Checking Accelerometer Offset After Final Board Mounting

An accelerometer can show a different offset after the board is fastened into its enclosure than it did during bare-board testing. The sensor is a mechanical structure, and the assembly around it can affect its behavior. For precision tilt or motion applications, establish the final mounting condition before deciding whether calibration is complete.

Connect the test to the package guidance

The Analog Devices ADXL314 data sheet identifies soldering, board mounting stress, and compounds applied around the device as potential contributors to offset changes. It recommends performing any needed offset compensation after system assembly. Apply the selected sensor’s own guidance rather than assuming every package responds identically.

Record the board support locations, fastening sequence, enclosure revision, and any coating or potting near the sensor. Include the condition of attached cables if they can load the board. A measurement made while the PCB is held loosely by hand is not equivalent to one made in its intended fixture.

Make comparisons with controlled orientation

1. Define the sensor axes relative to the product reference frame.
2. Measure in repeatable, known orientations using a suitable fixture.
3. Record temperature and allow a defined stabilization period.
4. Compare before and after each significant mechanical assembly step.
5. Repeat selected measurements after disassembly and reassembly where appropriate.

A changed reading can result from actual orientation change as well as offset. If tightening the enclosure tilts the board, the sensor may correctly report a different gravity projection. The fixture and analysis must distinguish that geometric change from an electrical or mechanical bias shift.

Resolve the source before calibrating it away

For example, a repeatable change associated with one fastening step suggests examining local support and board deformation. A variable change between assemblies suggests that the mounting process itself may need better control. Applying a fixed software correction to an uncontrolled mechanical condition can leave large unit-to-unit differences.

Calibration does not replace checks for vibration response, dynamic range, bandwidth, or temperature behavior. Keep those performance questions separate. The device’s self-test also has a defined purpose and should not be treated as proof that the complete mounted system has the required offset accuracy.

Release a controlled mechanical assembly and a calibration stage that represents it. Store calibration records with unit identity and relevant configuration. If a later change adds a stiffener, changes a fastener, or introduces material around the package, repeat the comparison. This keeps compensation tied to demonstrated system behavior rather than to an earlier, mechanically different version of the board.