Resistance measurement circuit and resistance measurement method thereof

Abstract

The present invention discloses a resistance measuring circuit and a resistance measuring method thereof, and relates to the field of resistance measuring technology, and is characterized in that it comprises: a measuring circuit module, a microcontroller, a display module and a key module; the measuring circuit module comprises a resistance to be measured, an adjusting resistor, a voltage amplifier shunt resistor, a voltage amplifier voltage dividing resistor, a voltage amplifier equivalent resistor, a voltage amplifier, a first relay, a second relay and a power supply. The technical problem to be solved by the present invention is to provide a resistance measuring circuit and a resistance measuring method thereof, and the electrical connection relationship between the voltage amplifier and other components in the measuring circuit module is changed by the first relay and the second relay, so as to realize the conversion between the external connection method measurement and the internal connection method measurement of the resistance, and the conversion between the current measurement and the voltage measurement, so as to realize the volt-ampere method measurement of the resistance with only one voltage amplifier, and the measurement accuracy is high and the operation steps are simple.

Description

Technical Field

[0001] The present invention relates to the technical field of resistance measurement, and in particular to a resistance measurement circuit and a resistance measurement method thereof. Background Art

[0002] As the most common electronic component, the accuracy of resistors directly affects the stability and accuracy of the entire circuit system. At present, in the production process of electronic products, the first step in testing the functional quality of products is to measure the resistor.

[0003] There are many methods and equipment for measuring resistance. The main methods for measuring resistance are as follows: 1. Volt-ampere method, that is, calculating resistance by measuring current and voltage; 2. Bridge measurement method; 3. Voltage divider test method; 4. Kelvin four-wire detection (four-terminal detection) method, etc. The equipment and instruments for resistance testing are mainly divided into two categories: 1. Standard equipment and instruments, such as ohmmeter, LCR meter, etc.; 2. Functional boards, special boards designed for various occasions and needs, basically provide current sources with different gears, measure the voltage across the resistor to be measured, and then calculate the resistance value. The volt-ampere method and the four-terminal detection method have high accuracy, but two instruments (or voltage amplifiers) are required for measuring resistance, namely, a voltmeter and an ammeter, and the operation steps are relatively cumbersome; while the ohmmeter only needs one instrument (or voltage amplifier) ​​to measure resistance, and the operation steps are simple, but the measurement accuracy is low. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a resistance measuring circuit and a resistance measuring method thereof, wherein the electrical connection relationship between a voltage amplifier and other components in a measuring circuit module is changed by a first relay and a second relay, so as to realize the conversion between external connection method measurement and internal connection method measurement of resistance, and the conversion between current measurement and voltage measurement, thereby realizing the volt-ampere method measurement of resistance with only one voltage amplifier, and the measurement accuracy is high and the operation steps are simple.

[0005] The present invention adopts the following technical solutions to achieve the invention objectives:

[0006] A resistance measurement circuit, characterized in that it comprises: a measurement circuit module, a microcontroller, a display module and a key module; the measurement circuit module comprises a resistance to be measured , Adjust the resistance , Voltage Amplifier Shunt Resistors , Voltage amplifier voltage divider resistor , voltage amplifier equivalent resistor , voltage amplifier 111, a first relay KA1, a second relay KA2 and a power supply; the voltage amplifier, the first relay KA1, the second relay KA2, the display module and the key module are electrically connected to the microcontroller respectively.

[0007] As a further limitation of the present technical solution, the adjusting resistor One end is electrically connected to the voltage amplifier voltage divider resistor One end of the resistor to be measured One end of the voltage amplifier divider resistor The other end is electrically connected to the pins NO2 and NC3 of the second relay KA2, and the resistance to be measured The other end is electrically connected to the pins NO1, NC2, NC3 and NO3 of the first relay KA1 and the voltage amplifier shunt resistor The power supply is electrically connected to the voltage amplifier shunt resistor The other end of the first relay KA1, the pins NC1 and NO2 of the first relay KA1 and the pin NO1 of the second relay KA2, the pin COM1 of the first relay KA1 is electrically connected to the pin NC1 of the second relay KA2 and the voltage amplifier equivalent resistor The pin COM2 of the first relay KA1 is electrically connected to the pin NC2 of the second relay KA2, the pin COM3 of the first relay KA1 is electrically connected to the pin NO3 of the second relay KA2, the pin COM1 of the second relay KA2 is electrically connected to the positive input terminal of the voltage amplifier, and the pin COM2 of the second relay KA2 is electrically connected to the equal value resistor of the voltage amplifier. At the other end, the pin COM3 of the second relay KA2 is electrically connected to the negative input terminal of the voltage amplifier.

[0008] As a further limitation of the present technical solution, the first relay KA1 and the second relay KA2 are used to change the electrical connection relationship between the voltage amplifier and other components in the measurement circuit module, so as to realize the conversion between external connection method and internal connection method of resistance measurement, and the conversion between current measurement and voltage measurement.

