RU2245557C1 - Method and device for resistance measurements - Google Patents

Abstract

FIELD: measurement of low resistances.

SUBSTANCE: prior to starting measurements temperature control unit transfers signal indicating that working temperature is attained in central processor unit. Then current generator unit produces first desired current in measuring circuit. Central processor unit selects gain of reference and measuring channels at steady state current in compliance with measurement range and sends instruction to measuring channel amplifier unit to measure amplifier zero offset. After that digital-to-analog converter reduces reference voltage, and amplifier gain is adjusted. Then amplifier zero offset is measured in reference channel whereupon instruction is conveyed to measuring unit amplifier unit for measuring voltage at known resistance.

EFFECT: enhanced reliability, measurement accuracy, and speed, extended measurement range.

23 cl, 4 dwg

Description

The invention relates to the field of electrical measurements and can be used to measure small active resistances.

A known method of measuring the magnitude of the resistance (EP No. 0483494), based on measuring the voltage drop across the measured resistance, which maintains a constant measuring current through the measured resistance using an operational amplifier, and changing the measurement limits is made by connecting one reference resistance from the group. Such an approach is not possible when measuring the resistance of an inductive object, because in this case, the time interval from the moment the measuring circuit is turned on until stable readings are established will be very long, the voltage generated at the reference resistance is not measured, and generation of an always known current value is required to ensure the measurement accuracy.

A device for measuring the magnitude of the resistance (patent EP No. 0483494), containing a reference voltage source connected to an operational amplifier, which is connected with a non-inverting input to one of the poles of the reference voltage source, and the inverting input of the reference amplifier is connected to a supply cable that is connected to the first input reference resistance, the second input of which is connected to the ground. The output of the first operational amplifier is connected through the measured resistance to the first nodal point, which is connected to the second supply cable, shown in the diagram as active resistance and connected to the first input of the reference resistance. The output of the first operational amplifier is connected to the input of the voltage subtraction circuit, the second input of which is connected to the first nodal point. The voltage subtraction circuit comprises second and third operational amplifiers and auxiliary resistance measurement circuits. The non-inverting input of the second operational amplifier, operating according to the impedance conversion circuit, is connected to the second input of the voltage subtraction circuit, and its inverting input is connected to its own output. The inverting input of the third operational amplifier is connected to the first connecting input of the voltage subtraction circuit through the first resistor and to its output through the second resistor, while the resistance values of the first, second, third, and fourth resistors are equal to each other.

The disadvantage of this device is that current can flow through resistors R1 and R2 if the potentials of point A1 and point E1 are not exactly equal to each other, and, as a result, the current flowing through the measured resistance is not known exactly, which affects accuracy of measurements. In addition, the measurement limits are switched using a set of reference resistors through controlled switches in the circuit of the measuring current flow, which may be unacceptable when working with inductive objects.

A known method of measuring electrical resistance (US patent No. 4698584), based on the use of capacitive discharge to create high current through the measurement object for a short time. With this method, the voltage drop across the reference resistance and at an unknown resistance is integrated in an analogue manner, followed by the calculation of the measured resistance.

This method is applicable for measuring ultra-low resistances of objects that have practically no inductive component. A measuring current is generated, a first signal corresponding to the magnitude of the measuring current is created, a second signal is created proportional to the magnitude of the measuring current and ultra-low electrical resistance, these signals are integrated with respect to time, starting from the same moment. The first integrated signal is compared with a reference signal having a predetermined amplitude, integration is stopped when a comparison of the first integrated signal with a reference voltage indicates that the integrated signal has reached a predetermined amplitude, and the second integrated signal has an amplitude that is a measure of ultra-low electrical resistance.

The disadvantage of this method is that this method is not applicable for inductive objects, such as transformers, where during the formation of a short-term current using a capacitive discharge, a stable voltage drop across the measured winding characteristic of this current is not established, in addition, a sharp change in current from the values about 30-20A to 0A in a short time causes the appearance of a large emf of self-induction, which can lead to equipment damage and risk to maintenance personnel.

A device for measuring resistance (US patent No. 4698584) is known, comprising a current source including a group of batteries for converting a constant voltage to a constant voltage, to increase the voltage amplitude to a desired level, while the current source charges a capacitor, which is actually an electric energy storage battery, and a resistor having a resistance selected to limit to a certain limit of the measuring current, the output of the current source is connected to a shunt resistor connected through a conducting th object having ultrasmall resistance, which should be measured with an electronic key, and a button type switch coupled at one input to ground and the second input - to the input of the pulse generator, which produces at its output pulses in response to the closure of a key. The pulse sequence is transmitted to the control circuit of each measuring cycle, the output of which is connected to an isolating and phase-shifting circuit connected by its output to an electronic key, as well as to a phase-shifting circuit having an output to a reset circuit connected to an integrator whose inputs are connected to the inputs of the resistor, and the output of the integrator is connected to one of the inputs of the comparator, the second input of which is connected through a voltage source to ground, the output of the comparator is also connected via a monostable reset circuit to the control circuit and through the second monostable circuit - with an indicator, and the amplifier includes two inputs connected to the object with measured resistance, and the output of the small signal amplifier is connected to the first input of the integrator, the second input of which is connected to the compensation capacitor, the integrator output is connected to the phase-shifting circuit through the reset circuit the circuit and through the switch - with the sampling circuit, while the output of the phase-shifting circuit is connected via an inverting circuit to the switch, and the sampling circuit is connected to the indicator device nation.

This device does not allow to take into account the requirements of the measurement object in terms of current and voltage, which can lead to equipment damage when working with inductive objects and damage to “pn” junctions when working with semiconductor elements.

A known method of measuring the value of impedance (GB patent No. 2166555), closest to the proposed, in accordance with which the first voltage is formed, apply the first voltage to a circuit containing an unknown impedance connected in series with a reference resistor, for the total current to flow through them, scale the first voltage in accordance with the selected number and get a second voltage, compare the second voltage with the voltage drop at an unknown impedance, change the value of the selected number so that lead weakened first voltage according to the voltage drop across unknown impedance as long as the second voltage is equal to a predetermined accuracy measured and used to indicate the number of the selected value of the unknown impedance.

The disadvantage of this method is that this attenuation undergoes voltage in the circuit section containing the reference impedance, unknown impedance and impedance of the lead wires, which leads to insufficient reliability and accuracy of the method. Using this method provides an accuracy of 1%, which is not acceptable for metrological measurements. In addition, this method eliminates the switching of measurement limits and provides a measurement range from 0.01 of the value of the reference impedance to 100 values of the reference impedance, which is far from enough for use in industrial facilities, in particular when testing transformers. In addition, the magnitude of the current flowing through the measurement object, the current rise rate when the voltage source is turned on, are not controlled, which does not allow using this method to measure the impedance of highly inductive objects. Also, the magnitude of the current flowing through the supply wires is not controlled, because of this it is impossible to provide a test of operability and verification of the reliability of connection to the object without auxiliary means. The lack of temperature control of the measuring circuit leads to insufficient accuracy and reliability of the method. This method also has insufficient speed when measuring the resistance of transformer windings due to lengthy transients associated with the establishment of a constant voltage on the winding of the measurement object with a current flowing through it.

A device for measuring impedance is known (GB patent No. 2166555), comprising a voltage source, an amplifier connected to a serial circuit containing unknown and reference impedances located between the output of the amplifier and ground, while the output of the amplifier is connected to the input of a digital-to-analog converter or programmable attenuator, output which is connected to the positive input of the comparator, the second input of which is connected through the register of successive approximations with a tap between the reference and measured resistances , the output of the comparator is connected to the digital inputs of the digital-to-analog converter.

