SU1659883A1 - Method of simultaneous and non-contact measuring direct current and voltage - Google Patents

Abstract

The invention relates to a radio metering technique and can be used to efficiently measure voltages and currents in high voltage circuits. The purpose of the invention is to improve the measurement accuracy by using the MIS-triode structure, as well as by achieving the maximum possible current value of its input circuit by choosing the exposure time of the measuring electrode equal to the constant induction time on the measuring electrode of the total charge and selecting the shielding time of the measuring electrode equal to the readout time of the signal corresponding to the drainage time of the total charge induced on the measuring electrode through the input resistance ix MIS triode structure -dostigaets in that the measurement of the electric field is carried out MIS triode structure formed straight and inverted signals which affect conditioners voltage and current, in synchronization with the commute to the ground. The shielding and measuring electrodes, the exposure time of which is maintained equal to the constant induction time on the measuring electrode of the full electric charge, and the shielding time maintained equal to the constant reading time of the signal from the measuring electrode. A device that implements the method contains a conductor 1, a reference resistor 2, a shielding electrode 3, a measuring electrode 4, contact groups 5, an electronic switch b, impedance 7, an input circuit of a MIS-triode structure 8, a non-inverting impedance 9, a voltage driver 10 that inverts impedance 11, current driver 12 and digital measuring unit 13. 1 Il. Ј cl. 00 co.

Description

The invention relates to a radio metering technique and can be used to efficiently measure voltages and currents in high voltage circuits.

The aim of the invention is to improve the measurement accuracy by using the MIS-triode structure, as well as by achieving the highest possible

the value of the current of its input circuit by selecting the exposure time of the measuring electrode equal to the constant induction time on the measuring electrode full charge and selecting the shielding time of the measuring electrode equal to the reading time of the signal corresponding to the drain time of the full induced charge on the measuring electrode through the MOS- triode structure.

Contactless and simultaneous measurement of direct voltage and direct current by the proposed method is carried out as follows. A measuring electrode made of an electrically conductive material, usually of a disk shape, is placed in the zone of action of an electric field of a source of direct voltage and current, and a second electrode, the area of which is not smaller than the area of the measuring electrode, also made of an electrically conductive material is placed in front of it. The measuring electrode is galvanically connected to the control electrode (gate) of the MIS triode structure, and also connected to ground via the contact group of the electronic switch. Also, through a different contact group of the same electronic switch, the shielding electrode is connected to ground. The non-inverting and inverting output circuits of the MIS-triode structure include loads, usually resistive, that are electrically connected to a voltage and current driver.

Periodic exposure and shielding of the measuring electrode is performed.

At the stage of exposure, when the contact groups of the electronic switch disconnect the shielding and measuring electrode from the ground, the shielding electrode is transparent to the external electric field E generated by a source of constant voltage and current, i.e. It does not affect the magnitude of the field E acting on the measuring electrode and an induced charge occurs on it Q ea ES (1), which creates the potential p - c e E S / C, where Ba is the absolute dielectric constant of the medium; E is the voltage of the electric field of the constant voltage source acting on the shielding electrode; C is the total capacitance of the measuring electrode and the MIS triode structure.

When a shielding electrode is connected using the contact group of the electronic switch to ground, i.e. at the screening stage, this electrode completely isolates the measuring electrode from the external field E and the charge accumulated on it flows through the input resistance of the MIS-triode structure, made with an insulated gate and having

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high input impedance. By periodically exhibiting — shielding the measuring electrode — an alternating electrical signal is generated on it, which represents a variable voltage from 1) when exposed to zero during shielding. The alternating voltage on the measuring electrode creates a current in the input circuit of the MIS triode structure dE / dt U / ZBX AO / At (3) and the voltage in the input circuit, where U is the instantaneous value of the voltage on the measuring electrode; zBx is the total input impedance of the MIS triode structure.

The change in charge A Q includes its increase on the measuring electrode at the stage of exposure — AQ (+} and the decline of charge induced at the measuring electrode — Л0 (-) - at the screening stage, i.e. AQ Q + + D Q- (4)

The current generated in the input circuit of the MOS-tri-structure as a result of periodic shielding and exposure of the measuring electrode is written by the expression including two components: i AQ4 / Ati, (5) where Ati tes is the exposure time of the measuring electrode;

 the shielding time of the measuring electrode.

