Resistance measuring circuit and resistance measuring equipment

Abstract

The present invention discloses a resistance measurement circuit and a resistance measurement device, wherein the resistance measurement circuit includes: a data acquisition module, having a connection terminal of a resistance to be measured, a connection terminal of a reference resistance, and a data signal output terminal, for collecting the current or voltage of the resistance to be measured and the reference resistance, the connection terminal of the resistance to be measured and the connection terminal of the reference resistance are electrically isolated from the output terminal; the input terminal, the output terminal, and the power supply are isolated from each other. A measurement module is connected to the data signal output terminal, and is used to measure the current or voltage output by the data signal output terminal to measure the resistance value of the resistance to be measured. Since data acquisition and data measurement are electrically isolated, different voltages or currents can be applied, and different voltages or currents can be output at the same time, and a reference point can be selected according to the physical and mathematical definition of the resistance, reducing differential mode interference, common mode interference, and noise interference, which greatly facilitates resistance measurement, expands the measurement range, and can also effectively reduce measurement errors and improve measurement accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic measurement, and in particular to a resistance measuring circuit and a resistance measuring device. Background Art

[0002] Resistor is an energy-consuming element that hinders the flow of current. For example, light bulbs and electric heaters can use resistors as their circuit models. According to Ohm's law, the current I flowing through the resistor is proportional to the voltage U across the resistor.

[0003] Almost all electrical equipment has resistance elements. Even if there is no special resistor, the conductor is also an equivalent resistor, so resistance measuring instruments are widely used. Single-arm bridge for measuring resistance value, double-arm bridge for measuring small resistance, insulation resistance meter (megohmmeter) for measuring insulation resistance, ground resistance meter (ground resistance meter) for measuring ground resistance, resistance meter, milliohmmeter, microohmmeter, resistivity meter, insulation resistance monitor and multimeter are all instruments for measuring resistance. In fact, many electrical measuring instruments have resistance measurement function. Resistance measurement is required in many scenarios.

[0004] However, in actual measurements, when the above-mentioned instruments are used for measurement, there is usually an inaccurate resistance measurement phenomenon, which in turn affects the subsequent work.

[0005] Therefore, how to accurately measure resistance becomes a technical problem that needs to be solved urgently. Summary of the invention

[0006] To this end, according to the first aspect, an example of the present invention provides a resistance measurement circuit, including: a data acquisition module, having a connection terminal of a resistor to be measured, a reference resistor connection terminal and a data signal output terminal, for collecting current data or voltage data of the resistor to be measured and the reference resistor, the connection terminal of the resistor to be measured and the reference resistor connection terminal being electrically isolated from the data signal output terminal; a measurement module, connected to the data signal output terminal, for measuring the current data or voltage data output by the data signal output terminal, so as to measure the resistance value of the resistor to be measured.

[0007] Optionally, the data acquisition module includes: a first isolation amplifier having a first input terminal for connecting to a resistor to be measured and a first output terminal isolated from the first input terminal; a second isolation amplifier having a second input terminal for connecting to a reference resistor and a second output terminal isolated from the second input terminal; the first output terminal and the second output terminal are isolated or share a common ground; the measurement module is arranged between the first output terminal and the second output terminal, and is used to collect the current difference or voltage difference between the first output terminal and the second output terminal, as well as the voltage and current output by the first output terminal or the voltage or current output by the second output terminal.

[0008] Optionally, the resistance measurement circuit also includes a power supply module for providing current or voltage; the first input terminal of the first isolation amplification module is used to be connected to one end of the resistor to be measured, and one end of the power supply module is used to be connected to the other end of the resistor to be measured; the first isolation amplification module also includes a third input terminal, and the third input terminal is connected to the other end of the power supply module; the second input terminal of the second isolation amplification module is used to be connected to one end of the reference resistor, and one end of the power supply module is used to be connected to the other end of the reference resistor; the second isolation amplification module also includes a fourth input terminal, and the fourth input terminal is connected to the other end of the power supply module.

