TLDR: Can a 9205, 9202, or similar DAQ be successful and useful at measuring DC MEMS accelerometers? Why/why not? What is the recommended set up?
Scenario: need an accelerometer and DAQ system to measure +/- 2g at 0-~600 Hz, the 0Hz being the important spec. NI has out of the box piezoelectric accelerometer DAQ solutions, but MEMs doesn't appear to have an NI turn key. I am fine adding in my own power supply excitation so the module doesn't need to provide that.
So we're left with what DAQ to choose, since DC MEMs and external excitation rules out IEPE.
Both are single ended
|Sensor||Type||Range (g)||sensitivity (V/g)||exc. current||exc voltage||Range FS|
|7533A1||DC Mems||2||0.42||350 uA||4 to 28||0.84|
|4030||DC Mems||2||1||4 mA||5 to 30||2|
Back in the day, you'd just go with a DSA/sound and vibration DAQ. But is that valid for DC MEMS since these DAQ modules favor IEPE and simultaneous sampling?
I'm inclined to go with a 9202 w/ external excitation. Why? Channel count, cost, and resolution. Will this work?
|DAQ model||Cost||Sampling||Channels||Sample Rate||Low||High||bits||range||V/bit||7533A1||4030||Cost/channel||Note|
|9234||$ 2,553.00||Simultaneous||4||51.2k||-5||5||24||10||596.0E-9||1.4E-6||596.0E-9||$ 638.25|
|9239||$ 1,538.00||Simultaneous||4||50k||-10||10||24||20||1.2E-6||2.8E-6||1.2E-6||$ 384.50|
|9202||$ 1,795.00||Multiplexed||16||10k||-10||10||24||20||1.2E-6||2.8E-6||1.2E-6||$ 112.19||Top contender|
|9230||$ 755.00||Simultaneous||3||12.8k||-30||30||24||60||3.6E-6||8.5E-6||3.6E-6||$ 251.67|
|9229||$ 2,048.00||Simultaneous||4||50k||-60||60||24||120||7.2E-6||17.0E-6||7.2E-6||$ 512.00|
|9205||$ 1,152.00||Multiplexed||32||250k||-1||1||16||2||30.5E-6||72.7E-6||N/A||$ 36.00||Outside the DC offset bias|
|9215||$ 772.00||Simultaneous||4||100k||-10||10||16||20||305.2E-6||726.6E-6||305.2E-6||$ 193.00|
|9205||$ 1,152.00||Multiplexed||32||250k||-10||10||16||20||305.2E-6||726.6E-6||305.2E-6||$ 36.00|
I'll loop back to this once I get something working since I've seen a bunch of other forum posts that ask this but haven't closed loop.
First of all, kudos for providing a good level of detail and sharing your exploration so far. Such detailed posts are hard to find in the forum.
Based on your requirements (0 Hz & external excitation), I would also agree that 9202 seems prospective. I will try to spend some time to check for any argument why not 9202 for your application.
The natural selection of DSA cards is for their excellent frequency retention and large dynamic range. 9202 provides a similarly wide dynamic range but is limited in input voltage ranges.
If you look at the MEMS noise spec all bits beyond 13 (or less) are noise (consider full range) so 16 bit is OK
The output impedance of the MEMS is not specified , if you don't need simultanious sampling the multiplexed DAQ channels look cheap, but have a look at settletime error in the spec (prone to channel crosstalk). I always try to avoid muxed inputs.
The DC offset is sligthly different between units.. if DC is of concern .. so you will need an individual calibration (always recommended and easy done with a good estination of g_local)
If you need a connector / supply board anyway, you can add one OP per channel that remove the offset and add gain if needed (see noise 😉 ) , again a calibration in earth gravity for each channel ...
@santo_13: If you offer kudos .. there is a button to really provide them 😄
Thanks Henrik for the thoughts!
We've selected the 7533AX accelerometers family which have an output impedance of 100Ohm. Sampling rate would be anywhere from 1.2kHz to 6kHz. I will look out for this when I begin experiments.
I'm not certain adding in additional circuitry to the front end is necessary for this application. While maximizing the dynamic range is always nice, upon discussion with our engineer partners, we're well within the resolution of interest.