SU1449914A1 - Voltage calibrator - Google Patents

Abstract

The invention relates to the field of electrical measurements and m. used in transferring the size of RF and microwave voltage units in coaxial transmission paths from exemplary measuring instruments to working measuring instruments. The purpose of the invention is to improve the accuracy and expand the frequency range of comparable voltages. To achieve the goal, two additional conductors were introduced into the device, a dual on / off switch, a low-frequency generator, and a half-wave-matched measure of the wave resistance of the passage type, with each semiconductor thermistor made of heat-coupled with three pins. The invention allows for the stabilization of the conductors and resistances of each of the thermistors when the level of the compressed voltages varies and, moreover, the comparator reads independently of the impedance of the comparative measuring instruments. 2 Il. from the next

Description

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The invention relates to the field of electrical measurements and can be used in transferring the size of a unit of RF and microwave voltage in coaxial transmission paths from exemplary measuring instruments to working measuring instruments1.

The purpose of the invention is improving the accuracy and widening the frequency range of comparable voltages,

Figure 1 shows a structural voltage calibrator circuit; Fig. 2 shows a cross section of a voltage transducer of a calibrator of voltages in the switching plane of semiconductor thermistors "

The voltage calibrator contains a high-frequency generator 1j connected by an output to the input of the voltage measuring transducer 2.

The measuring transducer 2 contains a coaxial line through passage consisting of input external conductor 3, connecting nut of input connector 4 of converter 2, output external conductor 5, input internal conductor 6 fixed on supporting dielectric washer 7, output internal conductor 8 connected with the input internal conductor 6, a heat-coupled semiconductor thermistor 9, having three leads 10-12, and a heat-coupled semiconductor thermistor 13, also with three leads 14-1 6 The terminals 10 and 14 of thermistors 9 and 13 are connected to the input inner conductor 6 in the transverse plane of the measuring converter 2, which is perpendicular to the axis of the converter 2.

In this transverse plane, symmetrically with respect to the inner conductor 6, terminals 11 and 15 of thermistors are connected to the first plates of the main capacitors 17 and 18

9 and 13, respectively, and the first plates of the additional capacitors 19 and 20 are connected to terminals 12 and 16 of thermistors 9 and 13, respectively. The second capacitor plates 17-20 are connected to the input external conductor 3 of the converter 2.

The output outer conductor 5 and the outward inner conductor 8 form the output length of the coaxial line, terminated with a standardized socket-type connector,

connected to the switch-on plane of thermistors 9 and 13. Connect the socket of the measuring converter 2 is connected by an input connector such as a half-conductor plug 2 measure of wave resistance of the passage type, consisting of external conductor 22, connecting nut of input connector 23 and internal conductor 24. To output connector An outlet type of wave-resistance measure 21 connects a voltage to be compressed by means of the measurement.

A self-balancing DC thermistor bridge 25 is connected to the first plates of the capacitors 17 and 18, to which the transmitter / counting device 26. is connected. The first pair of output capacitors 17 and the first 19 capacitors connected to the thermistor resistor are connected to the first skins. contacts of the double on-off switch 27. To the first plates of the main 18 and additional 20 capacitors connected to the thermistor 13, a second pair of output contacts of the switch 27 is connected. To the input pair of contacts is a switch tel 27 through the capacitors 28 and 29 connected to the output of the generator 30 low frequency. The output voltage of the low-frequency generator 30 is continuously adjustable. Since the thermally coupled semiconductor thermistor with three pins is symmetrical about its average output, there are three options in the calibrator for connecting the pins of thermistors between the input inner conductor 6 of the converter 2 and the first capacitor plates

17-20.

In the first version, as the terminals 10 and 14 of thermistors 9 and 13, connected to the input inner conductor 6 of the converter 2, the first extreme leads of thermistors 9 and 13о are used. As outputs 11 and 15, connected to the first plates of the main capacitors 17 and 18, the average terminals of thermistors 9 and 13 are used. As the terminals 12 and 16 connected to the first plates of the additional capacitors 19 and 20, the second extreme terminals of thermistors 9 and 13 are used.

In the second variant, as outputs 0 and 14 thermistors 9 and 13,

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connected to the input internal conductor 6 of the converter 2, use the average terminals of thermistors 9 and 13. As the conclusions II and 15, connected to the first plates of the main capacitors 17 and 18, use the first extreme terminals of thermistors 9 and 13, and as conclusions 12 and 16 Connected to the first plates of additional capacitors 19 and 20, use the last terminals of thermistors 9 and 13.