[0009] As a further limitation of the present technical solution, the power supply adopts a linear DC regulated power supply for supplying a voltage to the resistance to be measured. , voltage amplifier, microcontroller and first relay KA1 and second relay KA2 are powered.

[0010] As a further limitation of the present technical solution, the voltage amplifier is used to measure the resistance to be measured. or voltage amplifier shunt resistor The voltage on the voltage is amplified and transmitted to the AD acquisition unit of the microcontroller. When the voltage amplifier and the voltage amplifier shunt resistor In parallel, a current measurement unit can be formed, by measuring the voltage amplifier shunt resistor The voltage of the current measuring unit can be used to calculate the resistance to be measured in series with the current measuring unit. When the voltage amplifier and the voltage amplifier voltage divider resistor connected in series to form a voltage measurement unit, by measuring the resistance to be measured The voltage of the resistor to be measured connected in parallel with the voltage measuring unit can be calculated voltage.

[0011] A resistance measuring method of a resistance measuring circuit comprises the following steps:

[0012] S1: Turn on the machine;

[0013] S2: Pressing the reset button of the key module, the control unit of the microcontroller is initialized, and the resistance value information displayed by the display module is cleared;

[0014] S3: Press the automatic measurement key of the key module to perform external measurement:

[0015] S31: The control unit sends a low level signal to the first relay KA1 and sends a low level signal to the second relay KA2 to The current is measured by external connection method;

[0016] S32: The control unit sends a low level signal to the first relay KA1, but does not send a low level signal to the second relay KA2, to the resistance to be measured The voltage at both ends is measured by external connection method;

[0017] S33: the calculation unit of the microcontroller calculates the resistance value measured by the external connection method according to the two measurement values;

[0018] S34: The resistance value measured by the external connection method is compared with the voltage amplifier voltage divider resistance , the voltage amplifier shunt resistor If the external connection conditions are met, , then maintain the external connection method and send the resistance value information to the display module; if the internal connection method condition is met , the internal connection method is automatically selected to re-measure;

[0019] S4: Perform internal connection measurement:

[0020] S41: The control unit does not send a low level signal to the first relay KA1, but sends a low level signal to the second relay KA2, so that the current flowing through the resistor to be measured The current is measured by internal connection method;

[0021] S42: The control unit does not send a low level signal to the first relay KA1, and does not send a low level signal to the second relay KA2, so that the resistance to be measured The voltage at both ends is measured by internal connection method;

[0022] S43: The calculation unit calculates the resistance value measured by the internal connection method according to the two measurement values;

[0023] S5: After the calculation is completed, the control unit of the microcontroller sends the resistance value information to the display module to display the result.

[0024] Compared with the prior art, the advantages and positive effects of the present invention are:

[0025] The present invention provides a resistance measuring circuit and a resistance measuring method thereof. The electrical connection relationship between a voltage amplifier and other components in a measuring circuit module is changed by a first relay and a second relay, so as to realize the conversion between external connection method measurement and internal connection method measurement of resistance, and the conversion between current measurement and voltage measurement. Thus, the volt-ampere method measurement of resistance is realized with only one voltage amplifier, and the measurement accuracy is high and the operation steps are simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the present invention.

[0027] Figure 2 It is a circuit diagram of the present invention.

[0028] Figure 3 It is an equivalent circuit diagram of the measuring circuit module of the present invention when KA1 is in a normally closed state and KA2 is in a normally open state.

[0029] Figure 4 It is an equivalent circuit diagram of the measuring circuit module of the present invention when KA1 is in a normally closed state and KA2 is in a normally closed state.

[0030] Figure 5 It is an equivalent circuit diagram of the measuring circuit module of the present invention when KA1 is in a normally open state and KA2 is in a normally open state.

[0031] Figure 6 It is an equivalent circuit diagram of the measuring circuit module of the present invention when KA1 is in a normally open state and KA2 is in a normally closed state.

[0032] Figure 7 It is a schematic diagram of the resistance measurement method of the present invention.

[0033] In the figure: 110, measurement circuit module; 111, voltage amplifier; 120, microcontroller; 130, display module; 140, key module. DETAILED DESCRIPTION

[0034] A specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation.

[0035] The present invention comprises: a measuring circuit module 110, a microcontroller 120, a display module 130 and a key module 140;

[0036] The measuring circuit module 110 includes a resistor to be measured , Adjust the resistance , Voltage Amplifier Shunt Resistors , Voltage amplifier voltage divider resistor , voltage amplifier equivalent resistor , voltage amplifier 111, a first relay KA1, a second relay KA2 and a power supply; the voltage amplifier 111, the first relay KA1, the second relay KA2, the display module 130 and the key module 140 are electrically connected to the microcontroller 120 respectively.

