Resistive electromagnetic gauges supply a continuous linear output signal which, using a suitable instrument, can indicate the level of liquid inside the tank. The gauge contains a set of reed switches; the pitch (the distance between switches) is 10 or 20 mm, and each reed switch is connected to a resistor.
The magnet on the fl oat closes the reed switches inside the stem one by one and is connected to a known point of the chain of resistors (see fi gures 9 and 10).

The gauge’s output resistance (Rtot) is obtained from the formula:



The Rtot value may increase (link C-A) or decrease (C-B) as the level increases.
Complete insulation of the contacts means that these gauges can also be used in conductive fl uids.
The Rp value is calculated by our engineers on the basis of the customer’s specifi cation and the length of the sensor.

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