The disadvantages of this method and device are as follows:

- insufficient measurement accuracy, since the temperature of the measuring circuit is not controlled and the accuracy of not more than 1% of the measured value is ensured, which is not acceptable for metrological measurements;

- insufficient performance when measuring transformer windings due to the long transient processes associated with the establishment of a constant voltage on the winding of the measurement object with a current flowing through it;

- insufficient measurement range due to the exclusion of switching of measurement limits;

- insufficient reliability due to the fact that the voltage used in the circuit section containing the reference impedance, unknown impedance and impedance of the supply wires is used as the reference voltage, and the magnitude of the current flowing through the measurement object is not controlled;

- the inability to verify the operability and reliability of the connection to the object without auxiliary means, since the magnitude of the current flowing through the supply wires is not controlled.

The technical result is expressed in the improvement of the method and device for measuring active resistance.

The technical problem solved by the proposed methods and devices is aimed at improving the accuracy of measurement, increasing speed, expanding the measurement range, increasing reliability, checking the reliability of the connection of the object.

To solve the problem by the known method of measuring the active resistance, which consists in applying a first voltage to a circuit containing an unknown resistance connected in series with a reference resistor, for the total current to flow through them, form a reference voltage, form the product of the reference voltage and the selected number , change the value of the selected number so as to bring the weakened reference voltage in accordance with the voltage drop at an unknown resistance and, and use the selected number to indicate the value of the unknown resistance, according to the invention create and maintain the temperature inside the measuring device in predetermined limits, form the specified measuring current in the measuring circuit by gradually increasing it from zero to a given fixed value and then maintaining this value, choose gain factors for amplifiers of the reference and measuring paths; they measure the zero bias of the amplifiers and measure the voltage drop across the reference resistor and the unknown resistance relative to the generated reference voltage, the value of the unknown active resistance is determined based on the obtained value of the voltage drop across the reference resistor and the unknown resistance, the zero bias of the amplifiers and the exact value of the resistance of the reference resistor, while the value of the unknown resistance is determined by the formula:

Rх = (Uin2-Unl2) * K1 * Ret / ((Uin1-Unl1) * K2), where:

Rx is the value of the unknown resistance;

Uin2 - voltage measured by an analog-to-digital converter unit at an unknown resistance;

Un2 - zero offset voltage of the amplifier of the measuring path at the selected gain K2;

K1 is the gain of the amplifier block of the reference path;

Ret is the resistance value of the reference resistor at a given operating temperature;

Uin1 is the voltage measured by an analog-to-digital converter unit on a reference resistor when a measuring current flows through it;

Unl1 - zero bias voltage of the amplifier of the reference path at the selected gain K1;

K2 is the gain of the amplifier unit of the measuring path.

According to the invention:

- pre-measure the value of the voltage drop across the reference resistor and the unknown resistance, the zero offset of the amplifiers of the reference and measuring paths with a gain equal to unity, to determine the limit of measurement;

- all measurements are carried out with a frequency of at least 1 kHz.

2. To solve the problem by a known method for measuring the active resistance of a transformer winding, which consists in applying a first voltage to a circuit containing an unknown resistance connected in series with a reference resistor, for the total current to flow through them, form a reference voltage, form the product of the reference voltage and the selected number, change the value of the selected number so as to bring the weakened reference voltage in accordance with the voltage drop n unknown resistance, and the selected number is used to indicate the value of the unknown resistance, according to the invention, the temperature inside the measuring device is created and maintained within predetermined limits, a predetermined measuring current is generated in the measuring circuit by gradually rising from zero to a given fixed value, and then maintaining this value, on the free winding of the transformer form a train of pulses of preparation of the measured winding of the transformer until If a constant voltage drop is not established on the latter, gain factors for the amplifiers of the reference and measuring paths are selected, a zero bias is measured for the amplifiers and a voltage drop is measured at the reference resistor and an unknown resistance with respect to the generated reference voltage, a zero measuring current is generated in the measuring circuit by smooth decrease from the set value to zero, on the free winding of the transformer form a pulse train and the measured transformer winding until a negligible voltage drop is established on the latter, while the value of the unknown active resistance of the measured transformer winding is determined based on the obtained value of the voltage drop across the reference resistor and the unknown resistance, zero bias of the amplifiers and the exact value of the resistance of the reference resistor , while the value of the unknown resistance is determined by the formula:

Rх = (Uin2-Unl2) * K1 * Ret / ((Uin1-Unl1) * K2), where:

Rx is the value of the unknown resistance;

Uin2 - voltage measured by an analog-to-digital converter unit at an unknown resistance;

Un2 - zero offset voltage of the amplifier of the measuring path at the selected gain K2;

K1 is the gain of the amplifier block of the reference path;

Ret is the resistance value of the reference resistor at a given operating temperature;

Uin1 is the voltage measured by an analog-to-digital converter unit on a reference resistor when a measuring current flows through it;

Unl1 - zero bias voltage of the amplifier of the reference path at the selected gain K1;

K2 is the gain of the amplifier unit of the measuring path.

Moreover:

- a sequence of pulses of preparation of the measurement object is formed in such a way that the products of the amplitude and duration of the pulses make up an alternating series whose members decrease with increasing their serial number, and the pauses between pulses do not exceed the pulse duration;

- the shape of the pulse train of the preparation of the measurement object is changed until a time-stable voltage drop across the unknown resistance is achieved;

- a sequence of pulses of preparation of the measurement object is formed on several free transformer windings simultaneously.

3. To solve the problem, a known device for determining the active resistance, containing an unknown resistance in series and a reference resistor, a unit for generating a predetermined voltage in the measuring circuit, a programmable means for scaling the reference voltage, a comparator, an indication means, according to the invention is additionally equipped with a differential amplifier, amplifier units reference and measuring paths, the unit of preparation of the measurement object, the temperature control unit, In this case, the input-output of the central processing unit is connected to the input-output of the keyboard and display control unit, temperature control unit, object preparation unit, reference amplifier and measurement path amplifier blocks, analog-to-digital converter unit containing two identical circuits, each of which consists of serially connected adder, error amplifier and comparator, while the input-output of each comparator is connected to the input-output of the processor device, the digital outputs of which are connected to the current inputs of the digital-to-analog converter, the output of which is connected through the current / voltage converter to the inputs of the adders of both circuits, and the second input of the digital-to-analog converter is connected to the output of the reference voltage source, which is also connected to the inputs of the adders of both circuits, and the current generator block contains two generators, the output of the first the current generator is connected to the current input of the first reference resistor, the potential terminals of which are connected to the control inputs of the first generator, one of the output The second generator is connected to the current input of the second reference resistor through an unknown resistance, the potential terminals of the second reference resistor are connected to the inputs of the second generator and to the inputs of the differential amplifier connected to the amplifier of the reference path, the output of which is connected to the input of the adder of the first circuit of the analog-to-digital converter unit, and one of the conclusions of the unknown resistance is connected to the input of the amplifier unit of the measuring path, while the second output of the unknown resistance is connected nen common bus;

- the current generator is configured to control the magnitude of the current flowing through an unknown resistance, with the requirements of the current parameters;

- the current generator is made with the possibility of smooth adjustment of the measuring current in accordance with the voltage measured at an unknown resistance;