[0037] The adjusting resistor One end is electrically connected to the voltage amplifier voltage divider resistor One end of the resistor to be measured One end of the adjusting resistor The other end is grounded, and the voltage amplifier divider resistor The other end is electrically connected to the pins NO2 and NC3 of the second relay KA2, and the resistance to be measured The other end is electrically connected to the pins NO1, NC2, NC3 and NO3 of the first relay KA1 and the voltage amplifier shunt resistor The power supply is electrically connected to the voltage amplifier shunt resistor The other end of the first relay KA1, the pins NC1 and NO2 of the first relay KA1 and the pin NO1 of the second relay KA2, the pin COM1 of the first relay KA1 is electrically connected to the pin NC1 of the second relay KA2 and the voltage amplifier equivalent resistor The pin COM2 of the first relay KA1 is electrically connected to the pin NC2 of the second relay KA2, the pin COM3 of the first relay KA1 is electrically connected to the pin NO3 of the second relay KA2, the pin COM1 of the second relay KA2 is electrically connected to the positive input terminal of the voltage amplifier 111, and the pin COM2 of the second relay KA2 is electrically connected to the equal value resistor of the voltage amplifier The other end of the second relay KA2 is electrically connected to the negative input terminal of the voltage amplifier 111, and the pin COM3 of the second relay KA2 is electrically connected to the negative input terminal of the voltage amplifier 111.

[0038] The output end of the voltage amplifier 111 is electrically connected to the microcontroller 120, the GND of the first relay KA1 is electrically connected to the negative pole of the power supply, VCC is electrically connected to the positive pole of the power supply, and each signal input end is electrically connected to the microcontroller 120, the GND of the second relay KA2 is electrically connected to the negative pole of the power supply, VCC is electrically connected to the positive pole of the power supply, and each signal input end is electrically connected to the microcontroller 120.

[0039] The adjusting resistor Refers to the resistance to be measured A series resistor is used to control the current flowing through the resistor to be measured. of current.

[0040] The voltage amplifier shunt resistor Refers to a resistor connected in parallel with the voltage amplifier 111, used to be connected in parallel with the voltage amplifier 111, the voltage amplifier shunt resistor With the voltage amplifier 111 (assuming the range is ) can be connected in parallel to form a measuring range of The current measuring unit. Since the voltage amplifier shunt resistor In parallel with the voltage amplifier 111, the voltage amplifier shunt resistor The voltage across Equal to the range of the voltage amplifier 111 ,Right now:

[0041] (1);

[0042] Where: Voltage amplifier shunt resistance for full-scale measurement The voltage across the terminals;

[0043] is the range of the voltage amplifier 111;

[0044] The current range of the current measuring unit Equal to the current range of the voltage amplifier 111 The voltage amplifier is connected in parallel with a shunt resistor Current The sum is:

[0045] (2);

[0046] Where: is the current range of the current measuring unit;

[0047] is the resistance value of the voltage amplifier 111.

[0048] The required parallel voltage amplifier shunt resistor is obtained from formulas (1) and (2): Resistance value:

[0049] (3);

[0050] The voltage amplifier divider resistor Refers to a resistor connected in series with the voltage amplifier 111, used to be connected in series with the voltage amplifier 111, the voltage amplifier voltage divider resistor With the voltage amplifier 111 (assuming the range is ) can be connected in series to form a measuring range of The voltage amplifier divides the resistor is connected in series with the voltage amplifier 111, and flows through the voltage amplifier voltage divider resistor Current Equal to the current range flowing through the voltage amplifier 111 ,Right now:

[0051] (4);

[0052] Where: When measuring full scale, the voltage amplifier divider resistor The current;

[0053] is the current range flowing through the voltage amplifier 111.

[0054] The magnitude of the current flowing through the voltage amplifier 111 is:

[0055] (5);

[0056] The voltage range across the voltage measuring unit is equal to the voltage range on the voltage amplifier 111 ( ) with the voltage amplifier divider resistor in series The partial pressure on ), that is:

[0057] (6);

[0058] Where: is the voltage range of the voltage measurement unit.

[0059] The voltage amplifier voltage divider resistors required to be connected in series are obtained from formulas (4), (5), and (6): Resistance value:

[0060] (7);

[0061] The voltage amplifier has an equivalent resistor It means that its resistance value is equal to the resistance value of the voltage amplifier 111 The resistance ( ), when the voltage amplifier 111 and the voltage amplifier shunt resistor When connected in parallel to form a current measurement unit, the voltage amplifier has an equivalent resistor Replace the voltage amplifier 111 and the voltage amplifier voltage divider resistor When the voltage amplifier 111 and the voltage amplifier voltage dividing resistor are connected in series; When the voltage measurement unit is formed in series, the voltage amplifier has the same value of resistance Replace the voltage amplifier 111 with the voltage amplifier shunt resistor in parallel.

[0062] The voltage amplifier has an equivalent resistor is a precision resistor having a resistance value equal to that of the voltage amplifier 111 .

[0063] The first relay KA1 and the second relay KA2 are used to change the electrical connection relationship between the voltage amplifier 111 and other components in the measurement circuit module 110, so as to realize the conversion between the external connection method and the internal connection method of the resistance measurement, and the conversion between the current measurement and the voltage measurement.

