Hi, we bought ADXL335 and ADXL377 Accelerometers for our lab. The typical sensitivity is 6.5 mV/g for ADXL 377, and it is 300 mV/g for ADXL335 when the power is 3 V at 25 C based on the Data Sheet. If we use different power such as 3.3 V, how can do the calibration to get the sensitivity? If the temperature changes 30 C, the sensitivity change will be 0.6%, right? During the calibration, when we put the sensor still, we can get the reading for 0 g, right?
Thanks for your question. Each ADXL335/ADXL377 has it's own sensitivity, even under 3.0V, you can see the specified min and max on the spec table. If you want to get the accurate sensitivity for each sensor under different supply voltage, you may want to conduct a calibration(e.g. two points calibration) with a reference instrument for each sensor. If you don't want to do this, you can roughly calculate the typical sensitivity value. For example, the ADXL335 output is ratiometric, so the output sensitivity varies proportionally to the supply voltage. If Vs= 3.3V, then the typical sensitivity is 300mV/g * 3.3V/3V = 330mV/g.
If the temperature changes 30C, the sensitivity change will be +/- 0.6% for ADXL377 and +/- 0.3% for ADXL335.
When you place the sensor still(on the surface of the earth) and facing upwards, then you have 0g field for X and Y Axis, and 1g filed for Z axis.
Hope this helps.
Thanks a lot! It helps to confirm our procedures.
One more questions, if we use two points calibration to get values at -1 g and 1 g for ADXL377 which is the easiest way to do the calibration. But the range of ADXL377 is from -200 to 200 g. -1 to 1 g is only 0.5% of the total measuring range. Does the ADXL377 have a good linearity in this wide range?
For the two points calibration, we usually do one at the low end of the measurement range and the other one near the high end of the measurement range. So doing calibration under +/- 1g for ADXL377(200g part) will introduce a lot inaccuracy.
If we want to do a calibration(e.g. two points calibration) with a reference instrument for each sensor. What kind of instrument we can use? Other calibrated accelerometer or you have other good suggestion? Thanks.