In the third variant, as the terminals 10 and 14 of the thermistors 9 and 13 connected to the input inner conductor 6 of the converter 2, the first extreme terminals of the thermistors 9 and 13 are used. As the terminals 11 and 15 connected to the first plates of the main capacitors 17 and 18, the first extreme conclusions of thermistor 9 and 13. As conclusions 12 and 16, connected to the first plates of additional capacitors 19 and 20, use the average terminals of thermistors 9 and 1

The calibrator works as follows.

At the beginning of work at the outputs of the high-frequency generator 1 and the low-frequency generator 30, the output signal level is set to zero.

In the initial state of the calibrator, the working resistance of the thermistor bridge 25 is set equal to the value at which the maximum permissible power dissipation is dissipated by the thermistors. In this case, the maximum possible voltage values can be compiled.

The constant current of the self-balancing thermistor bridge 25 flows through the thermistor 9 from its terminal 11 to terminal 10 and through the thermistor 13 from its terminal 1 to terminal 15. Because thermistors 9 and 13 differ from each other in sensitivity, mass, heat capacity, you need The difference is in their resistance to direct current. To do this, before carrying out measurements, an auxiliary segment of a coaxial line is connected to the outlet connector of the socket type of the measure 21 of the impedance of the passage type, between which the external and internal conductors

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Kami included high frequency choke. The indicated line segment with a choke is necessary for direct current closure of the input and output, external conductors 3 and 22 of the converter 2 and measure 21 of the impedance with their input and output internal conductors 6 and 24.

From the ratio of the voltages between the outer conductor 3 of the converter 2 and, accordingly, the first plate of the capacitor 17 and the first plate of the capacitor 18, it is determined which of the thermistors has a greater resistance. Switch 27 is then set in a position in which generator 30 is connected to a high-resistance thermistor. The high-frequency generator 1 sets the maximum level of the high-frequency voltage at which the high-frequency power dissipated by the thermistors is 85-90% of the bias power of the thermistors. The high-frequency current of the generator 1 flows through the input inner conductor 6 of the measuring converter 2 and splits in four parallel circuits. In the first of these circuits, the high-frequency current flows from terminal 10 to output

11 thermistor 9 and through the capacitor 17 is closed on the input external conductor 3 of the Converter 2. In the second of these circuits high-frequency

current flows from output 10 to output

12 thermistor 9 and through the capacitor 19 is closed to the external input conductor 3 of the converter 2. B of the third of these circuits, high-frequency current flows from pin 14 to terminal 15 of the thermistor 13 and through the capacitor 18 closes to the input external conductor 3 of the converter 2. In the fourth of these circuits, high-frequency current flows from the output

14 to the output 16 of the thermistor 13 and through the capacitor 20 is closed on the input external conductor 3 of the converter 2.

Thus, through the input external conductor 3 to the high-frequency generator 1, a high-frequency current flows of the same magnitude as the current through the input internal conductor 6 of the converter 2. When high-frequency currents flow through the thermistors 9 and 13, the DC current of the bridge 25

51

automatically decreasing, thus ensuring the constancy of the sum of the resistances of the thermoreistor 9 between its terminals 10 and 11 and the thermistor 13 between its terminals 14 and 15. The thresholds of the resistances of the thermistors 9 and 13 change in relation to their values in the absence of high-frequency currents as thermistors have different sensitivities, resistances and conductivities.

Then set the zero output level of the high-frequency generator 1 and first a small initial level at the output of the generator 30.

The ratio of the resistances of thermistors 9 and 13 is measured. Then the maximum output level of the high-frequency generator 1 is applied to y and the resistance ratio of the thermistors is measured again at the zero output level of the generator 1, the output level of the generator 30 is also increased, and at the zero output level of the high-frequency generator 1, the resistance ratio of thermistors 9 and 13 is measured. As the output signal of the generator 30 increases, the resistance of the thermistor with a large initial resistance decreases, and the resistance ivlenie another thermistor increases

Thus, gradually increase the output level of low-frequency generator 30 until those nopj until they get the same ratio of resistances of thermistors 9 and 13 at zero output level of high-frequency generator I and at maximum output level of generator 30. In this case, the increment of DC power is on each of the thermistors is equal to the increment of the power of the high-frequency current, which provides a condition for the stabilization of the resistances of the conductivities of the thermistors 9 and 13, in which the ratio of their resistance This is the ratio of their conductivities.

By adjusting the desired output level of the low-frequency generator 30, this level is subsequently maintained constant throughout the entire measurement at a given frequency.

Then, the auxiliary segment of the coaxial line containing the high-frequency choke is disconnected from the output of the outlet of measure 21

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resistances and connect instead an exemplary voltage measurement instrument.