[0064] The first relay KA1 and the second relay KA2 are both Risym brand 4-way relay modules, which have optocoupler isolation, support high and low level triggering, and are powered by 5V voltage. The 4-way relay module in the present invention adopts a low-level trigger connection. When the signal input end of the relay does not receive a low-level signal from the microcontroller 120, the relay is in a normally closed state, that is, the COM end (common end) and the NC end (normally closed end) of the relay are attracted together; when the signal input end of the relay receives a low-level signal from the microcontroller 120, the relay is in a normally open state, that is, the COM end and the NO end (normally open end) are attracted.

[0065] refer to Figure 2, when the microcontroller 120 does not send a low-level signal to the first relay KA1, but sends a low-level signal to the second relay KA2, the first relay KA1 is in a normally closed state, and the second relay KA2 is in a normally open state. That is, the common terminal contact COM1 of KA1 is electrically connected to the normally closed terminal contact NC1; the common terminal contact COM2 is electrically connected to the normally closed terminal contact NC2; the common terminal contact COM3 is electrically connected to the normally closed terminal contact NC3; the common terminal contact COM4 is electrically connected to the normally closed terminal contact NC4; the common terminal contact COM1 of KA2 is electrically connected to the normally open terminal contact NO1; the common terminal contact COM2 is electrically connected to the normally open terminal contact NO2; the common terminal contact COM3 is electrically connected to the normally open terminal contact NO3; the common terminal contact COM4 is electrically connected to the normally open terminal contact NO4; its equivalent circuit diagram is as follows Figure 3 As shown, the voltage amplifier 111 and the voltage amplifier shunt resistor The current measuring unit is connected in parallel and can be regarded as an "ammeter" in function, which is used to measure the current flowing through the resistor to be measured. The current is measured; due to , from the perspective of the impact on current and voltage, the voltage amplifier equivalent resistance Voltage divider resistors with voltage amplifier The circuit formed in series is equivalent to the voltage amplifier 111 and the voltage amplifier voltage dividing resistor The voltage measurement unit circuit is composed of series connection, and the voltage measurement unit can be regarded as a "voltmeter", so Figure 3 The circuit connection relationship shown can be regarded as the "ammeter" internal connection method (abbreviated as internal connection method), which is used to measure the current flowing through the resistor to be measured. The current is measured by the internal connection method.

[0066] refer to Figure 2 , when the microcontroller 120 does not send a low-level signal to the first relay KA1, nor does it send a low-level signal to the second relay KA2, the first relay KA1 is in a normally closed state, and the second relay KA2 is also in a normally closed state. That is, the common terminal contact COM1 of KA1 is electrically connected to the normally closed terminal contact NC1; the common terminal contact COM2 is electrically connected to the normally closed terminal contact NC2; the common terminal contact COM3 is electrically connected to the normally closed terminal contact NC3; the common terminal contact COM4 is electrically connected to the normally closed terminal contact NC4; the common terminal contact COM1 of KA2 is electrically connected to the normally closed terminal contact NC1; the common terminal contact COM2 is electrically connected to the normally closed terminal contact NC2; the common terminal contact COM3 is electrically connected to the normally closed terminal contact NC3; the common terminal contact COM4 is electrically connected to the normally closed terminal contact NC4; its equivalent circuit diagram is as follows Figure 4 As shown, the voltage amplifier 111 and the voltage amplifier voltage divider resistor The voltage measurement unit is connected in series and can be regarded as a "voltmeter" in function. The voltage across the two ends is measured; , from the perspective of the impact on current and voltage, the voltage amplifier equivalent resistance Shunt resistor with voltage amplifier The circuit formed in parallel is equivalent to the voltage amplifier 111 and the voltage amplifier shunt resistor The current measuring unit circuit is composed of two parallel connections, and the current measuring unit can be regarded as an "ammeter", so Figure 4 The circuit connection relationship shown can be regarded as the internal connection method of "ammeter" and is used for the resistance to be measured. The voltage across the terminals is measured using the internal connection method.

[0067] because , from the perspective of the impact on current and voltage, Figure 3 The circuit shown is equivalent to Figure 4 The circuit shown, Figure 3 , Figure 4 Resistance to be measured The voltage at both ends remains unchanged and can be set to , flows through the resistor to be measured The current remains unchanged and can be set to .

[0068] refer to Figure 3 , flows through the resistor to be measured Current is equal to the current flowing through the voltage amplifier 111 and flows through the voltage amplifier shunt resistor Current The sum of

[0069] (8);

[0070] Where: When measuring current by internal connection method, it flows through the resistance to be measured. The current;

[0071] is the current flowing through the voltage amplifier 111 when measuring current using the internal connection method;

[0072] When measuring current by internal connection method, the current flows through the voltage amplifier shunt resistor of current.

[0073] refer to Figure 3 , the voltage at the positive and negative input terminals of the voltage amplifier 111 is equal to the voltage amplifier shunt resistance The voltage across , so the current flowing through the voltage amplifier 111 when measuring current using the internal connection method is:

[0074] (9);

[0075] Where: The voltage amplifier shunt resistor when measuring current by internal connection method The voltage across both ends.

