Accelerometers

Other Hardware Sensors
1

Hello Arduino community,

So I am working on this project which employs MMA7361L accelerometer (1.5g / 6g), a GPS and an Arduino. Talking generally about how accelerometers work it all seems to be straightforward - the output voltage is proportional to the acceleration and these devices have associated sensitivity. For example, from the datasheet (http://www.farnell.com/datasheets/1714645.pdf) in 6g mode the sensitivity is noted as 206mV/g. My question is - why 206mV/g?

With 3.3V supply voltage, 1.65V output corresponds to 0g. Now isn't the theoretical 'sensitivity', which has units of mV/g, given by 1.65V / 6g = 0.275V?

2

why 206mV/g?

You'll have to ask the manufacturer.

Now isn't the theoretical 'sensitivity', which has units of mV/g, given by 1.65V / 6g = 0.275V?

No, the output is Vcc/2 for 0 g, plus a possible offset that you will need to determine, in order to properly calibrate the device. The excursions from Vcc/2 are dictated by the acceleration and sensitivity.

3

Offset, and one more things to account is output stage performance:

V FSO V SS +0.1 — V DD –0.1 V

Basically, output swing is not 1.65, but 1.55V