- the current generator is configured to generate at least four measuring constant currents, and the ability to smoothly increase the current from zero to the desired value and decrease from a fixed value to zero;

- the current generator is configured to use at least two current generators using, respectively, two reference resistors, with the ability to control the voltage across the reference resistors;

- the current generator is configured to generate zero current through one of the current generators and generate current from zero to a predetermined value through the second generator;

- the current generator is configured to use a capacitive discharge to create a short-term current of large magnitude, the magnitude of which can be maintained constant during the period of time required for measurement;

- the current generator is configured to generate current in the forward and reverse directions to take into account thermopower;

- the current generator is configured to connect to the current and potential terminals of the device and to issue an adjustable current through any pair of lead wires to ensure reliable connection;

- the unit for preparing the measurement object is configured to form an alternating sequence of pulses of a given shape, and the pauses between pulses do not exceed the pulse duration;

- the unit for preparing the measurement object is configured to generate a sequence of pulses during the formation of the current generator smoothly increasing or decreasing current, and the ability to adjust and change the mode depending on the magnitude of the current and the mode of operation of the current generator;

- the unit for preparing the measurement object is configured to adjust and change the shape of the sequence of issued pulses depending on the measurement result;

- the unit for preparing the measurement object is configured to control the current flowing through the free winding of the measurement object (transformer);

- the unit for preparing the measurement object is made with the possibility of connecting to several free transformer windings simultaneously with the formation for each of them of a given sequence of voltage pulses of alternating polarity.

Creating and maintaining the temperature inside the measuring device within the specified limits using the temperature control unit allows you to set the operating temperature of the circuit within the specified limits, which ensures the invariability of the electrical characteristics of the circuit elements, including the reference resistor, which ultimately improves the accuracy of measurements.

The formation of the measuring current in the measuring circuit by gradually increasing it from zero to a predetermined fixed value and then maintaining this value with the help of a current generator makes it possible to exclude the influence of transients on the measurement result, which increases the measurement accuracy. In addition, the requirements for current flowing through an unknown resistance are provided, which increases the reliability of the method.

The choice of amplification factors for amplifiers of the reference and measuring paths using the unit of the central processing unit allows you to more accurately adjust the measurement process and use the analog-to-digital conversion unit with maximum efficiency, which allows you to expand the measurement range and improve the measurement accuracy.

The measurement of the zero offset of the amplifiers using the analog-to-digital converter unit allows you to take into account the error introduced by the amplifiers, which increases the accuracy of the measurement, especially when measuring ultra low resistances.

The formation of the reference voltage using the reference voltage source increases the reliability of the method, since it becomes possible to measure the voltage drop on the reference resistor and the unknown resistance and zero bias of the amplifiers relative to the same time-constant reference voltage generated inside the measuring circuit. It also eliminates the uncertainty of the measurement result when a break in the measuring circuit due to the lack of a reference voltage taken from the measuring circuit, which increases the reliability of the method. In addition, the use of an independent stabilized reference voltage generated inside the measuring circuit allows to increase the accuracy of the measurement in contrast to the use for this purpose of a voltage drop in the measuring circuit, which may be unstable due to internal processes in the measurement object and interference to the lead wires.

Determining the value of the unknown active resistance on the basis of the obtained value of the voltage drop across the reference resistor and the unknown resistance, the zero bias of the amplifiers and the exact value of the reference resistor at a given operating temperature allows us to take into account the main factors affecting the measurement error and to eliminate their influence, which will significantly increase the accuracy measurements.

Preliminary measurement of the voltage drop across the reference resistor and unknown resistance, as well as measuring the zero offset of the amplifiers of the reference and measuring paths with a gain equal to unity, allows you to quickly evaluate the value of the unknown resistance and determine the measurement limit at which to accurately measure the unknown resistance, which improves the speed of the method.

The measurement of the voltage drop across the reference resistor and the unknown resistance, the zero offset of the amplifiers with a frequency of at least 1 kHz eliminates the influence of low-frequency fluctuations of the measuring current, and, thus, increase the reliability of the proposed method. In addition, this allows the averaging of the measured values over time or their integration over time, which increases the accuracy of the measurement.

Checking the connection to the object using the current generator allows you to verify the reliability of the electrical contact between the connecting terminals of the object and the connecting wires.

According to the 2nd variant of the method:

Creating and maintaining the temperature inside the measuring device within the specified limits using the temperature control unit allows you to set the operating temperature of the circuit within the specified limits, which ensures the invariability of the electrical characteristics of the circuit elements, including the reference resistor, which ultimately improves the accuracy of measurements.

The formation of the measuring current in the measuring circuit by gradually increasing it from zero to a predetermined fixed value and then maintaining this value with the help of a current generator makes it possible to exclude the influence of transients on the measurement result, which increases the measurement accuracy. In addition, the requirements are provided for the current flowing through an unknown resistance (for example, the limit value of the operating current flowing through the transformer winding), which increases the reliability of the method and the safety of operation.

The formation on the free winding of the transformer of the sequence of pulses of the preparation of the measurement object using the preparation unit of the object allows to achieve a more rapid establishment of a constant voltage drop at an unknown resistance (winding), which increases the speed of the method.

The choice of amplification factors for amplifiers of the reference and measuring paths using the unit of the central processing unit allows you to more accurately adjust the measurement process and use the unit of the analog-to-digital converter with maximum efficiency, which allows you to expand the measurement range and improve the measurement accuracy.

The measurement of the zero offset of the amplifiers using the analog-to-digital converter unit allows you to take into account the error introduced by the amplifiers, which increases the accuracy of the measurement, especially when measuring ultra low resistances.

The formation of the reference voltage using the reference voltage source increases the reliability of the method, since it becomes possible to measure the voltage drop on the reference resistor and the unknown resistance and the zero bias of the amplifiers relative to the same time-constant reference voltage generated inside the measuring circuit. It also eliminates the uncertainty of the measurement result when a break in the measuring circuit due to the lack of a reference voltage taken from the measuring circuit, which increases the reliability of the method. In addition, the use of an independent stabilized reference voltage generated inside the measuring circuit allows to increase the accuracy of the measurement in contrast to the use for this purpose of a voltage drop in the measuring circuit, which may be unstable due to internal processes in the measurement object and interference to the lead wires.

The formation of a zero measuring current in the measuring circuit by gradually decreasing from a predetermined value to zero using a current generator allows you to leave the object (transformer) in the state most suitable for subsequent measurements, which increases the reliability of the method. At the same time, operational safety is ensured when switching the measurement limits and when disconnecting the device from a highly inductive object (transformer).

The formation on the free winding of the transformer of a sequence of pulses of preparation of the measurement object until a negligible voltage drop with the help of the preparation unit of the object is established on an unknown resistance (winding), allows you to accelerate transients, which increases the speed of the method.

Determining the value of the unknown active resistance on the basis of the obtained value of the voltage drop across the reference resistor and the unknown resistance, the zero bias of the amplifiers and the exact value of the reference resistor at a given operating temperature allows us to take into account the main factors affecting the measurement error and to eliminate their influence, which will significantly increase the accuracy measurements.

The formation of a sequence of pulses of preparation of the measurement object using the preparation unit in such a way that the products of the amplitude and duration of the pulses make up an alternating series whose members decrease with increasing their serial number, the pauses between pulses do not exceed the pulse duration allows solving the technical problem - acceleration of transients.

