METHOD OF MEASURING ELECTRIC CAPACITY Russian patent published in 2018 - IPC G01R27/26 

FIELD: test and measurement equipment.

SUBSTANCE: invention relates to instrumentation and can be used in development of instruments, intended for measuring capacitance of capacitors and capacitor sensors of various process parameters (level, pressure, displacement, etc.). Method for measuring electrical capacitance C_X, based on recording time of charge t₁ of measured capacitor from the moment it is applied to it through resistor R of constant voltage E until it reaches measured capacitor C_X previously accepted threshold voltage value U₀, after connecting in parallel to measured capacitor C_X of reference capacitor C_O with known capacitance charge time of these capacitors t₂ is measured again, without changing resistance value R of resistor, charging source E voltage and previously received voltage threshold value U₀ on plates of these capacitors C_X and C_O. Using key K1 (Fig. 1) through resistor R at time t = 0 voltage E is applied to capacitor with measured capacitance C_X. Voltage U₁(t) on capacitor C_X, controlled by meter 1, begins to increase exponentially (Fig. 2), with time constant T₁. As soon as U₁(t) reaches pre-determined threshold value U₀, time t₁ is fixed. Constant voltage source E is switched off using key K1. Using key K3, capacitor with measurable capacitance C_X is discharged and sample capacitor with capacitance of C_O is connected to it in parallel using key K2 . With key K1, voltage E is again applied at time t = 0 to parallel capacitors C_X and C_O. Voltage U₂(t) on their plates begins to increase by more shallow exponent (Fig. 2), with time constant T₂. As soon as U₂(t) reaches pre-determined threshold value U₀, time t₂ is fixed. Measured capacitance is calculated by formula: , where C_O - capacitance of the sample capacitor; t₁ - charge time of capacitor with measured capacitance C_X to previously accepted threshold voltage value on its plates; t₂ - charge time of parallel circuit from capacitors C_X and C_O to previously accepted threshold voltage value on their plates.

EFFECT: technical result that can be achieved by proposed method for measuring electrical capacity, is aimed at eliminating effect of voltage E changing of DC source, resistance R of resistor in charge circuit of capacitor with measurable capacitance C_X, on measurement result, that is to increase accuracy of measuring electrical capacity.

1 cl, 1 tbl, 3 dwg