Patent CZ-306726-B6 (CZ)
Title: A method of measuring rapid changes of low values of surface conductivity of dielectrics in the environment of electromagnetic interference of mains voltage and a device for performing this method of measuring
Inventor: FRYČÁK PETR
IPC: G01R27/04
Filed: 2016-06-30
Abstract: The method of measuring rapid changes of low values of surface conductivity of dielectrics in the environment of electromagnetic interference of mains voltage is based on comparative measurement on a voltage divider and synchronization of measuring pulses with a periodic sinusoidal course of interference, when the tested dielectric surface is supplied with voltage of determined parameters of the rectangular pulse, while on the voltage divider formed from the measured dielectric surface and a resistor of a selected resistance value, there is sampled the potential at certain time intervals, partly before inserting the measuring pulse and partly just before its end, when then, based on the difference of the measured values by the differential amplifier, the value corresponding to the value measured without the influence of electromagnetic interference of 50 Hz is obtained, where the result is enabling the measurement of rapid changes of low values of surface conductivity of dielectrics. The device for measuring rapid changes of low values of surface conductivity of dielectrics in the environment of electromagnetic interference of the mains voltage comprises the monitoring element (1) of electromagnetic interference which is connected to the block (2) for monitoring electromagnetic interference, whose first output is connected to the comparison block (3) for controlling the generation of time sequences and the block (4) of formation of pulses, whose output of the rectangular pulse of 1 ms/.+-. 5 V and the second output of 10 .mi.s/.+-.5 V are connected to the individual inputs of the block (6) of logic elements, while the other output of the block (2) for monitoring electromagnetic interference is connected to the comparison element (5), whose output is connected to the fourth input of the block (6) of logic elements, while the first output of the block (6) of logic elements is connected via the block (7) of pulse modulation with the pulse output ranging from 0 to 300 mV on the probed surface of the block (8) of the voltage divider of the surface/resistor of the divider, where the output of this block (8) of the voltage divider of the surface/resistor of the divider is connected, via the block (11) of voltage tracker on the divider with a very high input impedance, to the signal inputs of the first sample-and-hold amplifier (9) and the second sample-and-hold amplifier (10), while the second input for controlling the sampling of the first sample-and-hold amplifier (9) and the second input for controlling the sampling of the second sample-and-hold amplifier (10) are connected to the corresponding outputs for controlling the sampling of the block (6) of logic elements, while the output of the first sample-and-hold amplifier (9) is connected, via the block (12) of two series-connected inverting amplifiers, to the inverting input of the differential amplifier (13), whose non-inverting input is connected to the output of the second sample-and-hold amplifier (10), while the differential amplifier (13) is connected to the output from the device via the block (14) of elimination of the random signal fluctuation and the output block (15) with a low impedance.