PCB Test & Measurement Seite 164

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PCB PIEZOTRONICS INC 716 684 0001 Fax 716 685 3886 For Additional Specification Information Visit www pcb com 162 Technical Information Strain Introduction ICP quartz strain sensors incorporate a built in MOSFET microelectronic amplifier This serves to convert the high impedance charge output into a low impedance voltage signal for analysis or recording ICP quartz strain sensors powered from a separate constant current source operate over long ordinary coaxial or ribbon cable without signal degradation The low impedance voltage signal is not affected by triboelectric cable noise or environmental contaminants Power to operate ICP sensors is generally in the form of a low cost 24 27 VDC 2 20 mA constant current supply Figure 44 schematically illustrates a typical ICP strain sensor system PCB offers a number of AC or battery powered single or multi channel power signal conditioners with or without gain capabilities for use with strain sensors In addition many data acquisition systems now incorporate constant current power for directly powering ICP sensors Because static calibration or quasi static short term response lasting up to a few seconds is often required PCB manufactures signal conditioners that provide DC coupling ICP quartz strain sensors are well suited for continuous unattended strain monitoring in harsh factory environments Also ICP sensor cost per channel is substantially lower since they operate through standard low cost coaxial cable and do not require expensive charge amplifiers Refer to the installation outline drawing and specification for details and dimensions of the particular sensor model number s purchased Description 240 series quartz strain sensors are used to monitor the dynamic response of crimping stamping punching forming and any other applications where it is crucial to maintain process control These sensors are ideal in applications where mounting directly in the load path with a force sensor is not possible Instead the sensor can be mounted in an area that will provide the highest mechanical stress for the process to be monitored Strain sensors are mounted to a structure by means of a supplied socket flat head screw which threads into a corresponding tapped hole and is then fastened securely When used with a constant current signal conditioner the sensor output voltage can be resolved in units of strain and then related to specific events that must be monitored in the process After defining a signature voltage response for properly manufactured parts the user can then determine an acceptable upper and lower control limit in order to maintain process control thereby preventing the acceptance of non conforming products as finished goods Versions offering full scale measurements of 10 µε to 300µε are available When powered by a constant current power supply and subjected to an input strain an ICP strain sensor will provide a corresponding output voltage A positive output voltage indicates that the structure being monitored is being subjected to a tensile force in the sensor mounting area and can also be resolved in units of strain Likewise a compressive force in this area will result in a negative output voltage Figure 44 ICP Sensor System Schematic Readout Device not supplied Output Cable ICP Sensor Signal Conditioner Standard Sensor Cable ICP Strain Sensor Typical ICP Strain Sensor Measurement System B Standard Sensor Cable or Output Cable I ICP Strain Sensor Readout Device with Built in ICP Sensor Excitation not supplied Standard Sensor Cable or Out t Cable ICP Strain Sensor ICP Sensor Signal Conditioner Output Cable Readout Device not supplied Low noise cables are required to maintain conformance Figure 45 Standard Sensor Cable 9 T Mcatalog 2011 Seite 125 166 SYN G500 21 04 11 18 04 Seite 168


Vorschau PCB Test & Measurement Seite 164