Servo tank gauges are a considerable improvement over the float driven instruments. They were developed during the 1950s. In this servo 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.
Manual Gauging 8 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 servo gauge. Also, turbulence has no direct effect. An integrator in the serve control system eliminates the effects of sudden product movements.
The servo 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.The original servo gauge does not look much like today’s modern version. The instruments have evolved into highly reliable mature products, and are gradually replacing mechanical float gauges, cutting down on maintenance and improving on inventory results.
Modern intelligent servo gauges have very few moving parts, resulting in long term reliability and accuracy. They also have a high degree of data processing power. The instruments do not merely measure the liquid level but are also capable measuring interface levels and product density. Accurate, programmable level alarms are standard. Accuracy’s of better than 1 mm (1/16 inch) over a 40 m (125 ft) range can be attained. The exceptional accuracy and reliability has resulted in the acceptance of the measurements and remote transmission, by Weights & Measures and Customs & Excise authorities in many countries.
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