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Scheme of the buoy level meter with an electric power converter:

1 — buoy; 2 — lever; 3 — cargo; 4 – dividing membrane
The buoy 1 is suspended at the end of the lever 2, at the other end of which there is a load 3 balancing the weight of the buoy 1 at zero level (another method of weight compensation is also possible). The separation membrane 4 serves to seal the tank.?
When the level changes, the force with which the buoy acts on the lever changes. The imbalance of forces leads to the displacement of the lever and core of the differential-transformer converter, which serves as an indicator of IR mismatch. Its output signal is sent to amplifier U, the output current signal of which is received by the output of the device and the feedback device of the UOS.
The latter is an electropower converter that develops a force that eliminates the imbalance of forces.
Level gauges of UB are designed to measure the level of non-viscous and viscous, non-precipitating, non-crystallizing media at pressure - (4 ... 16) MPa and temperatures from -200 to 200 ° C, medium density (600 ... 2500) kg / m3. The upper limits of the measurements are selected from the range from 0.02 to 16 m, the basic error ±1; 1,5%. In the level measures for chemical industries with a pneumatic output signal of the UBK-1 and DBU-1 types, another type of output from the buoy is used - with the help of a torsion tube, to the output of which the pneumatic transducer flap is attached. DBU-1 level gauges are used on media with a temperature of 5...230 ° C at a pressure of up to 2.5 MPa and a density of 700... 1410 kg/m3. The upper limit of measurement (0.4...6) m, the main error ±2.5%.