[0009] Optionally, the measurement module comprises a current measurement unit, configured to measure a current difference between the first output terminal and the second output terminal, and a current output by the first output terminal and a current output by the second output terminal.

[0010] Optionally, the resistance measurement circuit also includes a power supply module for providing current or voltage; the first isolation amplification module also includes a third input terminal, the first input terminal of the first isolation amplification module is used to connect to one end of the resistor to be measured, and the third input terminal is used to connect to the other end of the resistor to be measured; the second isolation amplification module also includes a fourth input terminal, the second input terminal of the second isolation amplification module is used to connect to one end of the reference resistor, and the fourth input terminal is used to connect to the other end of the reference resistor.

[0011] Optionally, the third input terminal is connected to the second input terminal; one end of the power module is connected to the first input terminal, and the other end of the power module is connected to the fourth input terminal.

[0012] Optionally, the measurement module includes a voltage measurement unit, which is used to measure the voltage output by the first output terminal and the voltage output by the second output terminal, and the voltage difference between the first output terminal and the second output terminal. Optionally, the resistance measurement circuit also includes: a data processing module, which is connected to the measurement module and is used to obtain the resistance value of the resistor to be measured according to the measured voltage difference or current difference.

[0013] According to a second aspect, an embodiment of the present invention provides a resistance measuring device, comprising: a device body; and a resistance measuring circuit as described in any one of the first aspects above.

[0014] The resistance measurement circuit and resistance measurement device provided by the embodiment of the present invention include a data acquisition module, which has a connection terminal of a resistance to be measured, a connection terminal of a reference resistance, and a data signal output terminal, and is used to collect current data or voltage data of the resistance to be measured and the reference resistance, and the connection terminal of the resistance to be measured and the connection terminal of the reference resistance are electrically isolated from the data signal output terminal; a measurement module is connected to the data signal output terminal, and is used to measure the current data or voltage data output by the data signal output terminal to measure the resistance value of the resistance to be measured. Since data acquisition and data measurement are electrically isolated, different voltages or currents can be applied, and different voltages or currents can be output at the same time, and the reference point can be selected according to the physical and mathematical definition of the resistance, which greatly facilitates the resistance measurement, expands the measurement range, and can effectively reduce the measurement error and improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is the external connection method of measuring resistance by the prior art voltammetry;

[0017] Figure 2 It is the existing technology voltammetry method for measuring resistance internal connection;

[0018] Figure 3 The prior art method of measuring resistance using a resistance box and an ammeter;

[0019] Figure 4 The prior art method of measuring resistance using a resistance box and a voltmeter;

[0020] Figure 5 It is the principle circuit of measuring resistance by using a single-arm bridge using the zero value method in the prior art;

[0021] Figure 6 It is the principle circuit of measuring resistance with a double-arm bridge using the zero-value method in the prior art;

[0022] Figure 7 is a schematic diagram of a resistance measurement circuit of the present invention;

[0023] Figure 8 is a schematic diagram of another resistance measurement circuit of the present invention;

[0024] Fig. 9 is a schematic diagram of another resistance measurement circuit of the present invention;

[0025] Fig.10 The front panel of the resistance measuring device of the present invention;

[0026] Fig.11 This is the rear panel of the resistance measuring device of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the process of measuring resistance in practice, inaccurate measurement is often encountered. The applicant has conducted in-depth research on existing measurement methods and found that the existing measurement methods all have certain measurement errors, resulting in inaccurate measurement. The existing measurement methods are generally the following:

[0029] The classic method for measuring resistance is the volt-ampere method, which is based on Ohm's law for partial circuits and Ohm's law for closed circuits.

[0030] The resistance measured by the volt-ampere method is determined based on formula (2).

[0031] R=U / I (2)

[0032] Where: R is the resistance of the resistor being measured; U is the voltage value measured by the voltmeter; I is the current value measured by the ammeter.

