High Resolution Accelerometer DAQ

[AliasAlreadyOnFile]

Hello,

I intend to purchase a high sensitivity accelerometer in the next week and am looking for a new DAQ device to replace my NI USB-6008, whose resolution is far too low at (2V / 2^12) 0.0048V. I'm not entirely confident in my understanding of the main concepts behind this choice and would like confirmation (or otherwise) that I know what I'm talking about so that I don't waste £000's on something that doesn't do the job.

The new accelerometer has a resolution of 0.000004g but I only really need 0.00001g. With a sensitivity of 10 V/g, that equates to 0.0001V resolution required of the DAQ to match the resolution of the accelerometer. The unit I'm looking at is the NI-9239, which has a range of ±10V and 24-bit resolution. If I understand right that's (20 / 2^24) = 1.19E-6 V resolution. This easily matches the accelerometer.

Does this make sense or have I missed the point? I have a feeling somebody's going to say something about noise levels.

Anyway, I'm also planning on picking up a single-slot chassis for it with a USB connection. Later on, should I decide to add more accelerometers or impact hammers to the system, how easy is it to add to the system, e.g. buy another DAQ device and single-slot chassis and add this as an input to an existing VI. Do I just add it as another device using DAQmx and then worry about synchronisation or will I need further hardware?

Finally, what's the use in hardware filtering, e.g. high- and lowpass filtering, anti-aliasing filters etc, when I have all these implemented in my VI? Do I really need signal conditioning before my PC?

Thanks,

Phil

[Henrik_Volkers]

For absolute measurements :  12 bit should be fine 😉  (assuming a optimal range choosen)  

On the other hand, I just used a similar sensor (PCB, 10V/g, ICP) to do some enviromental vibration investigations

(Don't want to call it measurements)

Propper signal conditioning (and wirering) is important.  (I used a external ICP conditioner with 100x gain and a USB 6281 18bit in the 100mV range)
ICP is low impedance, however, I found a lot (line)  noise at this low level. (With sensor shortcut!)

If you have a specific task, ask your local NI sales ?repr.   to make a hands on test first.