PRINCIPAL OF SERVO MEASUREMENT
14 Service Manual Part No.: 4417340 Revision 1
954 SmartServo FlexLine
3.2 Servo gauges
Servo tank gauges (Figure 3-2) are a considerable improvement over
the float driven instruments. They were developed during the1950s.
In this gauge, the float is replaced by a small displacer, suspended by a
strong, flexible measuring wire. Instead of a spring-motor, servo gauges
use an electrical servo motor to raise and lower the displacer. An
ingenious weighing system continuously measures the weight and
buoyancy of the displacer and controls the servo system.
The motor also drives the integral transmitter. Mechanical friction in the
servo system, transmitter, local indicator and alarm switches has no
effect on the sensitivity and accuracy of the gauge. Also, turbulence has
no direct effect. An integrator in the serve control system eliminates the
effects of sudden product movements. The gauge not only produces an
average level measurement under turbulent conditions, but it also
eliminates unnecessary movements and reduces wear and tear, greatly
extending the operational life of the instrument.
Figure 3-2 Servo gauge
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