis for price and lead time information.


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    Telefon: +49 (0) 24 33/44 44 40 - 0


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