Constant z axis offset for -1g

Question

We use two ADXL355 on our custom board, one on top and the other one on the bottom. 
 In horizontal position, z axis of the top sensor gives +1g (as expected), while z axis of bottom sensor gives ~ -1.1g. 
 If we turn the board upside down, we get the same with switched roles. 
 Having an offset of >= 10% in the negative z axis was not what we expected, and we have never experienced this behavior before. 
 
 So my question is has anyone experienced similar constant, steady state offsets for nagtive z axis values?

MarioSM · Accepted Answer

Hello LoremIpsum thanks for posting. Does this same drift on the bottom sensor repeats sistematically on different boards? 75mg is rated as the max. limit for the offset on the 2g range, thus 99.7% of parts should present in worst case this offset on startup. Still, there are some other sources of error that can change the offset value as; non-simetrical PCB layout, a thermal gradient due to a power regulator routed nearby, presence of vias under the footprint or handling points further than 3cm are some of the factors that can help inducing tension in the sensor's package and translate in some extra 0g bias drift. On top of that, there is also place for variability from part to part on the sensitivity of the part, or non-mechanical factors as using an external supply instead of the internal LDOs can also lead to offset drift if it is not precise enough. Overall, for high precision applications calibration at least on room-temp is recommended after soldering the part. Remember that you can configure the offset trim registers for this purpose. Some collateral in relation to this topic: AN-1057: Using an Accelerometer for Inclination Sensing | Analog Devices (calibration guidance at the end) Choosing the Most Suitable MEMS Accelerometer for Your Application&mdash;Part 1 | Analog Devices hope this helps, have a great weekend. Mario SM)

SLA Status	Assignee	Support Status
SLA Closed. Met after 0 hours		Open

Popular Forums

Product Forums

Application Forums

Design Center Forums

Highlighted Webinar

Places

Libraries

Upcoming Learning & Events

Challenge Yourself!

What's Brewing

Places

Resources

Visit ContentZone

The Latest Read

New Release

Recent Technical Insights

SLA Information

Products Mentioned

Associated Drivers

Thread Details

Constant z axis offset for -1g

Thread Summary

Before You Switch