# FAQ: Gyroscope Sensitivity/Scale Factor Evaluation

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Q:

Is there a simple way to test the sensitivity (scale factor) in the ADIS16485's gyroscope, using the IMU Evaluation software?

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A:

Yes!  The following exercise leverages techniques for observing gyroscope sensitivity (scale factor), which are described in this post (and links provided in this post). http://ez.analog.com/message/44891#44891

1. Start with establishing a known "turn angle." I have found that using a fixed object, as a stop, provides a simple way for turning a gyroscope around a "half-circle," or 180 degrees. The video example (provided near the end of this post) illustrates this process with an ADIS16485AMLZ, mounted to an EVAL-ADIS. In this example, the range of motion is limited by the edge of a seminar book, which is pressed up against a cubicle wall in an office. I like simple!

2. Start the IMU Evaluation software and use it to configure both IMU and the data capture process.  Here is a summary of the settings, which are critical for this exeriment and are reflected in the figures below.

• DEC_RATE = 0x003D, sets ADIS16485 sample rate to ~39.68 SPS (2460/62)
• NULL_CFG = 0x070A, sets the average record size to ~26.6 seconds.
• GLOB_CMD = 0x0001, executes an auto-null for the gyroscopes
• Total number of samples in the record = 500 samples (~12.5 seconds, total record time)
• Un-scaled data (no reason for this, other than personal preference)
• Select Z_GYRO, 32-bit register

3. Click on Start, then move the ADIS16485/EVAL-ADIS around 180 degrees, then back.  See the embedded video link for example of the motion used in this test.

4. See the attached Excel file for the data and calculations, but the angle computation is greatly simplified by the sychronous data capture in the EVAL-ADIS.  Simply divide each gyroscope data point by the sample rate, then add them all together to produce a real-time angle estimate. As we can see from the plot, the integrated result shows 180 degrees and angular displacement and the device returns to zero.

This FAQ was generated from the following discussion: A simple gyroscope scale factor test using IMU Evaluation