[0076] When measuring current by internal connection method, the current flows through the voltage amplifier shunt resistor Current:

[0077] (10);

[0078] The output voltage of the voltage amplifier 111 Equal to the voltage at the positive and negative input terminals of the voltage amplifier 111 The amplification gain value of the voltage amplifier 111 The product of, that is:

[0079] (11);

[0080] Where: is the output voltage of the voltage amplifier 111 when measuring current using the internal connection method, is the amplification gain value of the voltage amplifier 111.

[0081] According to formulas (8), (9), (10), and (11), the current flowing through the resistor to be measured is Current:

[0082] (12);

[0083] refer to Figure 4 , resistance to be measured The voltage across Shunt resistor with voltage amplifier The voltage across The sum is equal to the voltage at the positive and negative input terminals of the voltage amplifier 111 Voltage divider resistors with voltage amplifier The voltage across The sum is:

[0084] (13);

[0085] Where: The resistance to be measured when measuring voltage by internal connection method The voltage across the terminals;

[0086] When measuring voltage by internal connection method, the voltage amplifier shunt resistor The voltage across the terminals;

[0087] The voltages at the positive and negative input terminals of the voltage amplifier 111 when measuring voltage using the internal connection method;

[0088] Voltage amplifier voltage divider resistor when measuring voltage using the internal connection method The voltage across both ends.

[0089] The voltages at the positive and negative input terminals of the voltage amplifier 111 are:

[0090] (14);

[0091] Voltage Amplifier Divider Resistors The voltage across the terminals:

[0092] (15);

[0093] refer to Figure 4 , flows through the voltage amplifier divider resistor Current is equal to the current flowing through the voltage amplifier 111 ,Right now:

[0094] (16);

[0095] The output voltage of the voltage amplifier 111 Equal to the voltage at the positive and negative input terminals of the voltage amplifier 111 The amplification gain value of the voltage amplifier 111 The product of

[0096] (17);

[0097] Where: The output voltage of the voltage amplifier 111 when measuring voltage by the internal connection method;

[0098] is the amplification gain value of the voltage amplifier 111;

[0099] It is the voltage at the positive and negative input terminals of the voltage amplifier 111 when measuring voltage using the internal connection method.

[0100] From formulas (9), (13), (14), (15), (16), and (17), we get

[0101] (18);

[0102] consider and The parallel resistance value , , , formula (18) divided by formula (12) yields:

[0103] (19);

[0104] because , formula (19) can be written as:

[0105] (20);

[0106] when When the resistance to be measured Approximate resistance value:

[0107] (twenty one);

[0108] Since the resistance value of the voltage amplifier 111 , Voltage Amplifier Shunt Resistors , Voltage amplifier voltage divider resistor are all constants, so the resistance to be measured Proportional to the voltage ratio ( U 2 / U 1 ).

[0109] refer to Figure 2 , when the microcontroller 120 sends a low level signal to the first relay KA1 and also sends a low level signal to the second relay KA2, the first relay KA1 is in a normally open state, and the second relay KA2 is also in a normally open state. That is, the common terminal contact COM1 of KA1 is electrically connected to the normally open terminal contact NO1; the common terminal contact COM2 is electrically connected to the normally open terminal contact NO2; the common terminal contact COM3 is electrically connected to the normally open terminal contact NO3; the common terminal contact COM4 is electrically connected to the normally open terminal contact NO4; the common terminal contact COM1 of KA2 is electrically connected to the normally open terminal contact NO1; the common terminal contact COM2 is electrically connected to the normally open terminal contact NO2; the common terminal contact COM3 is electrically connected to the normally open terminal contact NO3; the common terminal contact COM4 is electrically connected to the normally open terminal contact NO4; its equivalent circuit diagram is as follows Figure 5 As shown, the voltage amplifier 111 and the voltage amplifier shunt resistor The current measuring unit is connected in parallel and can be regarded as an "ammeter" in function, which is used to measure the current flowing through the resistor to be measured. The current is measured; due to , from the perspective of the impact on current and voltage, the voltage amplifier equivalent resistance Voltage divider resistors with voltage amplifier The circuit formed in series is equivalent to the voltage amplifier 111 and the voltage amplifier voltage dividing resistor The voltage measurement unit circuit is composed of series connection, and the voltage measurement unit can be regarded as a "voltmeter", so Figure 5The circuit connection relationship shown can be regarded as the "current meter" external connection method (external connection method for short), which is used to measure the current flowing through the resistor to be measured. The current is measured by external connection method.

