excitation current settings

[riccardoroberto.delucia]

Hi everyone. Firstly, let me apologise for my noob question. I am working with PCB 352a24 accelerometers and NI USB 4432 DAQ device. I need to setup the excitation current value in LabView, but I'm not sure which value to choose. The accelerometer specifications indicate a range from 2 to 20 mA. Now I need to choose a value in this range. I know there are common used excitation current values (e.g 2.1 mA) but I would like to know how to set it correctly. I searched for information all over the internet but with no results. What is the procedure to choose the correct value of excitation, given the device and the IEPE sensor? Thank you!

[Henrik_Volkers · Accepted solution]

If you want to use the 4432 without extra conditioner (constant current line driver) you don't have a choice and have to use the 2,1mA 😉

That's no problem, unless you use extremely long cables (the usual 3m cable can be claimed short :D) 

or need a high bandwidth (which you don't have since the sensor is specified up to 8-12 kHz)

A higher current lowers the output impedance of the sensor (that current has to drive the cable capacity), but increase the self heating of the sensor.  (assume 12V bias  @ 20mA -> 0.24W in a damn small sensor circuit)

So all is fine with that combination.

[riccardoroberto.delucia]

Hi Henrik! Sorry for my late reply to you! Thank you so much for the clarification. So the excitation current is a variable parameter which depends on several factors, and not only on the sensor itself. Indeed, in my configuration I use a short cable, therefore as you said 2.1 mA should be the correct value to set. I apologise again for answering you with such a delay, they have been quite busy days 🙂 

All the best,

Riccardo