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A device for the capacitive measurement of a level of filling having a measurement capacitor which dips into the fluids to be measured in accordance with the filling level thereof, and a unit for forming an electric value corresponding to the filling level and a unit for compensating for different d

A device for the capacitive measurement of a level of filling having a measurement capacitor which dips into the fluids to be measured in accordance with the filling level thereof, and a unit for forming an electric value corresponding to the filling level and a unit for compensating for different dielectric constants of fluids which comprise a compensation capacitor dipping into the fluid. A circuit forms an electric value corresponding to the filling level and compensates the different dielectric constants of the fluid such that only the imaginary part of the complex conductance of the measurement capacitor and of the compensation capacitor enters into the electric value, but not the real part thereof in each case.

대표청구항 ▼

In a device for the capacitive measurement of a level of filling of a fluid in a container having a measurement capacitor which extends into the fluid to be measured in accordance with the level of filling thereof, means for forming an electric value corresponding to the level of filling, and means

In a device for the capacitive measurement of a level of filling of a fluid in a container having a measurement capacitor which extends into the fluid to be measured in accordance with the level of filling thereof, means for forming an electric value corresponding to the level of filling, and means for compensating for different dielectric constants of the fluid which comprise a compensation capacitor positioned in the fluid, the improvement wherein a circuit comprises said means for forming an electric value corresponding to the level of filling and said means for compensating for different dielectric constants of the fluid such that only the imaginary part of the complex conductance of the measurement capacitor and of the compensation capacitor enters into said electric value exclusive of the real part thereof in each case, said means for compensating forms a value in accordance with the equation [Figure] in which: h is the height of the section of the measurement capacitor extending into the fluid; l is the total height of the measurement capacitor; CK is the capacitance of a first compensation capacitor in the fluid; CKO is the capacitance of a second compensation capacitor in air; CM is the capacitance of the measurement capacitor in the fluid; and CMO is the capacitance of the measurement capacitor in air; said circuit includes: formation means for the formation of output voltage proportional to the respective capacitances of said capacitors, said formation means comprises a source of sinusoidal voltage for feeding feed voltage to subcircuits, respectively, for each of said capacitors, said subcircuits comprising a measurement resistor connected in series with one of said capacitors, respectively, said formation means includes means for producing a phase-shifted sinusoidal voltage which is shifted 90 degrees with respect to the feed voltage, said subcircuits further comprising, respectively, for each of said capacitors means comprising an alternating voltage multiplier with low pass properties having a cut-off frequency less than twice the frequency of the feed voltage for multiplying the voltage drop on the corresponding said measurement resistor by the phase-shifted sinusoidal voltage and for filtering an alternating-voltage component out of the voltage formed as a product, so that an output voltage proportional to the capacitance of the corresponding one of said capacitors is present at the output of the alternating voltage multiplier with low pass properties.