[0033] Due to the voltage and current division of the internal resistance of the voltmeter and ammeter, measurement errors occur. Therefore, the volt-ampere method is divided into the internal connection method and the external connection method. Figure 1 As shown in the figure, it can be seen that the ammeter is connected to the outside of the connection between the measured resistance and the voltmeter. The error generated by this measurement method is shown in formula (3):

[0034]

[0035] From the above formula, we can see that the measurement error is caused by the internal resistance shunt of the voltmeter, so only when E V >>R x The volt-ampere method with an external ammeter is used only when Figure 2 As shown in the figure, the ammeter is connected to the inner side of the connection between the resistor to be tested and the voltmeter. The error generated by this measurement method is shown in formula (4).

[0036]

[0037] From the above formula, we can see that the reason for the measurement error is the voltage division of the ammeter, so only when R x >>R A The volt-ampere method with an internal ammeter is used.

[0038] Substitution method: When measuring resistance using the volt-ampere method, whether the ammeter is connected internally or externally, it will cause errors in the measurement. Using the comparison method to measure resistance can reduce these errors. During the test, first connect a resistor to be measured, write down the reading of the ammeter in the circuit, then replace the resistor to be measured with a resistance box, adjust the resistance box so that the reading of the ammeter in the circuit is the same as the original reading, so that the resistance value of the resistance box is the resistance value of the resistor to be measured. The substitution method can be divided into two types: using an ammeter to measure and using a voltmeter to measure. The wiring for measuring with a voltmeter is as follows: Figure 3 As shown, the S1 switch in the figure is used to switch the resistance to be measured and the reference resistance R N As in the resistor box, the S2 switch is used to switch the power supply so as to switch the resistance R to be tested. X and reference resistor R N A is an ammeter, which is used to measure current. The wiring for measuring with a voltmeter is as follows Figure 4 As shown in the figure, except that the voltmeter V is used instead of the ammeter A, everything else is the same. The substitution method is to first connect the resistor to be measured, write down the reading of the ammeter in the circuit, and then replace the resistor to be measured with a resistance box, adjust the resistance box so that the reading of the ammeter in the circuit is the same as the original reading, so that the resistance value of the resistance box is the resistance value of the resistor to be measured. In this way, the measurement of the resistor to be measured and the resistance box cannot be carried out at the same time, which will increase the measurement error due to changes in the power supply and changes in the measurement adjustment.

[0039] Zero value method: Connect the resistance to be measured and the reference resistance such as the resistance box to the detection circuit at the same time. By adjusting the size of the reference resistance, the zeroing instrument is made to point to zero. At this time, the value of the unknown resistance to be measured is equal to the value of the standard resistance. The measurement accuracy of this measurement method mainly depends on the accuracy of the standard resistance and the sensitivity of the zeroing instrument. Neither the internal impedance of the power supply nor the internal impedance of the zeroing instrument will affect the measurement result. The most typical method to measure resistance is to use a bridge, which is also a common method for precise measurement of resistance. The bridge is divided into a single bridge and a double bridge. The single bridge is also called a Wheatstone bridge. Its working principle is shown in Figure 5. Its bridge consists of an unknown resistance to be measured R1 and adjustable known resistances R2, R3 and R4. The four vertices a, b, c, and d in the figure are called bridge tops. I1, I2, I3, and I4 are the currents flowing through each bridge arm. R2 and R4 are composed of several convertible fixed resistors. R2 / R3 can be adjusted to form several different fixed ratios. Therefore, R2 and R4 are called proportional arms, or range converters. Selecting different proportional arms means selecting different ranges. R3 is a variable resistor made of multiple disks, called a measuring disk. G is a zero pointer, also called a galvanometer. Its function is to detect whether there is current at points b and d, and adjust the bridge until the zero pointer indicates zero, which is the zero value method. The balance condition and balance formula of a single bridge: When I1, I2, I3, and I4 are arbitrary values, there is current flowing in each branch, and there is also current I in the galvanometer. g . Adjusting I2, I3, and I4 can make I g =0, the bridge is in a balanced state. Bridge balance means that the potentials of points b and d are the same, I g =0, so, I1=I2, I3=I4, U ab =U ad ,U bc =U dc . From this we can see that I1R1=I3R3, I2R2=I4R4, and by dividing the two equations, we get

[0040] but

[0041] Therefore, we can get:

[0042] It can be seen from formula (6) that after adjusting the resistance to make the bridge balanced, the resistance to be measured R X ( Figure 5 The resistance R1 can be calculated from the readout values ​​of the three bridge arms of the bridge. This is the working principle of the bridge. Formula (5) is called the bridge balance condition, and the balance formula is: R1R4 = R2R3, that is, the product of the two bridge arms is equal. This leads to a property of the balanced bridge: the balance condition of the bridge is determined only by the relationship between the parameters of the bridge arms, and has nothing to do with the power supply voltage and the internal resistance of the zeroing instrument.

