We are using ADXL312 in a new design, and have measured the output of the accelerometer:
MinX MaxX AvgX MinY MaxY AvgY MinZ MaxZ AvgZ
-50.00 58.00 -5.68 -54.00 48.00 -4.25 228.00 410.00 309.97
Minimum, maximum and average (mean) are calculated from 1000-samples.
The sensor is laying solid on my desk, so i expect to have about 1G at Z, and 0G at X and Y.
The accelerometer is configuration:
3200Hz data rate.
Watermark interrupt after 16 samples
As you can see, the output differences are very high, especially at the z-axis:
Min=228*2.9mG/LSB = 661mG
Max=410*2.9mG/LSB = 1189mG
avg=309.97*2.9mG/LSB = 899mG
I have already made some attempts to improve it, by changing decoupling of Vs, and to use a separate 3.3V supply for Vs. But it didn't help.
Have been looking into the data sheet which gives noise figures of 340uG/sqrt(Hz). My interpretation of how to use that number is:
noise = (3200/2)^(1/2) * 340*10^(-6) = 17.6mG.
Even if i would add bit truncation and other, types of error sources would i never reach the figures i experience.
My question is: What should i expect with these settings, how much noise should it be there if the implementation of the sensor was perfect?