Accelerometers (App Note)

This application note is about selecting and using accelerometers and vibration sensors.

Power Supply:  The ideal sensor runs off 5 volts DC so you can power it from any LabJack, but if a sensor needs 12 or 24 volts DC that is easy to provide with an external power supply.

Signal:  The ideal signal is a voltage signal that matches the analog input range of the LabJack.  With the ±10 volt inputs found on most LabJacks, the typical signal ranges of 0.5-4.5, 0-5, 0-10, or ±10 volts are all excellent options.

MEMs

These are usually the best option.  MEMS sensors often have the ideal characteristics of accepting a 5 volt power supply and providing an easy-to-use voltage output signal such as 0-5 volts.  LabJack has used some MEMS sensors like this from Analog Devices and Measurement Specialties (now part of TE) among others.  Digikey is a source for Analog Devices and other brands. 

Raw Bridge

If the output is specified as something like 2 mV/V, that is a raw bridge sensor.  Another thing to look for is 4 wires labeled something like Excitation+, Excitation-, Signal+ and Signal-.  A raw bridge sensor can be handled, but is certainly more demanding than a signal-conditioned sensor.  For more information, see our Bridge Circuit App Note.

ICP or IEPE

One common type of accelerometer is the ICP or IEPE type.  This provide a decent high level voltage signal, but the problem with these is they need a special constant current excitation source typically providing 2 mA to 10 mA at 18-30V.  We do not provide such an excitation source so that will have to be sourced along with the sensor. 

ICP/IEPE signals can often be measured directly, but sometimes you need to AC-couple to get rid of DC offset. You might also need the LJTick-InBuff to buffer the signal.

It is suggested that if using an ICP or IEPE sensor a signal conditioner also be acquired to go with it.  Look for a signal conditioner that provides the special current source excitation and also conditions the output signal if needed.