[0110] refer to Figure 2 , when the microcontroller 120 sends a low-level signal to the first relay KA1, but does not send a low-level signal to the second relay KA2, the first relay KA1 is in a normally open state, and the second relay KA2 is in a normally closed state. That is, the common terminal contact COM1 of KA1 is electrically connected to the normally open terminal contact NO1; the common terminal contact COM2 is electrically connected to the normally open terminal contact NO2; the common terminal contact COM3 is electrically connected to the normally open terminal contact NO3; the common terminal contact COM4 is electrically connected to the normally open terminal contact NO4; the common terminal contact COM1 of KA2 is electrically connected to the normally closed terminal contact NC1; the common terminal contact COM2 is electrically connected to the normally closed terminal contact NC2; the common terminal contact COM3 is electrically connected to the normally closed terminal contact NC3; the common terminal contact COM4 is electrically connected to the normally closed terminal contact NC4; its equivalent circuit diagram is as follows Figure 6 As shown, the voltage amplifier 111 and the voltage amplifier voltage divider resistor The voltage measurement unit is connected in series and can be regarded as a "voltmeter" in function. The voltage across the two ends is measured; , from the perspective of the impact on current and voltage, the voltage amplifier equivalent resistance Shunt resistor with voltage amplifier The circuit formed in parallel is equivalent to the voltage amplifier 111 and the voltage amplifier shunt resistor The current measuring unit circuit is composed of two parallel connections, and the current measuring unit can be regarded as an "ammeter", so Figure 6 The circuit connection relationship shown can be regarded as the "current meter" external connection method, which is used to measure the resistance The voltage across the two ends is measured using the external connection method.

[0111] because , from the perspective of the impact on current and voltage, Figure 5 The circuit shown is equivalent to Figure 6 The circuit shown, Figure 5 , Figure 6 Resistance to be measured The voltage at both ends remains unchanged and can be set to , flows through the resistor to be measured The current remains unchanged and can be set to .

[0112] refer to Figure 5 , flows through the resistor to be measured Current and flows through the voltage amplifier divider resistor Current The sum is equal to the current flowing through the voltage amplifier shunt resistor Current The current flowing through the voltage amplifier 111 The sum of

[0113] (twenty two);

[0114] Where: When measuring current by external connection method, it flows through the resistance to be measured. The current;

[0115] When measuring current by external connection method, the voltage amplifier divider resistor flows through the voltage amplifier The current;

[0116] When measuring current by external connection method, the current flows through the voltage amplifier shunt resistor The current;

[0117] It is the current flowing through the voltage amplifier 111 when measuring current by the external connection method.

[0118] refer to Figure 5 , the voltage at the positive and negative input terminals of the voltage amplifier 111 (the current flowing through the voltage amplifier 111 The resistance value of the voltage amplifier 111 The product of the voltage amplifier shunt resistance The voltage across ,Right now:

[0119] (twenty three);

[0120] Where: The voltage amplifier shunt resistor when measuring current by external connection method The voltage across both ends.

[0121] Flow through the voltage amplifier shunt resistor Current Shunt resistor with voltage amplifier The product is equal to the voltage amplifier shunt resistance The voltage across ,Right now:

[0122] (twenty four);

[0123] The output voltage of the voltage amplifier Equal to the voltage at the positive and negative input terminals of the voltage amplifier 111 The amplification gain value of the voltage amplifier 111 The product of, that is:

[0124] (25);

[0125] Where: The output voltage of the voltage amplifier 111 when measuring current by the external connection method;

[0126] is the amplification gain value of the voltage amplifier 111;

[0127] It is the voltage at the positive and negative input terminals of the voltage amplifier 111 when measuring current using the external connection method.

[0128] From formulas (22), (23), (24), and (25), we get:

[0129] (26);

[0130] refer to Figure 6 , resistance to be measured The voltage across Equal to the voltage at the positive and negative input terminals of the voltage amplifier 111 Voltage divider resistors with voltage amplifier The voltage across The sum is:

[0131] (27);

[0132] Where: The resistance to be measured when measuring voltage by external connection method The voltage across the terminals;

[0133] The voltages at the positive and negative input terminals of the voltage amplifier 111 when measuring voltage using the external connection method;

[0134] Voltage amplifier voltage divider resistor when measuring voltage using external method The voltage across both ends.

[0135] The voltages at the positive and negative input terminals of the voltage amplifier 111 are:

[0136] (28);

[0137] Voltage Amplifier Divider Resistors The voltage across the terminals:

[0138] (29);

[0139] refer to Figure 6 , the current flowing through the voltage amplifier 111 Equal to the voltage amplifier divider resistor Current ,Right now:

[0140] (30);

[0141] The output voltage of the voltage amplifier Equal to the voltage at the positive and negative input terminals of the voltage amplifier 111 The amplification gain value of the voltage amplifier 111 The product of, that is:

[0142] (31);

[0143] Where: The output voltage of the voltage amplifier 111 when measuring voltage by the external connection method;

[0144] is the amplification gain value of the voltage amplifier 111;

[0145] It is the voltage at the positive and negative input terminals of the voltage amplifier 111 when measuring voltage by the external connection method.

[0146] From formulas (23), (27), (28), (29), (30), and (31), we get:

[0147] (32);

[0148] refer to Figure 5 , Figure 6 ,consider and The series resistance value , and The parallel resistance value , , formula (32) divided by formula (26) yields:

[0149] (33);

[0150] then , , resistance to be measured Approximate resistance value:

[0151] (34);

[0152] Since the resistance value of the voltage amplifier 111 , Voltage Amplifier Shunt Resistors , Voltage amplifier voltage divider resistor are all constants, so the resistance to be measured Proportional to the voltage ratio ( ).

