What does it mean factory calibration for a accelerometer as LSM303 ?

[jtual]

Posted on March 14, 2018 at 09:22

Hello,

We used the LSM303D and now we use the LSM303AGR for a roll and pitch sensor (+/-45°C).

The LSM303 components are factory calibrated (cf. datasheet of the LSM303D, DocID023312 Rev 2) :

'The IC interface is factory calibrated. The trim values are stored inside the device in

nonvolatile memory. Anytime the device is turned on, the trimming parameters are

downloaded into the registers to be used during normal operation. This allows the user to

use the device without further calibration.'

Could you me give more details about it ?

For the LSM303AGR, there are more details :

'The IC interface is factory calibrated for sensitivity (LA_So, M_GN), Zero-g level (LA_TyOff) and Zero-gauss level (M_TyOff). The trim values are stored inside the device in nonvolatile memory. Anytime the device is turned on, the trim parameters are downloaded into the registers to be used during active operation. This allows using the device without further calibration.'

The specification of our roll and picth appplication must be have an +/- 0,5°accuracy in a +/-30° scale and an +/- 1° accuracy for +/- 45°.

With the LSM303AGR, do we need to do a calibration like indicated by the DT0053 Design tip ?

Thanks,

Jérôme.

[Miroslav BATEK]

Posted on March 16, 2018 at 10:15

The factory calibration basically means that each device in calibrated during production to reach its specification, which is listed in the datasheet.

Concerning the tilt measurement I would recommend you to read application note

http://www.st.com/content/ccc/resource/technical/document/application_note/d2/d6/22/4f/b9/8f/45/59/DM00119046.pdf/files/DM00119046.pdf/jcr:content/translations/en.DM00119046.pdf

.

If you check the datasheet for LSM303AGR you would find following information:

It means the device can have up to +/-80 mg offset so the error of tilt angle can be arcsin (0.08) = 4.59°

Your requirement for accuracy cannon be reached without calibration of each of your device.

Please be aware there could be other sources of inaccuracy like planarity of the soldered device, not precise placement of the PCB in your device enclosure, ...

[jtual]

Posted on March 19, 2018 at 14:50

Thanks, so, if I don't want to do a calibration phase, i need to use a component with +/-15 mg offset.

Jerome.