Importance

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Abstract

The upwardly extending outlet of a pump contains a non-floating permanent magnet which tends to assume a lower end position but is propelled upwardly in response to admission of a metered quantity of liquid into the outlet to initiate the emission of a signal by a sensor. The emission of such signal persists as long as the actuator remains above its lower end position. The sensor is connected with the resetting input of a counter by way of an OR circuit. The n-th output of the counter transmits a signal to an alarm signal generating circuit in response to transmission of a certain number of consective timing pulses to its counting input prior to transmission of a signal to the resetting input. The timing pulses are transmitted by a generator which also transmits pulses to the pump to thus determine the frequency of admission of liquid into the outlet. A rectangular wave oscillator receives signals from the sensor and transmits a series of signals to the OR circuit with a delay which equals or approximates the length of the interval between two consecutive timing pulses. The oscillator starts to transmit signals to the OR circuit only if the signal which is emitted by the sensor persists during the aforementioned delay. This ensures that no alarm signal is generated if the viscosity of pumped liquid is so high that the actuator is incapable of returning to its lower end position during the interval between successive admissions of liquid into the outlet.

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First Claim