[0153] The power supply adopts a 15V linear DC regulated power supply to supply power to the resistance to be measured. , voltage amplifier 111 and microcontroller 120 are powered; 15V can be reduced to 5V through the DCDC step-down circuit, which is used to power the first relay KA1 and the second relay KA2.

[0154] The voltage amplifier 111 (symbol VA) is used to measure the resistance to be measured. or voltage amplifier shunt resistor The voltage on the voltage amplifier 111 is amplified and then transmitted to the AD acquisition unit of the microcontroller 120. In parallel, a current measurement unit can be formed, by measuring the voltage amplifier shunt resistor The voltage of the current measuring unit can be used to calculate the resistance to be measured in series with the current measuring unit. When the voltage amplifier 111 and the voltage amplifier voltage divider resistor connected in series to form a voltage measurement unit, by measuring the resistance to be measured The voltage of the resistor to be measured connected in parallel with the voltage measuring unit can be calculated voltage.

[0155] The voltage amplifier 111 uses a millivolt / microvolt single-ended differential voltage amplifier, which requires a maximum nonlinearity of 40ppm, a low offset voltage not exceeding 50uV and a low offset drift of a maximum of 0.6uV / °C, an input range of 50uV to 4V, an output that does not exceed the limit acquisition voltage of 3.6V of the AD acquisition module of the microcontroller, and an amplification factor of not less than 250 times.

[0156] The microcontroller 120 is provided with an AD acquisition unit, a calculation unit and a control unit. The AD of the microcontroller is used to collect the output voltage of the voltage amplifier and send the amplified voltage to the calculation unit of the microcontroller. The calculation unit of the microcontroller calculates the resistance to be measured according to the voltages measured twice before and after. and sends the resistance value to the LCD display module 130. The control unit of the microcontroller is used to control the normally open state and the normally closed state of the first relay KA1 and the second relay KA2.

[0157] The microcontroller 120 adopts STM32F103, the STM32F103 core adopts ARM 32-bit Cortex-M3, the memory adopts SRAM with a maximum of 64K bytes, the analog-to-digital converter adopts two 12-bit analog-to-digital converters, and the calculation unit adopts a CRC calculation unit.

[0158] The display module 130 uses a high-resolution 800*480 LCD display screen, has its own driver, does not require an external driver, supports 8 / 9 / 12 / 16-bit 8080 parallel port connection, and has a backlight brightness control function.

[0159] The key module 140 includes a reset key and an automatic measurement key. The reset key and the automatic measurement key are connected to the control unit of the microcontroller respectively. When the reset key is pressed, the control unit of the microcontroller is initialized and the resistance value information displayed on the LCD is cleared; when the automatic measurement key is pressed, the current measurement and voltage measurement of the external connection method are automatically performed, and the resistance value is calculated according to the current and voltage measurement values, and then the voltage amplifier divider resistor is used to calculate the resistance value. , Voltage Amplifier Shunt Resistors , voltage amplifier equivalent resistor Compare and if the external connection condition is met: , then the external connection method is maintained; if the internal connection method conditions are met: , select the internal connection method to re-measure the current and voltage of the internal connection method, and recalculate the resistance value based on the current and voltage measurement values.

[0160] A resistance measurement method for a resistance measurement circuit, referring to Figure 7 , including the following steps:

[0161] S1: Turn on the machine;

[0162] S2: Pressing the reset button of the button module 140, the control unit of the microcontroller 120 is initialized, and the resistance value information displayed by the display module 130 is cleared;

[0163] S3: Press the automatic measurement key of the key module 140 to perform external measurement:

[0164] S31: The control unit sends a low level signal to the first relay KA1 and sends a low level signal to the second relay KA2 to The current is measured by external connection method;

[0165] S32: The control unit sends a low level signal to the first relay KA1, but does not send a low level signal to the second relay KA2, to the resistance to be measured The voltage at both ends is measured by external connection method;

[0166] S33: the calculation unit of the microcontroller 120 calculates the resistance value measured by the external connection method according to the two measurement values ​​according to formula (34);

[0167] S34: The resistance value measured by the external connection method is compared with the voltage amplifier voltage divider resistance , the voltage amplifier shunt resistor If the external connection conditions are met, the resistance value is compared: , the external connection method is maintained, and the resistance value information is sent to the display module 130 to display the result; if the internal connection method conditions are met: , the internal connection method is automatically selected to re-measure;

[0168] S4: Perform internal connection measurement:

[0169] S41: The control unit does not send a low level signal to the first relay KA1, but sends a low level signal to the second relay KA2, so that the current flowing through the resistor to be measured The current is measured by internal connection method;

[0170] S42: The control unit does not send a low level signal to the first relay KA1, and does not send a low level signal to the second relay KA2, so that the resistance to be measured The voltage at both ends is measured by internal connection method;

[0171] S43: the calculation unit calculates the resistance value measured by the internal connection method according to the two measurement values ​​according to formula (21);

[0172] S5: After the calculation is completed, the control unit of the microcontroller sends the resistance value information to the display module 130 to display the result.

