High precision inclinometers are vital to providing feedback on the tilt of a plethora of applications. However, what happens when it is placed in an environment that includes linear motion? Many applications will put some acceleration on an inclinometer such as rail maintenance of way, pavement profiling, and robotics. When this happens, you need to know what to expect to see from your readings.
When Acceleration is Applied....
Forced balance inclinometers are gravity-referenced, which means they are constantly undergoing gravitational acceleration, even at rest. When the sensor is tilted by an angle ?, this is recognized as an acceleration component T, where T = Gsin? (see diagram). For small angles measured in radians, sin ? = ? and this can be shown as T = ?.
If the sensor receives a horizontal acceleration of magnitude T, it will respond the same whether that motion is tilt or acceleration. An acceleration of one milliG is the same as a tilt of one milliradian and both are measured with the same amplitude within the passband.
How to Differentiate Acceleration from Tilt
When both acceleration and tilt are present in your application, there are a few methods to differentiate one from the other. If the tilt is being read at a lower frequency than acceleration, the acceleration can be removed by low-pass filtering. Many Jewell analog inclinometers can be customized with a low-pass filter.
You may also want to perform an analysis to determine if the acceleration amplitudes are much lower than the tilt. If so, you may be able to safely ignore the acceleration, even if both occur at the same frequencies.