[0043] Characteristics and uses of a single bridge: When using a single bridge to measure resistance, when the measured resistance is less than 10Ω, the lead resistance and the contact resistance at the connection with the bridge cannot be ignored. If the lead resistance and contact resistance are large, the measurement result will have a large error.

[0044] The double bridge is specially used to measure small resistance. If you need to measure small resistance, such as the resistance of motor or transformer winding, shunt resistance, you cannot use a single bridge, but a double bridge, because the double bridge can eliminate the error caused by the lead wire. The working principle of the double bridge is as follows Figure 6 As shown, R x is the resistance to be measured, R N is the reference resistor, R N and R x All use four-terminal wiring and connect to the corresponding terminals of the double bridge. N and R x The connecting line r between them is called the cross line. R3 and R3′ are two adjustable bridge arms linked together, both of which are composed of multiple measuring disks. R3 is called the outer comparison arm, R3′ is called the inner comparison arm, R4 and R4′ are proportional arms, R4 is called the outer comparison arm, and R4′ is called the inner comparison arm. They should be set to the same value. N and R x After connection, adjust R3 and R3′ to make the galvanometer zero, and then calculate R x The value of is calculated as formula (7).

[0045]

[0046] The balance conditions and balance formulas of the double bridge are similar to those of the single bridge and will not be repeated here.

[0047] Characteristics and uses of double bridge:

[0048] The double bridge includes the current leads of the standard resistor and the resistor under test in the working power supply circuit and does not participate in the balance. In addition, the potential leads of both are included in each bridge arm. Since the resistance of each bridge arm has a large resistance value during the measurement process, the influence of the potential lead resistance can be ignored. From formula (7), it can be concluded that the indication error of the double bridge is related to the standard resistor R N In addition, it is mainly determined by the adjustment error of R3 and R4 and the cross-line resistance value r. Since it is actually very difficult to adjust R3 = R3' and R4 = R4', r cannot be absolutely zero (it is specified in the design to be below 0.01Ω), so the measurement accuracy of the double bridge is generally not high. In order to improve the sensitivity of the bridge galvanometer, the working power supply of the bridge must be increased, but if the working voltage is too high, the temperature of the resistor will increase, affecting the stability of the resistor.

[0049] Therefore, the applicant proposed a resistance measurement circuit. Figure 7As shown, the resistance measurement circuit may include: a data acquisition module 10 having a resistance to be measured R X Connection terminal 11, reference resistor R N The connection terminal 12 and the data signal output terminal 13 are used to collect the measured resistance R X and the reference resistor R N The current data or voltage data, the resistance to be measured R X Connect terminal 11 and the reference resistor R N The connection terminal 12 is electrically isolated from the data signal output terminal 13; the measuring module 20 is connected to the data signal output terminal 13 and is used to measure the current data or voltage data output by the data signal output terminal 13 to measure the resistance R to be measured. X resistance value.

[0050] Data acquisition and data measurement can be electrically isolated and different voltages or currents can be applied and output at the same time. In addition, the reference point can be selected according to the physical and mathematical definition of resistance, which greatly facilitates resistance measurement, expands the measurement range, effectively reduces measurement errors, and improves measurement accuracy.

