How do pick a accelerometer?

[Atomize]

Hi, 

I am working on a robotic project. However it is vibrating a lot and causing the robot to hang. Thus I need to determine the maximum vibration frequency from the frequency response so that I can install a suitable vibration isolator.

In general, maximum mechanical vibration frequency is around 1.5kHz. So how do I choose what input range I need for the accelerometer? For example common ranges are +/-4g, +/-10g, +/-25g, etc. 

Awaiting your reply.

Thanks.

Regards. 

[Henrik_Volkers]

space?

mass?

budget?

MEMS accelerometer are cheap but most of them have a limited bandwith (300-600Hz).

Quick and dirty: hot glue a ECMic (canibalized headset) with the hole to the surface and use the soundcard with some freeware 

Other end: use the sound&vibration toolkit, purcase a modal hammer and the accelerometer/preamp . BTW: what type of DAQ are you using?

...

crystal ball: I would start with 10g.

[Atomize]

Hi Henrik,

Thanks for your quick and prompt reply.

As I am only looking for the maximum vibration frequency, I am not using any DAQ. I need a accelerometer which I can hook up to the digital oscilloscope. I will read of the frequency directly off the oscilloscope.

As I said the frequency of vibration that I need to measure is around 1,5kHz. So how do I pick the input range(in terms of gravity,g) for the accelerometer? I am looking for a moderate cost accelerometer.

Thanks. 

[Henrik_Volkers]

Quick coarse test for the range: place a small nut on a horizontal area. Does it lift off (Do you hear it?) ?  If no you are below 1g 🙂

Here are some cheap MEMS acelerometer with analog output and about 2kHz BW (if you don't mind to solder with a VERY small tip):  ADXL321  from Analog or LIS2L06AL from ST

If you are a student, ask for a sample!! 

[AEI_JR]

Atomize,

Accelerometers need signal conditioning, you cannot directly plug one directly into a scope.  If you use a charge type (PE) accel, you must use a charge amplifier, or a charge converter.  A charge converter will require a 2-20 mA, 8-20 VDC power source, as will an IEPE accel.  Piezoresistive accels require a DC voltage source.  Resource the PCB Piezoelectronics website (http://www.pcb.com/) for more information.  Since you don't know the level of vibration, I would actually suggest purchasing a higher range accel, perhaps 50-100 g limit, to be safe.