Level measurement and control

Claim 3

An arrangement for performing the method according to claim 1, characterized by a detector adapted to be immersed in said fluid or substance, said detector including at least two electrodes insulated from said fluid or substance, a high-frequency voltage supply, and a load resistor, one of said electrodes being connected to one terminal of said high-frequency voltage supply and the other of said electrodes being connected to one terminal of said load resistor, the other terminal of said load resistor being connected to the other terminal of said high-frequency voltage supply.

Claim 6

An arrangement for performing the method according to claim 3, characterized by a suction or delivery nozzle connected to said pump and including at least one set of embedded fully covered electrodes, said nozzle being adapted to be immersed in said fluid or substance, a high-frequency voltage supply, said electrodes being coupled to said high-frequency voltage supply so as to achieve a voltage proportional to the resistance present between said electrodes and means for controlling said pump in response to said voltage so that a predetermined level of said fluid or substance is maintained.

Claim 7

An arrangement according to claim 4 including a synchronous detector for multiplying the measuring voltage by the voltage measured, a proportional controller connected to the output of said synchronous detector for setting a desired level, said controller being adapted to produce a controlled output voltage, a differentiator adapted to produce a differentiated voltage of said controlled output voltage, a first multiplier for forming the product of said differentiated voltage and a pump control voltage, a low-pass filter adapted to produce a first voltage and having its input connected to the output of said first multiplier, a second multiplier for multiplying said differentiated voltage by itself, a second low-pass filter having its input connected to said second mulitiplier and adapted to produce an output voltage, a divider for forming the quotient of the output voltages of said first low-pass filter and said second low-pass filter, and a third multiplier for forming the product of said quotient and said controlled output voltage.

Claim 8

An arrangement according to claim 4 including an accelleration limiter for limiting the over- or underpressure in said nozzle as caused by pump action.

Claim 9

An arrangement according to any one of claims 4, including two transformers, said electrodes being floatingly connected between said two transformers.

Claim 10

An arrangement according to claim 4, including a light emitting diode and a light-sensitive transistor, said pump control voltage serving for pump control being applied to said pump by means of said light emitting diode and said light-sensitive transistor.

Claim 11

A method according to claim 3 wherein said nozzle includes at least one set of fully embedded and fully covered electrodes peripherally spaced along the wall enclosing a central aperture, said nozzle further including lead wires for said electrodes.

Claim 12

A method according to claim 3 for eliminating the infuence of the surface area of said fluid or substance, differentiating an output voltage produced by said controller, multiplying to a proportional controller by means of which a desired level can be set said differentiated voltage by a pump control voltage to be used for pump control, passing the product voltage through a low-pass filter to produce a first voltage, dividing said product voltage by the product of the differential voltage multiplied by itself said second product voltage through a low-pass filter to produce a second voltage, multiplying the output voltage by a quotient voltage so as to form the pump control voltage for controlling the pump.