[0051] In an optional embodiment, the data acquisition module 10 includes: a first isolation amplifier U1 having a function for connecting to the resistance to be measured R X A first input terminal and a first output terminal isolated from the first input terminal; a second isolation amplifier U2 having a first resistor R N a second input terminal and a second output terminal isolated from the second input terminal; the first output terminal is isolated from the second output terminal, but can be connected to a common ground through a wire as needed; a measuring module 20 is arranged between the first output terminal and the second output terminal, and is used to collect the voltage and current output by the first output terminal and the voltage or current output by the second output terminal, as well as the current difference or voltage difference between the two.

[0052] In this embodiment, the resistance measurement circuit can use the differential current method to measure the resistance, and can also use the differential pressure method to measure the resistance. X and reference resistor R N Provide power to collect the resistance R to be measured X and reference resistor R N Current data or voltage data.

[0053] Specifically, Figure 8 As shown, the differential current method can be measured using the following circuit, where the first input terminal of the first isolation amplifier module is used to connect to the resistor to be measured R X One end of the power module is connected to the resistance R to be measured. XThe first isolation amplifier module also includes a third input terminal, and the third input terminal is connected to the other end of the power module; the second input terminal of the second isolation amplifier module is used to connect to the reference resistor R N One end of the power module is connected to the reference resistor R N The second isolation amplifier module further comprises a fourth input terminal, and the fourth input terminal is connected to the other end of the power supply module. The measurement module comprises a current measurement unit, which is used to measure the current output by the first output terminal and the current output by the second output terminal, and the current difference between the currents of the two.

[0054] Specifically, Fig. 9 As shown, the differential pressure method can be measured using the following circuit, the first isolation amplifier module also includes a third input terminal, the first input terminal of the first isolation amplifier module is used to connect to the resistance R to be measured X The third input terminal is connected to the resistor R X The second isolation amplification module also includes a fourth input terminal, and the second input terminal of the second isolation amplification module is used to connect to the reference resistor R N The fourth input terminal is connected to the reference resistor R N The other end of the first output terminal is connected to the other end of the second output terminal; the third input terminal is connected to the second input terminal; one end of the power module is connected to the first input terminal, and the other end of the power module is connected to the fourth input terminal. The measurement module includes a voltage measurement unit, which is used to measure the voltage output by the first output terminal and the voltage output by the second output terminal, and the voltage difference between them.

[0055] The input circuit, output circuit, power supply circuit and ground of the isolation amplifier in the above-mentioned differential current method circuit and differential voltage method circuit are completely isolated, which can effectively reduce DC offset, current leakage and zero drift, reduce zero error, and directly reduce measurement error. Since the input impedance and output impedance have a great influence on the measurement, the input impedance and output impedance can be designed as needed, the input impedance of the voltage is large, and the input impedance of the current is small, which is conducive to reducing the measurement error. Furthermore, the use of complete isolation of the input circuit, output circuit, power supply circuit and ground can also effectively reduce differential mode interference and common mode interference, and improve measurement accuracy.

[0056] As an optional embodiment, a data processing module is connected to the measuring module and is used to obtain the resistance R to be measured according to the measured voltage difference or current difference. XIn this embodiment, the so-called data processing module may include: A / D converter, data acquisition card and other measurement parts and any one of a single-chip microcomputer, embedded AM, tablet computer or computer. In this embodiment, it is not limited to the above data processing modules. As long as the corresponding resistance can be calculated according to the corresponding current or voltage, it is within the protection scope of this embodiment.

[0057] Next, the beneficial effects of the resistance measuring circuit in this embodiment are described in detail in combination with the resistance measuring method in the prior art.

[0058] Compared with the volt-ampere method, the resistance measurement circuit in this embodiment avoids the measurement error caused by the internal resistance of the ammeter and voltmeter. It can be seen from the above (2), formula (3), and formula (4) that the ammeter is connected internally. Figure 2 Or external specific reference Figure 1 , will bring about measurement errors. The method of the present invention, the reference resistor R N With the resistance to be measured R X In series, the currents in the series circuit are equal and there is no need to measure the current. Therefore, the influence of the internal resistance of the ammeter can be completely eliminated. The reference resistance R N With the resistance to be measured R X They are connected in series to isolation amplifiers, whose input impedances are almost equal. The influence of input impedance can be ignored, and the resistance value of the resistor can be measured more accurately.

