IIS3DHHC Factory Calibration Details

JZhan.4 · ‎2020-03-26

Hi,

I would like to know what factory calibration procedure has been performed on this sensor and how are the calibration values used behind the scene? More specifically, there is a temperature compensation enable bit in the register map; I would like to know how it's being used and what would be the final temperature coefficient on offset with this temperature compensation used. On the datasheet, it's listed at 0.4mg/C. Is this before temp compensation or after?

Another related question is on the "excellent stability over time" that's advertised on the first page of the datasheet. I could not find more details or specification on the stability. Can you provide more information from your characterization?

Thanks,

John

Eleon BORLINI · ‎2020-03-27

Hi @Community member , I try to answer to your question here below

>> what factory calibration procedure has been performed on this sensor and how are the calibration values used behind the scene?

the factory calibration procedure typically includes a series of steps involving EWS calibration of electrical parameters and Inline tester calibration on mechanical parameters (sensitivity). Temperature calibration is performed at Inline tester level too.

>> On the datasheet, it's listed at 0.4mg/C. Is this before temp compensation or after?

The embedded temperature sensor is calibrated to get a zero offset at 25°C, while the accuracy of the temperature sensor is inside +-15°C across the temperature range -40°C to 85°C. The accelerometer sensitivity change vs. temperature average value after compensation is 0.7%.

>> Can you provide more information from your characterization?

I can share you the characterization data on a limited sampling about the sensor stability vs time (hours) and temperature (deg):

Regards

JZhan.4 · ‎2020-03-30

Hi @Eleon BORLINI , thank you very much for your answers. I would like to ask for a few clarifications.

For a tilt sensing application, I'm more concerned with temperature effect on the offset (not sensitivity which you discussed earlier). In the datasheet, it's listed as 0.4mg/C after the temperature compensation bit is enabled. I'm wondering what kind of temperature compensation is done here. For example, you measure offset at two temperatures and then derive an offset value to use in internal compensation. Can you provide a plot of the unit's typical offset vs temperature? The motivation is that if the curve is linear, then we can do simple additional calibrations to make the sensor more robust across temperature.
Does ST offset this inclinometer application intended accelerometers in higher temperature packages? (e.g. -40 to 105C)
How should I obtain your characterization data on sensor stability vs time and temperature?

Thanks a lot,

John

Eleon BORLINI · ‎2020-03-31

Hi John, I try to answer to your question here below.

Can you provide a plot of the unit's typical offset vs temperature?

You can find a plot of the X axis here below, from characterization data. Similar plot for the other two axis. the drift is inside +-0.2mg/°C

2. Does ST offset this inclinometer application intended accelerometers in higher temperature packages?

The only package available for this accelerometer is the ceramic cavity LGA-16 (5x5x1.7 mm). However if you can accept a degradation of the performances, the device can survive up to 105°C and more.

3. How should I obtain your characterization data on sensor stability vs time and temperature?

Raw data are not available for the sharing. You can refer to the previously attached image or you can directly test a device...

Regards