This type of inclinometer is a precision inertial instrument (accelerometer) that responds to the normal component of the gravitational acceleration vector (gravity). Pendulous mass (A) is attached to the torsionally suspended armature of torque motor (C). Stops on either side of the mass (A) limit its travel when the device is not powered. When the power is applied, the pendulous mass (A) automatically moves to its zero position.
As the inclinometer is tilted through some angle (q) 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 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 the mass (A) and moves it back toward its original position. When the torque developed by the servo system output current just balances the torque developed by the gravity vector component acting on pendulous mass (A), the mass no longer moves and is at rest almost in its original position, being displaced by some minute amount that produces the required error signal from position sensor (B). Because the gravity components force is exactly equal in magnitude to the torque motors output, which, in turn, is directly proportional to the applied current, this current, passed 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 (q). Therefore, the output voltage, EO x across RO is proportional to the sine of the tilt angle q.