To accomplish this goal - to improve the measurement accuracy, it is necessary to achieve the maximum possible current value in the input circuit of the MIS-triode structure, since the voltage at its gate is UsHZex. This is achieved in the proposed method by selecting the time of exposure of the measuring electrode equal to the constant time n of induction on the measuring electrode of the total (maximum possible) charge Q, i.e. tes TI and the selection of the screening time of the measuring electrode equal to the time of reading the signal G2, corresponding to the time of the total charge induced by the measuring electrode through the input resistance of the MIS-triode structure. This time is determined mainly by the magnitude of the impedance of the switching circuit of the measuring electrode to the ground (screening stage), and in accordance with the expression (opt AQ -t- / Ti + AQ- / Г2 should be the minimum possible for this type of electronic switch ( -). Since the potential (relative to earth) of a source of constant voltage,

representing a circuit containing a conductor with a reference resistor, is proportional to the intensity of the electric field E acting on the electrode, then the voltage across the gate of the MIS triode structure is also proportional to the potential of the DC source, i.e. applied to this circuit constant voltage (). When using the linear region of the drain - gate characteristics of the MDP-triode structure, a current flows in its output circuit, proportional to the source voltage, i.e.

lBb., (6)

where U is the measured DC voltage;

Ki, K2 - proportionality coefficients;

S is the slope of the drain-slide characteristic. The flowing current Output creates a direct U + signal in the source circuit, which is proportional to the potential of the wire behind the reference resistor, i.e. proportional to the controlled constant voltage, and in the drain circuit, the inverse signal U-, proportional to the voltage drop across the reference resistor, i.e. voltage U IR3 or U-K3I, where I is the measured direct current, Cs is the proportionality coefficient.

The direct signal U + generated on the output circuit of the MIS-triode structure is applied to the voltage driver and the U- signal to the current driver.

The signals from the outputs of the voltage and current drivers via the analog signal part of the electronic switch act on the digital measuring unit, where they are converted into binary digital codes, decrypted and recorded on a digital display, which reflects the values of DC and current controlled in a contactless manner.

The described method for the simultaneous and non-contact measurement of DC voltage and current is implemented by a device whose structural diagram is shown in the drawing.

The device contains a closed circuit of a source of direct voltage, including conductor 1 and the reference resistor 2. The shielding electrode 3 and the measuring electrode 4 are connected to the zero bus through the contact groups 5 of the electronic switch 6. In the switching circuit of the measuring electrode 4 in series with the contact group 5 included impedance

7, connected in parallel to the input circuit of the MDP-triode structure 8. Its non-inverting impedance 9 is connected to the first input of the electronic switch 6 via the voltage shaper 10. The inverting impedance 11 is connected to the second input of the electronic switch 6 through the current shaper 12, the output of which is connected

with the input of the digital measuring unit 13.

The method is implemented as follows. In a closed circuit of a constant voltage source, including a conductor

1 and a reference resistor 2, for example, an anode circuit of a kinescope, supplies a DC voltage. In a closed circuit on the reference resistor 2, the voltage drops, which is proportional to

this DC circuit. Next, the electrical field E of the conductor 1 is applied by the reference resistor 2 to the system of the shielding electrode 3 - measuring electrode A, which are switched by the contact groups 5 of the electronic switch 6 to the ground. The electronic switch 6 contains a control part including, for example, a reference pulse generator, a one-shot, two tristable

an element representing contact groups 5; and an analog signal part representing an analog switch.

Impedance 7 determines the screening time constant of the measuring

electrode G2. At the stage of exposure, when the contact groups 5 of the electronic switch 6 are open, charge Q is induced on the measuring electrode 4. The exposure time constant for

system measuring electrode 4 - MDP triode structure 8 with a total capacitance of C 10-100 pF is n -

The screening steps, when the contact groups 5 of the electronic switch 6 connect the shielding electrode 3 directly, and the measuring electrode 4 through the impedance 7 to the ground, the duration of this stage is chosen equal to the constant time of the charge-draining circuit

from the measuring electrode 4. ten - . As shown by the results of the experiment, the optimal value of the current in the input circuit of the MIS-triode structure 8

IT IS POSSIBLE TO RECEIVE IF tes teK, i.e. G1 G2

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The alternating voltage of the gate in the input circuit of the MDP-triode structure 8 generates a current in its output circuit, which at its non-inverting impedance 9 generates a voltage proportional to the measured voltage, and at its inverting impedance 10 forms a voltage U- proportional to the measured current, i.e. where U.I is the measured DC voltage and current; , Ks - coefficients of proportionality.

The U + signal acts on the voltage driver 10, and the U signal on the current driver 12, at the output of which information signals of the required amplitude and frequency are formed.

Via an electronic switch b, the information signals received in the voltage driver 10 and current driver 12 are sent to digital measurement unit 13.

Claims (1)

The invention of the method of simultaneous and non-contact measurement of constant voltage and current by periodic exposure to AA 0 five 0 protected by a fixed shielding electrode measuring electrode of the electric field of the voltage source, sequential exposure and shielding, reading the signal by the sensitive element from the measuring electrode, amplifying and registering it, which is characterized in that the MIS is measured by the electric field to improve the measurement accuracy -triod structure, form a direct and inverse signals, which affect the voltage and current drivers, and simultaneously synchronize to the ground raniruyuschy and the measuring electrodes, the exposure time which is maintained at a constant time at the measuring electrode inducing the total electric charge, and the shield is maintained at the time of the time constant of the read signal from the measuring electrode.