[0059] The resistance measurement circuit in this embodiment is compared with the substitution method: the substitution method is to first connect the resistance to be measured R X , record the reading of the ammeter in the circuit, and then X Replace it with a resistance box and adjust the resistance box so that the reading of the ammeter in the circuit is consistent with the original reading. In this way, the resistance value of the resistance box is the resistance to be measured R X However, the resistance to be measured R X The measurement with the resistance box cannot be performed at the same time, which will increase the measurement error due to the change of power supply and measurement adjustment. N With the resistance to be measured R X Simultaneous measurement can avoid the increase of measurement error caused by the change of power supply and measurement adjustment in the substitution method. In addition, the substitution method in the prior art has two zero errors, while the resistance measurement circuit in the present application uses an isolation amplifier, and the input and output are completely isolated from the power supply, and there is almost no zero error.

[0060] The resistance measurement circuit in this embodiment is compared with the zero value method. The zero value method is to compare the resistance to be measured RX with the reference resistance R N At the same time, it is connected to the detection circuit, and the reference resistance R is adjusted. N The value of the zero-pointing instrument is zero. At this time, the resistance to be measured RX is equal to the reference resistance R N The zero value method refers to the zero value that the sensitivity of the zero meter can indicate. If the sensitivity is 1×10 -5 The zeroing instrument has been zeroed. When the sensitivity is 1×10 -7 When the zeroing instrument is used, the instrument with higher sensitivity may point to non-zero. Since the zero value is relative, it is only relative to the sensitivity of a certain zeroing instrument. The measurement accuracy of the zeroing method mainly depends on the accuracy of the standard resistor and the sensitivity of the zeroing instrument.

[0061] The most typical circuit for measuring resistance using the zero value method is the bridge, which is divided into single bridge and double bridge. Its working principle is as follows: Figure 5 As shown, the calculation is as shown in formula (6). From formula (6), it can be seen that after adjusting the resistance to make the bridge balanced, the resistance to be measured R X , can be obtained from the readout values ​​of the three bridge arms of the bridge. This is the working principle of the bridge. Formula (5) is called the bridge balance condition, and the balance formula is expressed as: R1R4 = R2R3, that is, the product of the two bridge arms is equal. Thus, a property of the balanced bridge is obtained: the balance condition of the bridge is determined only by the relationship between the parameters of the bridge arms, and has nothing to do with the power supply voltage and the internal resistance of the zeroing instrument.

[0062] When using a single bridge to measure resistance, when the measured resistance is less than 10Ω, the lead resistance and the contact resistance at the bridge connection cannot be ignored. If the lead resistance and contact resistance are large, the measurement result will have a large error. The bridge balance condition is that the zero indicator points to zero. In order to accurately judge the balance, a highly sensitive zero indicator should be used. The bridge sensitivity is related to the bridge voltage. The higher the power supply voltage, the higher the sensitivity.

[0063] The double bridge can eliminate the error caused by the lead wire. The double bridge is specially used to measure small resistance. Figure 6 As shown, the calculation formula is formula (7). The double bridge includes the current leads of the standard resistor and the resistor under test in the working power supply circuit and does not participate in the balance. Moreover, the potential leads of both are included in each bridge arm. Since the resistance of each bridge arm has a large resistance value during the measurement process, the influence of the potential lead resistance can be ignored. From formula (7), it can be concluded that the indication error of the double bridge is related to the reference resistance R N In addition, it is mainly determined by the adjustment error of R3 and R4 and the cross-line resistance value r. Since it is actually very difficult to adjust R3 = R3' and R4 = R4', and r cannot be absolutely zero, the measurement accuracy of the double bridge is generally not high.

[0064] The resistance measurement circuit in this embodiment overcomes the influence of the lead resistance and contact resistance of the single bridge on the measurement result because the isolation amplifier has a high input impedance. Since the input and output circuits of the power amplifier are completely isolated, the output voltage is increased to improve the sensitivity, and the input is not increased, which will not increase the power of the resistor in the circuit. Therefore, the isolation of the isolation amplifier also solves the contradiction that the voltage needs to be increased in order to improve the sensitivity of the single bridge, but the increased voltage makes the power of the resistor unbearable. The synchronous adjustment resistors R3, R3' and R4, R4' and the cross-line resistance value r are removed from the resistance measurement circuit in this embodiment. Therefore, the defects of the double bridge are effectively overcome.

