ICP/IEPE Excitation voltage and IOTech 650U

[rajoria]

Hello all,

I am using IOTech 650U DAQ (NI product no. 781277-01) with ICP/IEPE accelerometer. It works fine with PCB/IMI general purpose accelerometers (example model IMI 607A11). We want to use seismic accelerometers and are wondering if IOtech 650U can collect data from seismic sensors (example model - IMI 626A04). Most electrical specs of the two sensors are similar (2-20 mA constant current) except that the excitation voltage is more for seismic sensor (24-28 VDC) than general purpose (18-28 VDC). What does this mean and does it mean IOTech 650U cannot work with seismic sensor? I don't think so, but I am not sure. I tried to read about it and found NI article about excitation voltage to be less than compliance voltage (http://digital.ni.com/public.nsf/allkb/3CEFD95B14604C7386257598006C6233).
However, I could not find the compliance voltage spec of IOTech 650U. Any help regarding this is very much appreciated. I am looking to know if we can use seismic accelerometer (IMI 626A04) with IOTech 650U or not? Thanks.

[Henrik_Volkers · Accepted solution]

Usually you want to measure low or very low frequencies with seismic sensors.

So check if the high pass frequency of your DAQ matches your needs.

A lower max supply voltage will only limit the max amplitude can measure... 

[rajoria]

My DAQ has 0.1 Hz high pass filter for AC coupling. So, I guess that's the least I can go for seismic measurements. Generally  voltage levels are not significant for low seismic measurements and so for this reason we tend to use higher sensitivity sensors (there are upto 10 V/g seismic sensors). It's good to know that a lower max supply voltage only limits the max amplitude that can be measured. Thanks.