Question

I have two types of piezoelectric accelerometers: IEPE and straight charge type. I am new to using charge type accelerometers. I purchased an Endevco 133 signal conditioner some time ago to make vibration measurements with IEPE modal accelerometers. I am now required to make measurements in test locations with higher temperatures (500°F) and will be using charge type piezoelectric accelerometers. The 133 I described as a dual-mode signal conditioner. Can I use it with both accelerometer types?

Answer

Yes the 133 can be used with both IEPE and charge mode accelerometers. The caveat is that the 133 is a single-ended conditioner, designed for use with single-ended accelerometers. Piezoelectric charge mode accelerometers are available in single-ended and differential output. The 133 does not work with differential output accelerometers; they would require a differential signal conditioner.

""Dual mode"" refers to the ability of the conditioner to accommodate low impedance inputs (IEPE accelerometers, modal hammers or force transducers) and high impedance charge devices (accelerometer and pressure transducer), provided they are single-ended designs.

The 133 is configured using the EDIT pushbutton (up-down).

• For use with an IEPE sensor, you already determined that the ""select function"" pushbutton, set to IEPE, puts you in the correct mode.


• For use with an SEPE (single-ended piezoelectric) accelerometer, the same ""Select Function"" pushbutton should be selected for charge mode. The 10-32 miniature coaxial connectors, on low noise cable typically supplied with charge type accelerometers, are threaded to the individual channel charge input receptacle. It should be noted that each channel is independent where a mixture of SEPE and IEPE devices could be set up in a single 133 conditioner. The sensitivity input, full scale settings and filter options are the same as the IEPE accelerometer set up you have previously experienced.

Note the 133 can be configured in the constant current mode for connection with an IEPE sensor or a Remote Charge Converter (RCC). A charge accelerometer, therefore, can be connected to the 133 directly in through the 10-32 charge mode input or indirectly through the RCC into the BNC for constant current. See example block diagrams below for clarification.