초록 ▼

A level sensor for sensing the level of viscous, electrically conducting materials in a tank includes a variable capacitor, the capacitance of which varies in response to changing material level height in the tank. The variable capacitance is connected through a charging resistor to a comparator to

A level sensor for sensing the level of viscous, electrically conducting materials in a tank includes a variable capacitor, the capacitance of which varies in response to changing material level height in the tank. The variable capacitance is connected through a charging resistor to a comparator to form an astable multivibrator which develops an output signal having a period dependent partly upon the capacitance of the variable capacitor. The charging resistor has a resistance which is small with respect to the resistance of the material so that build up or coating of material on the variable capacitor has little or no effect on the measurements. The frequency of the output signal from the multivibrator is divided to derive a signal of relatively low frequency which may be coupled to a remote location by a two wire conductor.

대표청구항 ▼

A level sensor for developing an output signal indicative of the level of a viscous electrically conductive material in a tank, the material having an electrical impedance including a resistive component, comprising: a variable capacitor having first and second electrodes, the capacitance between th

A level sensor for developing an output signal indicative of the level of a viscous electrically conductive material in a tank, the material having an electrical impedance including a resistive component, comprising: a variable capacitor having first and second electrodes, the capacitance between the electrodes being a function of material level height in the tank; a charging resistor coupled to the variable capacitor having a resistance which is selected to be substantially less than the resistive component of the material between the first and second electrodes; and an oscillator which includes the charging resistor and the variable capacitor for developing an output signal having a period which is dependent upon the resistive component of the material between the first and second electrodes, the resistance of the charging resistor and the capacitance of the variable capacitor so that the output signal period is substantially independent of build up of material on the variable capacitor.