Changing the shape of the pulse sequence by the preparation unit of the measurement object until a time-stable voltage drop at an unknown resistance is achieved, allows you to select the optimal transient acceleration mode, which further increases the speed of the method.

The formation of a sequence of pulses of preparation of the measurement object on several free transformer windings simultaneously using the preparation unit of the object allows creating conditions for a uniform transient flow inside the measurement object (transformer), which ensures high reliability of the method and operational safety.

According to claim 10 of the formula.

The supply of the device with a differential amplifier allows you to measure the voltage drop across the reference resistor relative to the common bus connected to one of the terminals of the unknown resistance, eliminates the influence of the supply wires on the measurement result, which allows to increase the measurement accuracy. In addition, it becomes possible to measure the voltage drop across the reference resistor and the unknown resistance using the same block of the analog-to-digital converter, which also increases the reliability of the device and the accuracy of the measurements.

The supply of the device with blocks of the reference and measuring paths allows you to accurately measure the voltage at an unknown resistance and the magnitude of the measuring current, which significantly increases the accuracy of the measurements. In addition, since the magnitude of the measuring current is accurately measured through the voltage drop across the reference resistor, there is no need for an ultra-stable DC source, which increases the reliability of the device. The separation of the voltage drop measurements on the reference resistor using the reference path block and the voltage drop on the unknown resistance using the measuring path block allows to increase the measurement accuracy, since excludes the influence of the resistances of the lead wires.

The introduction of an independent reference voltage source for measuring relative to the voltage generated by it at an unknown resistance and a reference resistor increases the reliability and accuracy of measurements, since the voltage is internal and stabilized, not connected to the measuring circuits, and is not subject to the influence of pickups on the wires or to the influence of internal processes in the measurement object, and does not depend on the integrity / interruption of the measuring circuit. The supply of the device with the unit for preparing the measurement object provides an increase in speed, reduction of the transient time when measuring the impedance of inductive objects, for example, the resistance of transformer windings.

The supply of the device with a temperature control unit improves the accuracy of the measurement by ensuring the invariance of the electrical characteristics of the measuring circuit, in particular the reference resistor, by maintaining a constant temperature inside the measuring device. This ensures high reliability of the device during long-term operation and in conditions of temperature changes.

Providing the device with a control unit for the keyboard and display provides the convenience of taking readings of the device, the ability to check the operability of the device and the reliability of connection to the object.

The implementation of the generator with the ability to control the magnitude of the current generated through an unknown resistance, with the provision of requirements for current and voltage increases the reliability of the device, because the generator generates a current that does not exceed the values allowed by the object. In addition, it provides improved measurement accuracy, because the current value is maintained constant during the measurement, which eliminates the influence of stray capacitances and inductances of the object and supply wires.

The implementation of the generator with the possibility of forming at least four measuring currents provides an extension of the measurement range in the absence of switching in the current circuit when switching the measurement limits.

The formation of a smoothly rising measuring current by the generator ensures operational safety when measuring the active resistance of inductive objects, because at highly inductive objects, an abrupt or abrupt change in the measuring current is unacceptable. At the same time, performance also increases, as with a smooth change in current, the time of transients decreases at inductive objects in comparison with a sharp change in current.

The execution of the block of the current generator of at least two generators using two reference resistors with the ability to control the voltage on the reference resistors provides improved measurement accuracy, because the necessary current stability is maintained both at small and at high current values.

The execution of the current generator block with the possibility of generating zero current through one generator and generating current from zero to a predetermined value through the second generator provides increased reliability, since it allows you to choose the value of the measuring current to meet the requirements of the measurement object to the current flowing through it and the applied voltage.

The implementation of the generator with the possibility of using capacitive discharge to create short-term current of large magnitude provides an extension of the measurement range, because with ultra-low active resistances on non-inductive objects, it is necessary to create a current of large magnitude.

The implementation of the current generator with the ability to generate current in the forward and reverse directions to take into account the influence of thermopower allows you to increase the accuracy of the measurement by eliminating the error introduced by thermopower.

The implementation of the current generator with the ability to connect to current and potential terminals and the issuance of an adjustable current through any pair of lead wires provides the ability to test the health and reliability of the connection to the object.

The execution of the unit for preparing the measurement with the possibility of forming an alternating sequence of pulses of a given shape, where the pauses between pulses do not exceed the pulse duration, provides improved performance, because transient time is reduced due to the oscillatory change in the magnetization of the transformer core.

The implementation of the unit for preparing the measurement object with the possibility of forming a sequence of pulses during the formation of the current generator smoothly increasing or decreasing current and the ability to adjust and change the operating mode of the current generator provides improved performance, because when approaching the magnitude of the current generated by the generator to a predetermined value of the measuring current, the magnetization of the transformer core asymptotically approaches the steady-state value.

The implementation of the unit for preparing the measurement with the ability to adjust and change the shape of the sequence of emitted pulses until a time-stable voltage drop across the unknown resistance is achieved, improves performance due to the fact that it is possible to choose the optimal mode of preparation of the measurement object, taking into account its response to impact formed. In addition, the reliability of the device and the accuracy of measurements are increased, because Measurements are correctly carried out only when the voltage drop at an unknown resistance is stable in time.

The implementation of the unit for preparing measurements with the ability to control the current flowing through the free winding of the transformer, improves the reliability of the device, because the current flowing through the free winding during the formation of the sequence of pulses of the preparation of the object does not exceed the permissible values.

The implementation of the unit for preparing measurements with the ability to connect to several free windings of the transformer simultaneously with the formation of a sequence of voltage pulses of alternating polarity for each of them provides an increase in the reliability of the method and operational safety, since conditions are created for a uniform course of transient processes inside the measurement object (transformer).

The proposed method for measuring active resistances (1st option) is implemented using a device presented in the form of a functional diagram.

Figure 1 shows a diagram of the device as a whole; figure 2. - a diagram of one embodiment of a current generator block; figure 3 - block diagram of the amplifier reference and measuring paths; figure 4 presents plots of the sequence of pulses of the preparation of the measured winding and the corresponding change in magnetic flux.

A device for measuring active resistance contains a central processing unit (CPU) 1, one of the inputs and outputs of which is connected to the input-output by the temperature control unit 2, the input-output of the preparation unit 3, the input-output of the amplifier unit 4 of the measuring path, its other input - the output is connected to the keyboard and display control unit 5, the third input-output of the central processing unit 1 is connected to the input-output of the current generator unit 6, the amplifier block of the reference path 7, the input-output of the processor device a block of an analog-to-digital converter 8, containing two identical circuits, each of which consists of a series-connected adder 9, an error amplifier 10 and a comparator 11, while the input-output of each comparator 11 is connected to the input-output of the processor device 12, one of the outputs the latter is connected to the input of the digital-to-analog converter 13, the output of which through the current / voltage converter 14 is connected to the inputs of the adders 9 of the block of the analog-to-digital converter 8, and the reference input of the digital-to-analog converter 13 connected to the output of the reference voltage source 15 connected to the inputs of the adders 9, the input of one of the adders 9 is also connected to the output of the amplifier unit 7 of the reference path, and the other to the output of the amplifier unit 4 of the measuring path.

