calibration MMA7361L Accelerometer

[aadil93]

Hello,

Does anyone now how to calibrate a MMA7361L accelerometer on labview?

Any help would be much appreciated.

Kind regards,,

Aadil

[Henrik_Volkers]

Static: turn it in each 6 positions , measure the output voltages , do some math ...  look up your local  g  (some say one turn per axis (=3positions) are enough ....)

Dynamicly: place it on a shaker together with a reference , excite the sensor, measure .....

there is at least one appnote from AD or Freescale on earth gravity cal. ....

If you do this ON a LabVIEW DVD one migth say that you have done it on LabVIEW 😉  

Oh it's friday 😄

[eseller]

Hello Aadil,

I'm not very familiar with the LabView aspect, but can help with the measurement technique.

For a static measurement, turning it in the 6 positions as suggested by Henrik is a good method. Gravity is a physical constant (with some variation based on location) and will give you traceability directly to the SI.

When performing a static measurement, we generally like to use gravity to apply a +1 g and -1 g to the axis being tested (sensitivity is the difference in output at these two positions divided by 2). The 0 g orientation is generally avoided unless there is some practical limitation requiring us to use it (like the cable/connector being in the way).

Why? Because the true input applied to the sensing element is far less sensitive to errors in the orientation of the sensor in the +1 and -1 g orientations compared with the 0 g direction (cos(0 +/- x) vs. sin(0 +/- x); where x is the position error; for small values of x, the difference in the "cos" value is close to 0 whereas the difference in the "sin" value will be almost equal to x).

If you are using the sensor dynamically, calibration gets a little more complicated. ISO 16063 Part 21 covers the method, but you will essentially be learning dynamic calibration, shaker control (which can damage the shaker if done improperly), and a far more complicated uncertainty analysis (at least if you want to do it right). Narrow-band measurement techniques such as DFT or FFT are also recommended.

If you do not already have this knowledge base, you may want to consider contacting a local metrology lab (if you have a small number of units) or consider a commercial calibration system (if you have a larger number of units). We do both of these and are happy to work with you if you decide that dynamic calibration is needed.

Eric Seller

Application Specialist

The Modal Shop, Inc.