• Active Controls

Continuous Level Transducer

Active Controls offers a Continuous Level Transducer, which is used for a wide variety of industrial level indicating applications. A reed chain and travelling float design allows the system to function independently of liquid electrical properties, temperature, pressure, foaming or the presence of vapours. A selection of materials ranging from stainless steel, to plastic, to Teflon, provides compatibility with a large variety of process liquids. Typical applications include waste water and sewage treatment plants, charging and mixing bins, containers for chemicals, beverages or vegetable oils, remote level indication for rivers or reservoirs. High reliability is assured by keeping the moving part count down to a single, non-friction component (the float). Function: the transducer consists of a guide tube onto which a float is inserted. A magnet inside the float actuates a series of reed switches inside the tube. One contact of the reed switches is connected to a resistance chain every 10 mm, and the other contact to a common terminal. The entire system functions as a potentiometer whose resistance is determined by the location of the float on the guide tube. An external electronic controller uses this variable resistance and converts the resistance to an analog signal (0/4–20 mA, voltage), or presents the level information on a display. An integral 4-20 mA transmitter can be added to some versions as an option. The accuracy of the system is a function of the reed switch spacing. This spacing varies from 10 mm (0.4 inches) to 20 mm (0.8 inches) depending on transducer model and overall length. The magnet closes either one or two switches at all times. Interpolation allows accuracies of 1/2 the switch spacing. Brief specifications: output signal – 4-20 mA, 0-10 V, 0-5 V; power supply 220 V AC; resolution – 10 mm for tanks up to 2 metres, 20 mm (for tank depth > 2 metre); transmission housing – SS; and max temperature – 120°C.