The current generator unit 6 includes: a processor device 16, the digital outputs of which are connected to the corresponding digital inputs of the digital-to-analog converter 17, the reference input of which is connected to the reference voltage source 18, and the current output is connected to the input of the current / voltage converter 19, the output of which is connected to the main input the bias driver 20. The control input of the bias driver 20 is connected to the potential terminal 21 of the reference resistor 22, the first output of the bias driver 20 is connected to the first input m of the first generator 23, the second input of which is connected to the potential terminal 21 of the reference resistor 22. The output of the first generator 23 is connected to the current input of the reference resistor 24, the potential terminals of which are connected to the control inputs of the first current generator 23. The second output of the displacement driver 20 is connected to the managed switch 25, the permitting input of which is connected to the control output of the processor device 16, and the output of the control switch 25 is connected to the first input of the second current generator 26, the second input is It is connected to the potential terminal 21 of the reference resistor 22, and the control inputs of the second generator 26 are connected to the potential terminals of the reference resistor 22. The output of the second generator 26 is connected to the current input of the reference resistor 22 through a managed switch 27 having three outputs — A1, A2, A3, through a chain of resistances 28, 29 and an unknown resistance 30. Output A1 is connected to the current input of a reference resistor 22 through a chain of resistances 28, 29 and an unknown resistance 30; output A2 is connected to the current input of the reference resistor 22 through a chain of resistances 31, 30, 29; the output A3 is connected to the current input of the reference resistor 22 through a chain of resistances 32, 29. The second input of the switch 27 is connected to the output of the processor device 16. The outputs of the reference resistor 22 are connected to the inputs of the differential amplifier 33 through the control switch 34, the output of which is connected to the amplifier block of the reference path 7, the output of the latter is connected to the first input of the adder 9 (first chain) of the analog-to-digital converter unit 8.

The amplifiers blocks of the supporting path 7 and the measuring path 4 are made in two stages and have the same circuit.

The amplifier unit of the measuring path 4 contains two identical amplification stages, (Fig. 3 shows one amplification stage).

The cascade of the amplifier unit 4 contains a processor device 35, the digital output of which is connected to the digital inputs of the digital-to-analog converter 36, the reference input of which is connected to the output of the integrator 37, and the current output of the digital-to-analog converter 36 is connected to the input of the current / voltage converter 38, the output of which is connected to the compensation input the adder 39, the main input of which is connected to a managed switch 40, the enabling input of which is connected to the control output D5 of the processor device 35. The first contact The inventive switch 40 is connected to a potential terminal 41, and its second contact is connected to a common bus 42. 43 is a second potential terminal. The output of the adder 39 is connected to the input of the operational amplifier 44, the output of which is connected to the managed switch 45, and the output of the latter is connected to the input of the integrator 37, while their enable inputs are connected to the corresponding outputs of the processor device 35. The output of the integrator 37 is the output of the first amplification stage. The input / output of the processor device 35 is connected to the input / output of the CPU 1. The second amplification stage has an analogous circuit, the output of which is connected to the main input of the adder 9 of the analog-to-digital converter unit 8. The output of the preparation unit for the measurement object 3 is connected to the free winding of the measurement object 46 ( in the case of measuring the active resistance of the transformer windings).

Implemented the proposed method (1 variant of the method) measuring the active resistance using the proposed device as follows. The central processing unit 1, using the temperature control unit 2, provides the necessary temperature inside the device, constantly monitoring it and maintaining it in predetermined limits. The signal about the achievement of the operating temperature of the measuring circuit is transmitted to the CPU 1, which issues a command to the keyboard and display controller 5 and the latter displays the readiness of the device for measurements. The operator selects the mode (automatic or manual) and, if the manual mode is selected, selects the limit of measurement of the unknown resistance 30, controller 5 transfers this data to the CPU 1, which saves them and sends a command to the current generator unit 6 to form the first specified measuring current in the measuring circuit . At the same time, the current generator unit 6 generates a given measuring current in a circuit containing a reference resistor 22 and an unknown resistance 30 connected in series with it, by gradually increasing it from zero to a predetermined fixed value and then maintaining a given voltage on the reference resistor 22. In this case, the generator unit current 6 can generate at least four different values of the constant measuring current Iizm1, Iizm2, Iizm3, Iizm4 depending on the selected measurement limit. Thus, all measurements of unknown resistance will be performed at a constant measuring current, and stray capacitances and inductances will not affect the measurement results.

CPU 1 independently determines the steady-state constant current in time or the current generator transmits information about the steady-state measuring current in the circuit to CPU 1. CPU 1 selects the gain of the reference and measuring paths in accordance with the selected measurement limit and CPU 1 issues a command to the amplifier unit 4 of the measuring path to measure the zero offset of the amplifier at the selected gain.

The amplifier unit of the measuring path 4 connects its input with the help of a controlled switch 40 to the common bus 42 and generates an amplified output signal corresponding to the zero offset of the amplifier of the measuring path 4 at the selected gain and switches to the storage mode of the generated Uvx2 signal and transfers information to the CPU 1 completed operation.

The CPU 1 transmits a command to the processing unit 12 to the unit of the analog-to-digital converter 8 to measure the signal from the amplifier unit 4 of the measuring path. In the ADC block 8, the processor device 12 sets at its outputs an initial binary digital code supplied to the inputs of the digital-to-analog converter (DAC) 13, the reference input of which receives the reference voltage generated by the reference voltage source 15. The DAC 13 weakens the reference voltage with a degree of attenuation proportional to binary digital code from the processor device 12. The current signal from the DAC 13 is converted into a voltage signal in the Converter 14, the output signal of which is fed to the input of the adder 9 second enu ADC unit 8 which compensates Uvh2 signal corresponding attenuated in accordance with a digital code to the reference voltage, and outputs the resultant signal to the input of error amplifier 10, a second ADC circuit 8, which amplifies the difference signal between weak and Uvx2 Uref. From the output of error amplifier 10, the signal goes to comparator 11, where it is compared with the signal from common bus 42.

The processor device 12 enables the comparator 11 to operate from its control output D2 and receives the signal comparison result to its input B2. If the attenuated signal Uon in this case exceeds Uin2, the processor device 12 selects the next degree of attenuation of the signal Uon using a binary digital code and again receives the signal from the comparator 11. Thus, the processor device 12 selects by the method of successive approximation the exact measure of the signal Uin2 in terms of Uon. After the measurement of the signal Uvx2 is completed, the processor device 12 transmits the selected digital code to the CPU 1 and prohibits the operation of the comparator 11 so as not to interfere with the power supply circuits during the subsequent measurement of the signal along the channel of the reference path.

Then, the CPU 1 issues a command to the amplifier unit 7 of the reference path to measure the zero offset of the amplifier at the selected gain. The block of the amplifier 7 of the reference path connects its input using a managed switch 34 to a common bus 42 and generates an amplified output signal corresponding to a zero offset of the amplifier 7 of the reference path, while the amplifier 7 goes into storage mode of the signal Uin1 generated by it and transmits data about 1 performing an operation.

CPU 1 transmits to the ADC block 8 to the processor device 12 a command for measuring Uin1 from the block of the amplifier 7 of the reference path. The processor device 12 selects by the method of successive approximation a digital code, which is a measure of the signal Uin1 in terms of Uop. For this, the sequence of operations is repeated, as for Uin2, but already using the adder 9 of the first circuit, amplifier 10 and comparator 11 (first circuit), respectively. The processor device 12 enables the comparator 11 of the first circuit to operate from the control input and receives the result of comparing the signal Uin1 with a regulated attenuated reference voltage to its input. After the measurement of the signal Uin1 is completed, the processor device 12 transmits the selected digital code to the CPU 1 and prohibits the operation of the comparator 11 of the first circuit from the control input. This concludes the measurement of the zero offset of the reference path amplifier.

