Why Calibrate Accelerometers?

Aug 11

Accelerometer Calibration Intervals

Our first response to the question about accelerometer calibration and intervals is to consider what is the cost of failure. If you make a measurement and you later find out the sensor (or measurement channel) was bad, what would be the cost of invalidating that data or retaking it (if even possible)? The costs could vary from nothing to immense.

For example, if the test is a simple learning experiment in a university measurements course and taking retaking the data would cost nothing, then there is no harm. In fact, many professors design measurement courses and instructions assuming that students will make mistakes. Learning from mistakes does a wonderful job of deepening our understanding and reinforcing proper techniques.

Typically, the costs of a bad measurement are low when it is part of a large modal survey or single channel in a test. These units of measurement often occur with automotive structures where only 10’s million would be lost if not inspected for another day but can become costly for prototypes and aerospace structures.

A more extreme category of measurements includes ones that happen only once, and usually involve telemetry. For example, rocket launches and building implosions are in this category, where telemetry is involved. This type of measurement often needs to be correct; channels are checked multiple times and data is backed up. You name it and double-checking a measurement plan is likely a part of it.

The design of a measurement microphone differs from a communications microphone, which is designed to always produce an intelligible output regardless of the environment. Along with calibration, measurement microphones are subject to type certification in order to maintain accuracy.

Regardless of your "cost" of failure, some aspects will always be the same. For example, you need to rely on credible (ISO 17025 accredited), high-quality calibration for your lab in order to create accurate results. Some companies choose to build these capabilities in-house, while others outsource to other companies or vendors. Whichever you choose, be sure that you know, trust and audit the expertise of those that provide calibration services for your lab.

We’ve often heard the advice to live your life like your choices will be published in the headlines of tomorrow's news. Sometimes making a good choice takes courage and sometimes it is about making any choice at all…

Are you calibrating accelerometers regularly?