An exemplary voltage measurement instrument is calibrated against the voltage in its reference measurement plane. In the overwhelming number of cases, the input plane of the coaxial connector included at the input of an exemplary measuring instrument, i.e. the beginning of the regular part of the inner conductor of the coaxial connector. However, in some cases, the reference measurement plane can be selected at some distance from the input plane of the coaxial connector to improve measurement accuracy. In this case, between the input and reference measurement planes is included a segment coaxial with a characteristic impedance equal to the characteristic impedance of the coaxial line of a certain size.

The wave resistances of the coaxial line segment, consisting of the output outer conductor 5 and the output inner conductor 8 of the measuring transducer 2 and the measure 21 of the impedance consisting of the outer conductor 22 and the inner conductor 24, are equal to the characteristic impedance of the coaxial line, and the length of the measure 21 of the impedance in each case, is chosen such that between the switching-on plane of the thermistors 9 and 13 of the converter 2 and the reference measuring plane of the reference or calibrated means from voltage measurement turned on an air coaxial line with a characteristic impedance equal to the line impedance, whose length is a multiple of half the wavelength in the coaxial line, thus ensuring the independence of the RF and microwave voltage calibrators from the impedance of the reference or verifiable voltage measurement device.

The calibrator calibration coefficient is found, which is equal to the ratio of the measured voltage on an exemplary measuring instrument to the averaged reading of the UK calibrator reading device:

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where and ° -4-; zT- (and

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to K

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where about - the ratio of resistance

thermistors;

, - DC voltage at thermistors 9 and 13, equal to the output voltage of the thermistor bridge at the zero output level of the generator 1 and at the level that ensures the correctness of the calibrator readings, respectively. An exemplary measuring instrument is disconnected, and a testable 15 voltage measuring device is connected to the output of the measure 21 of impedance. In this case, the test instrument should have a reference measurement plane at the same distance from the connector reference plane as 20 for an exemplary measurement instrument. Otherwise, a wave impedance measure of a different length should be used, providing half-voltage to a coaxial voltage measuring transducer the cross section of which contains two semiconductor ball-type thermistors connected by the first leads to the inner conductor of the coaxial measuring transform bodies, and the second terminals to the first plates of two capacitors, the second plates of which are connected to the outer conductor of the coaxial measuring transducer, the output segment of the coaxial line connected to the turn-on plane of the thermistors of the coaxial measuring transducer, self-capacitor low-voltage thermo-resistor DC bridge connected to the ground capacitor plates and indicator, characterized in that, with the aim of increasing the accuracy and expanding the frequency range of comparable voltages, They are two additional convoy air coaxial line inter-25 densator, dual two-position

The switching plane of the thermistors 9 and 13 of the converter 2 and ogg. calculating measuring plane

The calibrator reading device measures the voltage on thermistors 9 and 13 when the zero output level of the high frequency generator 1 is set, and then the voltage on the thermistors when the output level of the generator 1 UK required for calibration is established.

The voltage value on the comparator uj) is calculated by the formula

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2GT +) At the same time, the voltage value is measured on a calibrated U voltage measuring instrument. The actual voltage value in the reference plane of the calibrated measuring instrument is calculated using the formula i.pdys.-Ki ;:.

Claims (1)

Invention Formula " five A voltage calibrator containing a high-frequency generator connected to a coaxial voltage measuring transducer, in cross section of which there are two semiconductor pinch thermistors connected to the inner conductor of the coaxial measuring transducer with the second terminals to the first plates of two capacitors, the second plates of which are connected with an external conductor coaxial measuring transducer, the output segment of the coaxial line connected to the plane bone incorporation thermistors coaxial transducer, samobapansir toschiys morezistorny thermal bridge dc connected to the first capacitor plate and the indicator, characterized in that, in order to increase the accuracy and the frequency band expansion kompariruemyh stress, two additional con administered so 40 45 50 switch, low-frequency generator, matched half-wave measure of the impedance of the passage type, in this case each semiconductor thermistor is heat-coupled with three terminals, the third output of which is connected to the first plate of the additional capacitor, the second plate of which is connected to the external conductor of the coaxial measuring converter, the first pair output contacts of a double two-position switch are connected to the first plates of the main and additional The switches connected to the first thermistor, and the second pair of output contacts are connected to the first plates of the main and additional capacitors connected to the second thermistor, the output of the low-frequency generator is connected to the input pair of contacts of the dual two-position switch, and the pass-through resistance measure is connected to output of the coaxial line cut. T 30 (riv. 1 . nineteen 12 20 Fie.2