After completing the measurement of the zero offset of the amplifiers of the measuring and reference paths, the CPU 1 issues a command to the amplifier unit 4 of the measuring path to measure the voltage at an unknown resistance 30 at a selected gain. The amplifier unit 4 of the measuring path connects its input with the help of a controlled switch 40 to the potential terminal 41, and the input of the amplifier unit 4 receives a voltage that is established at an unknown resistance 30 with a constant measuring current flowing through it.

The resistance of the lead wires 31, 32 does not affect the measurement result, because there is no current in the potential circuit. The signal from the potential terminal 41 is amplified in the amplifier 4 of the measuring path at a selected gain, and the amplifier 4 of the measuring path switches to the storage mode of the generated signal Uin2 and transmits data to the CPU 1 about the generated signal.

The CPU 1 transmits a command to measure the signal Uin2 to the ADC unit 8 on the processor unit 12. The processor device 12 selects by the method of successive approximation a digital code, which is a measure of the signal Uin2 in terms of Uop. After the measurement of the signal Uin2 is completed, the processor device 12 transmits the selected digital code to the CPU 1. After that, the CPU 1 issues a command to the amplifier unit 7 of the reference path to measure the potential difference on the reference resistor 22 at a selected gain.

The block of the amplifier 7 of the reference path connects its input using a managed switch 34 to the output of the differential amplifier 33. The differential amplifier 33 receives at its inputs a signal from the potential terminals of the reference resistor 22, which is a voltage drop across the potential terminals of the reference resistor 22 and gives this output the same voltage drop formed relative to the common bus 42. The block of the amplifier of the reference path 7 generates at its output an amplified signal Uin1 corresponding to the amplified voltage drop voltage on the reference resistor 22 when flowing through it a measuring current Iizm. Then, the amplifier 7 of the reference path enters the storage mode of the generated signal Uin1 and transmits data about the completion of the operation to the CPU 1.

CPU 1 transmits to the ADC block 8 to the processor device 12 a command for measuring the signal Uin1 from the block of the amplifier 7 of the reference path. The processor device 12 selects by the method of successive approximation a digital code, which is a measure of the signal Uin1 in terms of Uop. After completing the measurement of the signal Uin1, the processor device 12 transmits the selected digital code to the CPU 1.

CPU1, taking the measured values Un1, Uin1, Uin2, Uin2, calculates the exact value of the measured resistance by the formula:

Rx = (Uin2-Unl2) * K1 * Ret / ((Uin1-Unl1) * K2),

Rx is the value of the unknown resistance;

Uin2 - voltage measured by an analog-to-digital converter unit at an unknown resistance;

Un2 - zero offset voltage of the amplifier of the measuring path at the selected gain K2;

K1 is the gain of the amplifier block of the reference path;

Ret is the resistance value of the reference resistor at a given operating temperature;

Uin1 is the voltage measured by an analog-to-digital converter unit on a reference resistor when a measuring current flows through it;

Unl1 - zero bias voltage of the amplifier of the reference path at the selected gain K1;

K2 is the gain of the amplifier unit of the measuring path.

The CPU 1 transmits to the keyboard and display controller 5 the calculated exact value of the measured resistance in digital form, which displays the received data on the display and makes them directly available for reading.

When the device is operating in automatic mode, the voltage drop across the reference resistor and the unknown resistance are pre-measured, the zero offset of the amplifiers of the reference and measuring paths with a gain equal to one, to determine the limit of measurement.

The measurement of the voltage drop across the reference resistor and the unknown resistance, zero offset of the amplifiers of the reference and measuring paths is carried out with a frequency of at least 1 kHz.

Implemented the proposed method (method 2) measuring the active resistances of the transformer windings using the proposed device as follows.

The central processing unit 1, using the temperature control unit 2, provides the necessary temperature inside the device, constantly monitoring it, and maintaining it in predetermined limits. The signal about the achievement of the operating temperature of the measuring circuit is transmitted to the CPU 1, which issues a command to the keyboard and display controller 5 and the latter displays the readiness of the device for measurements. The operator selects the mode (automatic or manual) and, if the manual mode is selected, selects the measurement limit of the unknown resistance 30 of the transformer winding, the controller 5 transfers this data to the CPU 1, which saves them and sends a command to the current generator unit 6 to generate the first specified measuring current in measuring circuit. At the same time, the current generator unit 6 generates a given measuring current in a circuit containing a reference resistor 22 and an unknown resistance 30 connected in series with it by gradually increasing it from zero to a predetermined fixed value and then maintaining a given voltage at the reference resistor 22. At the same time, the current generator block 6 can generate at least four different values of the constant measuring current — Ime1, Imeme2, Imeme3, Imeme4 depending on the selected measurement limit. Thus, all measurements of unknown resistance will be performed at a constant measuring current, and stray capacitances and inductances will not affect the measurement results.

The central processing unit 1 sends a command to the unit for preparing the measurement object 3, which gives the final sequence of voltage pulses of alternating polarity to the free winding of the measurement object (transformer) 46. One of the variants of the pulse train for preparing the measured winding is shown in Fig. 4 under letter a, which shows dependence of voltage from the output of the preparation unit of the measurement object in time. At the same time, measuring current Iism flows through an unknown resistance 30. Due to the phenomenon of induction, the pulse train from the preparation unit of the measurement object 3 enters the free winding 46 and causes a change in the magnetization of the transformer core, which contributes to the rapid establishment of a stable voltage at an unknown resistance 30 when Imess flows through it. A graph of the change in magnetization of the core of the transformer over time is shown in figure 4 under the letter b.

CPU 1 independently determines the steady-state constant current in time, or the current generator transmits information about the steady-state measuring current in the circuit to CPU 1. CPU 1 independently determines the time by which the training unit for the measurement object 3 outputs the pulse sequence, or the preparation unit of the measurement object transmits information about the end of the output the sequence of pulses in the CPU 1. CPU 1 selects the gain for the amplifier blocks of the reference and measuring paths in accordance with the selected limit Tests for the CPU 1 and instructs amplifier unit 4, the measuring path to conduct zero amplifier measuring offset at a selected amplification factor.

The amplifier unit of the measuring path 4 connects its input with the help of a controlled switch 40 to the common bus 42 and generates an amplified output signal corresponding to the zero offset of the amplifier of the measuring path 4 at the selected gain and switches to the storage mode of the generated Uvx2 signal and transfers information to the CPU 1 completed operation.

The CPU 1 transmits a command to the processing unit 12 to the unit of the analog-to-digital converter 8 to measure the signal from the amplifier unit 4 of the measuring path. In the ADC block 8, the processor device 12 sets at its outputs an initial binary digital code supplied to the outputs of the digital-to-analog converter (DAC) 13, the reference input of which receives the reference voltage generated by the reference voltage source 15. The DAC 13 weakens the reference voltage with a degree of attenuation proportional to the binary digital code from the processor device 12. The current signal from the DAC 13 is converted into a voltage signal in the Converter 14, the output signal of which is fed to the input of the adder 9 second ADC circuit block 8 which compensates Uvx2 signal corresponding attenuated in accordance with a digital code to the reference voltage, and outputs the resultant signal to the input of error amplifier 10, a second ADC circuit 8, which amplifies the difference signal between weak and Uvx2 Uref. From the output of error amplifier 10, the signal goes to comparator 11, where it is compared with the signal from common bus 42.