[0065] An embodiment of the present invention provides a resistance measuring device, which may include: a device body; and a resistance measuring circuit as described in any one of the above embodiments. In this embodiment, the device body may be a chassis of the resistance measuring device. Fig.10The front panel of the chassis of the resistance measuring device is shown as an example. The upper and middle parts of the left side are adjustable power supplies, and the upper part is an ammeter and a voltmeter, which are used to indicate the current and voltage of the voltage output. Below the ammeter, on the left is a current output key switch, and when it is installed, the current is output. Of course, other switches, such as toggle switches, rotary switches, button switches, etc., can also be used. Relays can also be used as long as the output and stop of the power supply can be controlled. To the right of the current output key switch is an indicator light. When the power supply has current output, the light is on, and when the current of the power supply stops outputting, the light goes out. Below the current output key switch and the indicator light are the current coarse adjustment knob and the current fine adjustment knob, which are used to adjust the size of the power supply output current. At present, many adjustable power supplies are digital program-controlled power supplies. Some use numeric keys, and some use up and down keys. As long as the corresponding functions can be realized, they are all OK. Below the voltmeter, on the left is a voltage output key switch, and when it is installed, the voltage is output. Of course, other switches, such as toggle switches, rotary switches, button switches, etc., can also be used. Relays can also be used as long as the output and stop of the power supply can be controlled. To the right of the current output key switch is an indicator light. When the power supply has voltage output, the light is on, and when the power supply stops outputting voltage, the light goes out. Below the voltage output key switch and indicator light are the voltage coarse adjustment knob and the voltage fine adjustment knob, which are used to adjust the output voltage of the power supply. At present, many adjustable power supplies are digital programmable power supplies. Some use numeric keys, and some use up and down keys. As long as the corresponding functions can be achieved, they are all acceptable. Below the left side, from left to right are the power switch, power indicator light, power output high end, ground, and power output low end. The power switch is used to connect or disconnect the power supply of the adjustable power supply. When the power indicator light is on, it means that the power supply of the adjustable power supply is turned on. When the power indicator light is off, it means that the power supply of the adjustable power supply is disconnected. The display screen is located above the middle and right parts of the panel. The LCD screen can display various parameters, such as the applied current, voltage, measured differential current, differential pressure, measured resistance and other parameters. This is just the display unit, which can be displayed with an LCD window, an LED display, or a pointer instrument display; desktop computers, tablet computers, laptops or other display devices can also be used as long as they can correctly display the relevant data. The signal waveform can also be displayed. For the display of the waveform, a liquid crystal display, an oscilloscope display, a desktop computer, a tablet computer, a laptop or other display device can be used, as long as the relevant waveform can be displayed correctly.Below the display screen is the adjustment switch for the reference resistor or standard resistor, which is an 11-bit decimal conversion switch connected in series. Five of them are drawn in the figure. Their function is to adjust the resistance value of the reference resistor or standard resistor so that the resistance value of the reference resistor or standard resistor in the circuit is close to the resistance value of the unknown resistor to be measured. Since the difference measurement range of the present invention is very large, the range of resistance difference between different reference resistors or standard resistors can also be set according to different measurement accuracy. Therefore, the number of switches can be increased or decreased. The functions of these switches are the same as those of the resistor box, so other switch devices can also be used, such as relays, pushbutton switches, resistor networks, etc. Below the adjustment switch is the resistor input terminal, which uses a four-terminal input. If the measurement accuracy is low, a two-terminal input can also be used. The input terminal on the left is the input terminal of the unknown resistor to be tested, R. XL1 and RXL2 is the current input terminal, R XP1 and R XP2 The right input terminal is the input terminal of the reference or standard resistor, R NL1 and R NL2 is the current input terminal, R NP1 and R NP2 It is the voltage input terminal. It is used to connect the reference or standard resistor. When the internal reference or standard resistor is empty, you can use the external reference or standard resistor. These reference or standard resistors can be traceable or calibrated, so that higher precision measurement can be achieved, and standard resistors can also be verified. Fig.11 It is the rear panel. The upper left is a power socket or fuse. Other forms can also be used, such as a power socket with a fuse. The lower left is the grounding knob. Be sure to set up a reliable grounding device in accordance with the grounding regulations. The lower right is the communication interface. There are USB, RJ45, RS232, etc. that can be set as needed. As long as it can meet the communication requirements, it will be fine. Use the differential method with an isolation amplifier to measure resistance. There can be two forms: the differential method is the differential current method, which is to measure resistance by measuring differential current, and the differential voltage method, which is to measure resistance by measuring differential voltage. The measurement principles of these two methods are the same, but the measured signal types are different, and the measurement results are all resistance.

