Inertial Sensor Technology

How Servo Inclinometers work

The Sherborne Sensors' range of servo inclinometers are extremely sensitive transducers measuring horizontal and vertical inclination with virtually infinite resolution using a 'taut band' detection mechanism.

Ranges ±1° to ±90°
1500g mechanical shock
DC input - DC output
Output proportional to sine of tilt angle
Resolution down to 0.1 arc second

Typical applications include road grading, borehole alignment, satellite dish alignment, tilt train control and other applications where high accuracy of tilt measurement is required.

All units are manufactured under ISO 9001 conditions.

All inclinometers operate as a closed loop torque balance servo system (see figure below).

The heart of this gravity referenced angle detector is a torsional flexure supported moving mass system that is rugged enough to withstand severe shock and vibrations and still maintain excellent precision and accuracy. The servo system electronics, torque motor and feed?back sensor are all enclosed within an environmentally sealed housing permitting operation under hostile conditions without degrading performance.

As the inclinometer is tilted through some angle (ø) along its sensitive axis, mass 'A' tries to move in the direction of tilt as a result of a force (torque) applied to the mass by the normal component of gravitation acceleration.

The resulting change in position of mass 'A' is detected by position sensor 'B', which produces an error signal output. This DC error signal is fed to a servo amplifier whose output is a DC current coupled to the armature of torque motor 'C' through 'Ro'. Current applied to the torque motor armature produces a torque that opposes the gravitational force acting on mass 'A' and moves it back towards its original position.

The current passing through 'Ro' generates a voltage across 'Ro' that is proportional to the normal component of the gravity vector. The normal component is the product of the essentially constant gravity vector times the sine of angle ø. Therefore, the output voltage across 'Ro' is proportional to the sine of the tilt angle ø.

This information has been kindly supplied by:

Sherborne Sensors Ltd.
Telephone: +44(0)870 444 0728
Fax: +44(0)870 444 0728
Web Site:


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