The processor device 12 enables the comparator 11 to operate from its control output D2 and receives the signal comparison result to its input B2. If the attenuated signal Uop in this case exceeds Uvx2, the processor device 12 selects the next degree of attenuation of the signal Uop using a binary digital code, and again receives the signal from the comparator 11. Thus, the processor device 12 selects by the method of successive approximation the exact measure of the signal Uв2 in Uon performance. After the measurement of the signal Uvx2 is completed, the processor device 12 transmits the selected digital code to the CPU 1 and prohibits the operation of the comparator 11 so as not to interfere with the power supply circuits during the subsequent measurement of the signal along the channel of the reference path.

Then, the CPU 1 issues a command to the amplifier unit 7 of the reference path to measure the zero offset of the amplifier at the selected gain. The block of the amplifier 7 of the reference path connects its input using a managed switch 34 to a common bus 42 and generates an amplified output signal corresponding to a zero offset of the amplifier 7 of the reference path, while the amplifier 7 goes into storage mode of the signal Uvx1 that it generates and transmits data about 1 performing an operation.

CPU 1 transmits to the ADC block 8 to the processor device 12 a command to measure Ux1 from the block of the amplifier 7 of the reference path. The processor device 12 selects by the method of successive approximation a digital code, which is a measure of the signal Uв1 in terms of Uon. For this, the sequence of operations is repeated as for Uвx2, but using the adder 9 of the first circuit, amplifier 10, and comparator 11 (first circuit), respectively. The processor device 12 permits the operation of the comparator 11 of the first circuit from the control input and receives the result of comparing the signal Uvx1 with an adjustable attenuated reference voltage to its input. After the measurement of the signal Uvx1 is completed, the processor device 12 transmits the selected digital code to the CPU 1 and prohibits the operation of the comparator 11 of the first circuit from the control input. This concludes the measurement of the zero offset of the reference path amplifier.

After completing the measurement of the zero bias of the amplifiers of the measuring and reference paths, the CPU 1 issues a command to the amplifier unit 4 of the measuring path to measure the voltage at the unknown resistance of the transformer winding 30 at a selected gain. The amplifier unit 4 of the measuring path connects its input with the help of a controlled switch 40 to the potential terminal 41, and the input of the amplifier unit 4 receives a voltage that is established at an unknown resistance 30 with a constant measuring current flowing through it. The resistance of the lead wires 31, 32 does not affect the measurement result, because there is no current in the potential circuit. The signal from the potential terminal 41 is amplified in the amplifier of the measuring path 4 at a selected gain, and the amplifier 4 of the measuring path switches to the storage mode of the Uvx2 signal generated by it, and transmits data to the CPU 1 about the generated signal.

The CPU 1 transmits a command to measure the signal Uvx2 to the ADC unit 8 on the processor device 12. The processor device 12 selects by a method of successive approximation a digital code, which is a measure of the signal Ux2 in terms of Uop. After the measurement of the signal Uvx2 is completed, the processor device 12 transmits the selected digital code to the CPU 1. After that, the CPU 1 issues a command to the amplifier unit 7 of the reference path to measure the potential difference on the reference resistor 22 at a selected gain.

The block of the amplifier 7 of the reference path connects its input using a managed switch 34 to the output of the differential amplifier 33. The differential amplifier 33 receives at its inputs a signal from the potential terminals of the reference resistor 22, which represents the voltage drop across the potential terminals of the reference resistor 22 and gives this output the same voltage drop formed relative to the common bus 42. The block of the amplifier of the reference path 7 generates at its output an amplified signal Uvx1 corresponding to the amplified voltage drop yazheniya on the reference resistor 22 when flowing through a measuring current Itest. Then the amplifier 7 of the reference path enters the storage mode of the generated signal Ux1 and transmits data about the operation to the CPU 1.

The CPU 1 transmits to the ADC block 8 to the processor device 12 a command to measure the signal Uvx1 from the block of the amplifier 7 of the reference path. The processor device 12 selects by the method of successive approximation a digital code, which is a measure of the signal Ux1 in terms of Uop. After the measurement of the signal Uvx1 is completed, the processor device 12 transmits the selected digital code to the CPU 1.

CPU1, taking the measured values Un1, Uin1, Uin2, Uin2, calculates the exact value of the measured resistance by the formula:

Rx = (Uin2-Unl2) * K1 * Ret / ((Uin1-Unl1) * K2),

Rx is the value of the unknown resistance;

Uin2 - voltage measured by an analog-to-digital converter unit at an unknown resistance Rx;

Un2 - zero offset voltage of the amplifier of the measuring path at the selected gain K2;

K1 is the gain of the amplifier block of the reference path;

Ret is the resistance value of the reference resistor at a given operating temperature;

Uin1 is the voltage measured by an analog-to-digital converter unit on a reference resistor when a measuring current flows through it;

Unl1 - zero bias voltage of the amplifier of the reference path at the selected gain K1;

K2 is the gain of the amplifier unit of the measuring path.

The CPU 1 transmits to the keyboard and display controller 5 the calculated exact value of the measured resistance in digital form, which displays the received data on the display and makes them directly available for reading.

The work of the measuring circuit as follows.

At the command of the CPU 1, the block of the current generator 6 sets the zero current in the measuring circuit, smoothly changing it from the initial value to zero, the unit for preparing the measurement object 3 issues a final pulse train to its terminals. On the free winding of the transformer 46, a voltage is generated in accordance with the pulse train of the measurement object. When this occurs, the magnetization of the core of the transformer changes, the magnetization is set, corresponding to a current equal to zero.

When the device operates in automatic mode, the final sequence of pulses of preparation of the measurement object is formed in such a way that the values of the products of the amplitude and duration of the pulses form an alternating series, the members of which decrease with increasing serial number, and the pauses between pulses do not exceed their duration.

When the device is in automatic mode, the preparation of the measurement object is carried out by forming a finite alternating sequence of voltage pulses, which is fed to the free winding of the measurement object. When the constant measuring current is set and the output of the pulse train of the preparation of the object is completed, a series of measurements of the voltage drop across the reference resistor and the unknown resistance is made, the zero offset of the amplifiers of the reference and measuring paths at the selected gain. According to the measurement results, it is determined whether a constant, unchanged in time voltage drop across an unknown resistance Rx is established. If the voltage drop varies over time, then the preparation of the measurement object is repeated, and the pulse train of the preparation of the measurement object is changed until a time-stable voltage drop at the unknown resistance Rx is achieved.

When the device is operating in automatic mode, the pulse train of the preparation of the measurement object is formed on one free transformer winding or several free transformer windings simultaneously.