[0066] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A resistance measuring circuit, characterized in that: The resistance measurement circuit can use a differential current method to measure the resistance to be measured, or can use a differential voltage method to measure the resistance to be measured. The resistance measurement circuit includes: A data acquisition module, comprising a resistance connection terminal to be measured, a reference resistance connection terminal and a data signal output terminal, for collecting current data or voltage data of the resistance to be measured and the reference resistance, wherein the resistance connection terminal to be measured and the reference resistance connection terminal are electrically isolated from the data signal output terminal; and the input terminal, the output terminal and the power supply are isolated from each other; A measuring module, connected to the data signal output terminal, and used to measure the current data or voltage data output by the data signal output terminal, so as to measure the resistance value of the resistor to be measured; A power module for providing current or voltage; The data acquisition module comprises: A first isolation amplifier having a first input terminal connected to the resistor to be measured and a first output terminal isolated from the first input terminal; A second isolation amplifier having a second input terminal for connecting the reference resistor and a second output terminal isolated from the second input terminal; the first output terminal and the second output terminal are isolated or share a common ground; The measuring module is connected to the first output terminal and the second output terminal respectively, and is used to measure the current difference or voltage difference between the first output terminal and the second output terminal, and the voltage or current output by the first output terminal and the voltage or current output by the second output terminal; wherein, The first input terminal of the first isolation amplifier is used to be connected to one end of the resistor to be measured, and one end of the power supply module is used to be connected to the other end of the resistor to be measured; The first isolation amplifier further includes a third input terminal, and the third input terminal is connected to the other end of the power module; The second input terminal of the second isolation amplifier is used to be connected to one end of the reference resistor, and one end of the power module is used to be connected to the other end of the reference resistor; or The first input terminal of the first isolation amplifier is used to connect to one end of the resistor to be measured, and the third input terminal is used to connect to the other end of the resistor to be measured; The second input terminal of the second isolation amplifier is used to be connected to one end of the reference resistor.

2. The resistance measuring circuit according to claim 1, characterized in that: When the resistance is measured by the differential current method, the measurement module includes a current measurement unit for measuring the current difference between the first output terminal and the second output terminal, and the current output by the first output terminal and the current output by the second output terminal.

3. The resistance measuring circuit according to claim 1, characterized in that: When the resistance is measured by the differential pressure method, the second isolation amplifier further includes a fourth input terminal; The third input terminal is connected to the second input terminal; One end of the power module is connected to the first input end, and the other end of the power module is connected to the fourth input end.

4. The resistance measuring circuit according to claim 1 or 3, characterized in that: When the resistance is measured by the differential pressure method, the measuring module includes a voltage measuring unit for measuring the voltage output by the first output terminal and the voltage output by the second output terminal, and the voltage difference between the first output terminal and the second output terminal.

5. The resistance measuring circuit according to claim 1, wherein: Also includes: The data processing module is connected to the measuring module and is used to obtain the resistance value of the resistor to be measured according to the measured voltage difference or current difference.

6. A resistance measuring device, characterized in that: include: Equipment body; as well as, A resistance measuring circuit as claimed in any one of claims 1 to 5.

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