accelerometer static test 1

[janetdog]

hi guys,
i want to verify the operational characteristics of an accelerometer without using a shaker table can one test the integrity of a vib accelerometer by inputing a pulsed waveform and analysing the response signal? any info welcome.

 

[dgallagher]

Only "static" test I can think of is to check the sensors bias voltage. Observing the bias voltage is relatively easy and quick. Most industrial accelerometers available today are powered by +18 to 30 volts DC (typically +24 volts DC). This power is supplied on one of the two wires connected to the sensor. The accelerometer amplifier circuit inside the sensor pulls this power voltage down to a preset level. The preset level is called the bias voltage and is designed at a level by the sensor manufacturer. Most accelerometers have a nominal bias voltage half way between the power supply and ground(typically +12 volts DC). The sensor operates around this voltage level and the level should be relatively stable as long as the power level is stable. Bias voltage may be measured via a volt meter or collected as part of a route using a data collector.

For dynamic testing of the sensor - you need to shake, shake, shake...

 

[tomirvine]

Both Bruel & Kjaer (Model 4294) and PCB (Model 394C06) offer small battery powered shakers for checking the calibration of an accelerometer.

Tom Irvine

http://www.vibrationdata.com

 

[GregLocock]

Make a 1 kg steel cylinder. Mount the accelerometer on the centreline. Hold the cylinder in one hand and strike the other end of the cylinder with a calibrated load cell on a hammer. Perfect your technique until the measured FRF is flat for the frequency range of interest. Observe the magnitude of the FRF.

I use this as a quick check for the entire instrumentation chain when doing a modal analysis.

Probably not quite what the original poster had in mind!


Cheers

Greg Locock

 

[janetdog]

hi,guys i want to test a acelerometer which does not have a signal conditioning amp. its just a piezo crystal. i have seen that a pulsed do around 50 volts square wave then monitor for signal response is a method but need this scientifically verified.

 

[IRstuff]

It would seem to be A way to verify that the crystal itself is operational, but may not say much beyond that.

Presumably, the idea is that the voltage pulse stresses the crystal, and upon release of the input, the crystal relaxes and generates essentially a transient response equivalent to the effect of a step function shock input.

This is a quick & dirty check, but there's no means of verifying that the transfer characteristic of the housing and mounting haven't been perturbed.

TTFN

 

[janetdog]

thanks to all and IRstuff especially. i was wondering if it may be possible to include the crystal of the acelerometer in some sort of amplifier/oscillator which may allow it to produce a frequency output.has anybody ever did this before and would it work? i am trying to checkout a large number of accelerometers in situ without having to go through the cost of removing them and shaketesting them.any advice welcome.