Claims (23)

1. The method of measuring the active resistance, which consists in applying a first voltage to a circuit containing an unknown resistance connected in series with a reference resistor, for the total current to flow through them, form a reference voltage, form the product of the reference voltage and the selected number, change the value of the selected numbers in such a way as to bring the weakened reference voltage in line with the voltage drop at an unknown resistance, and use the selected number to indicate in unknown resistance characteristics, characterized in that they create and maintain the temperature inside the measuring device in predetermined limits, form a given measuring current in the measuring circuit by gradually increasing it from zero to a predetermined fixed value and then maintaining this value, select amplification factors for reference amplifiers and measuring paths, measure the zero bias of the amplifiers and measure the voltage drop across the reference resistor and unknown oprotivlenii respect generated reference voltage, the magnitude of unknown resistance is determined based on the value obtained for the voltage drop across the reference resistor and an unknown impedance, ZO amplifiers and the exact value of the reference resistor. 2. The method according to claim 1, characterized in that the value of the unknown resistance is determined by the formula: Rx = (Uvx2-Unl2) · K1 · Reth / ((Uvx1-Unl1) · K2), where Rx is the value of the unknown resistance; Uvx2 - voltage measured by an analog-to-digital converter unit at an unknown resistance; Un2 - zero offset voltage of the amplifier of the measuring path at the selected gain K2; K1 is the gain of the amplifier block of the reference path; Ret is the resistance value of the reference resistor at a given operating temperature; Uin1 is the voltage measured by an analog-to-digital converter unit on a reference resistor when a measuring current flows through it; Unl1 - zero bias voltage of the amplifier of the reference path at the selected gain K1; K2 is the gain of the amplifier unit of the measuring path. 3. The method according to claim 1, characterized in that the preliminary measure the value of the voltage drop across the reference resistor and the unknown resistance, the zero offset of the amplifiers of the reference and measuring paths with a gain equal to one to determine the limit of measurement. 4. The method according to claim 1, characterized in that all measurements are carried out with a frequency of at least 1 kHz. 5. The method of measuring the active resistance of the transformer winding, which consists in applying a first voltage to a circuit containing an unknown resistance connected in series with a reference resistor, for the total current to flow through them, form a reference voltage, form a product of the reference voltage and the selected number, change the value of the selected number so as to bring the weakened reference voltage in accordance with the voltage drop at an unknown resistance, and use selected the nth number for indicating the value of the unknown resistance, characterized in that they create and maintain the temperature inside the measuring device in predetermined limits, form the specified measuring current in the measuring circuit, by gradually increasing it from zero to a given fixed value, followed by maintaining this value, on one a sequence of impulses of preparation of the measured transformer winding is formed from the free windings of the transformer until a constant is established on the last th voltage drop, select the amplification factors for the amplifiers of the reference and measuring paths, measure the zero bias of the amplifiers, and measure the voltage drop on the reference resistor and the unknown resistance relative to the generated reference voltage, form a zero measuring current in the measuring circuit by smoothly decreasing from the set value to zero, on the free winding of the transformer form a sequence of pulses of preparation of the measured winding of the transformer for until the latter is not located on a negligible voltage drop, the value of the unknown resistance of the transformer winding being measured is determined based on the value obtained for the voltage drop across the reference resistor and an unknown impedance, ZO amplifiers and the exact value of the reference resistor. 6. The method according to claim 5, characterized in that the value of the unknown resistance is determined by the formula: Rx = (Uvx2-Unl2) * K1 * Ret / ((Uvx1-Unl1) * K2), where Rx is the value of the unknown resistance; Uvx2 - voltage measured by an analog-to-digital converter unit at an unknown resistance; Un2 - zero offset voltage of the amplifier of the measuring path at the selected gain K2; K1 is the gain of the amplifier block of the reference path; Ret is the resistance value of the reference resistor at a given operating temperature; Uvx1 is the voltage measured by the block of the analog-to-digital converter on the reference resistor when the measuring current flows through it; Unl1 - zero bias voltage of the amplifier of the reference path at the selected gain K1; K2 is the gain of the amplifier unit of the measuring path. 7. The method according to claim 5, characterized in that the sequence of pulses of the preparation of the measurement object is formed in such a way that the products of the amplitude and duration of the pulses comprise an alternating series whose members decrease with increasing their serial number, and the pauses between pulses do not exceed the pulse duration. 8. The method according to claim 5, characterized in that the shape of the pulse train of the preparation of the measurement object is changed until a time-stable voltage drop across the unknown resistance is achieved. 9. The method according to claim 5, characterized in that the pulse train of the preparation of the measurement object is formed on several free transformer windings simultaneously. 10. A device for determining active resistance, containing an unknown resistance and a reference resistor connected in series, a unit for generating a predetermined voltage in the measuring circuit, a programmable means for scaling the reference voltage, a comparator, indication means, characterized in that it is additionally equipped with a differential amplifier, blocks of reference amplifiers and measuring paths, the unit for preparing the measurement object, the temperature control unit, while the input-output of the central process the weed device is connected to the input-output of the keyboard and display control unit, temperature control unit, object preparation unit, reference and measuring path amplifier blocks, analog-to-digital converter unit containing two identical circuits, each of which consists of a series-connected adder, error amplifier , and a comparator, while the input-output of each comparator is connected to the input-output of the processor device, the digital outputs of which are connected to the corresponding inputs of the digital-analog the converter, the output of which is connected through the current / voltage converter to the inputs of the adders of both circuits, and the second input of the digital-to-analog converter is connected to the output of the reference voltage source, which is also connected to the inputs of the adders of both circuits, and the current generator block contains two generators, the output of the first generator connected to the current input of the first reference resistor, the potential terminals of which are connected to the control inputs of the first generator, one of the outputs of the second generator is connected to the current in by the water of the second reference resistor through an unknown resistance, the potential terminals of the second reference resistor are connected to the inputs of the second current generator and to the inputs of the differential amplifier connected to the amplifier of the reference path, the output of which is connected to the input of the adder of the first circuit of the analog-to-digital converter unit, and one of the conclusions of the unknown the resistance is connected to the input of the amplifier unit of the measuring path, while the second output of the unknown resistance is connected to a common bus. 11. The device according to claim 10, characterized in that the current generator is configured to control the magnitude of the current flowing through an unknown resistance, providing the required current parameters. 12. The device according to claim 10, characterized in that the current generator is made with the possibility of smooth adjustment of the measuring current in accordance with the voltage measured at an unknown resistance. 13. The device according to claim 10, characterized in that the current generator is configured to generate at least four measuring constant currents and the ability to smoothly increase the current from zero to the desired value and decrease from a fixed value to zero. 14. The device according to claim 10, characterized in that the current generator is configured to use at least two generators using respectively two reference resistors, with the ability to control the voltage across the reference resistors. 15. The device according to claim 10, characterized in that the current generator is configured to generate zero current through one of the current generators and generate current from zero to a predetermined value through the second generator. 16. The device according to claim 10, characterized in that the current generator is configured to use a capacitive discharge to create a short-term current of large magnitude, the value of which can be kept constant for a period of time necessary for measurement. 17. The device according to claim 10, characterized in that the current generator is configured to generate current in the forward and reverse direction to account for the thermopower. 18. The device according to claim 10, characterized in that the current generator is configured to connect to the current and potential terminals of the device and issue an adjustable current through any pair of lead wires to ensure reliable connection. 19. The device according to claim 10, characterized in that the unit for preparing the measurement object is configured to generate an alternating sequence of pulses of a given shape, and the pauses between pulses do not exceed the pulse duration. 20. The device according to claim 10, characterized in that the unit for preparing the measurement object is configured to generate a sequence of pulses during the generation of a smoothly increasing or decreasing current by the current generator and the ability to adjust and change the mode depending on the magnitude of the current and the current generator operating mode. 21. The device according to claim 10, characterized in that the unit for preparing the measurement object is configured to adjust and change the shape of the sequence of issued pulses depending on the measurement result. 22. The device according to claim 10, characterized in that the unit for preparing the measurement object is configured to control the current flowing through the free winding of the object (transformer). 23. The device according to claim 10, characterized in that the unit for preparing the measurement object is configured to connect to several free transformer windings simultaneously with the formation for each of them of a given sequence of voltage pulses of alternating polarity.

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