[0173] The present invention provides a resistance measuring circuit and a resistance measuring method thereof. The electrical connection relationship between a voltage amplifier 111 and other components in a measuring circuit module 110 is changed by a first relay KA1 and a second relay KA2, so as to realize the conversion between external connection method measurement and internal connection method measurement of resistance, and the conversion between current measurement and voltage measurement. Thus, the volt-ampere method measurement of resistance is realized with only one voltage amplifier, and the measurement accuracy is high and the operation steps are simple.

[0174] The above disclosure is only a specific embodiment of the present invention, but the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A resistance measuring circuit, characterized in that: include: A measuring circuit module (110), a microcontroller (120), a display module (130) and a key module (140); The measuring circuit module (110) comprises a resistor to be measured , Adjust the resistance , Voltage Amplifier Shunt Resistors , Voltage amplifier voltage divider resistor , voltage amplifier equivalent resistor , a voltage amplifier (111), a first relay KA1, a second relay KA2 and a power supply; The voltage amplifier (111), the first relay KA1, the second relay KA2, the display module (130) and the key module (140) are respectively electrically connected to the microcontroller (120); The adjusting resistor One end is electrically connected to the voltage amplifier voltage divider resistor One end of the resistor to be measured One end of the voltage amplifier divider resistor The other end is electrically connected to the pins NO2 and NC3 of the second relay KA2, and the resistance to be measured The other end is electrically connected to the pins NO1, NC2, NC3 and NO3 of the first relay KA1 and the voltage amplifier shunt resistor The power supply is electrically connected to the voltage amplifier shunt resistor The other end of the first relay KA1, the pins NC1 and NO2 of the first relay KA1 and the pin NO1 of the second relay KA2, the pin COM1 of the first relay KA1 is electrically connected to the pin NC1 of the second relay KA2 and the voltage amplifier equivalent resistor The pin COM2 of the first relay KA1 is electrically connected to the pin NC2 of the second relay KA2, the pin COM3 of the first relay KA1 is electrically connected to the pin NO3 of the second relay KA2, the pin COM1 of the second relay KA2 is electrically connected to the positive input terminal of the voltage amplifier (111), and the pin COM2 of the second relay KA2 is electrically connected to the equal value resistor of the voltage amplifier. The other end of the second relay KA2, the pin COM3 of the second relay KA2 is electrically connected to the negative input terminal of the voltage amplifier (111).

2. The resistance measuring circuit according to claim 1, characterized in that: The first relay KA1 and the second relay KA2 are used to change the electrical connection relationship between the voltage amplifier (111) and other components in the measurement circuit module (110), thereby realizing the conversion between external connection method measurement and internal connection method measurement of resistance, and the conversion between current measurement and voltage measurement.

3. The resistance measuring circuit according to claim 2, characterized in that: The voltage amplifier (111) is used to measure the resistance to be measured. or voltage amplifier shunt resistor The voltage on the microcontroller (120) is amplified and then transmitted to the AD acquisition unit of the microcontroller (120). When the voltage amplifier (111) and the voltage amplifier shunt resistor parallel, forming a current measurement unit, by measuring the voltage amplifier shunt resistor The voltage is calculated to calculate the resistance to be measured in series with the current measuring unit When the voltage amplifier (111) and the voltage amplifier voltage divider resistor series, forming a voltage measurement unit, by measuring the resistance to be measured The voltage of the voltage measuring unit is calculated to determine the resistance to be measured in parallel with the voltage measuring unit. voltage.

4. The resistance measuring circuit according to claim 1, characterized in that: The power supply adopts a linear DC regulated power supply to supply the resistance to be measured. , the voltage amplifier (111), the microcontroller (120), the first relay KA1, and the second relay KA2 are powered.

5. A resistance measuring method using the resistance measuring circuit according to claim 4, characterized in that: The following steps are involved: S1: Turn on the machine; S2: pressing the reset button of the key module (140), initializing the control unit of the microcontroller (120), and clearing the resistance value information displayed by the display module (130); S3: Press the automatic measurement key of the key module (140) to perform external measurement: S31: The control unit sends a low level signal to the first relay KA1 and sends a low level signal to the second relay KA2 to The current is measured by external connection method; S32: The control unit sends a low level signal to the first relay KA1, but does not send a low level signal to the second relay KA2, to the resistance to be measured The voltage at both ends is measured by external connection method; S33: the calculation unit of the microcontroller (120) calculates the resistance value measured by the external connection method according to the two measurement values; S34: The resistance value measured by the external connection method is compared with the voltage amplifier voltage divider resistance , the voltage amplifier shunt resistor The resistance value is compared to meet the external connection conditions: , the external connection method is maintained, and the resistance value information is sent to the display module (130); the internal connection method condition is met: , the internal connection method is automatically selected to re-measure; S4: Perform internal connection measurement: S41: The control unit does not send a low level signal to the first relay KA1, but sends a low level signal to the second relay KA2, so that the current flowing through the resistor to be measured The current is measured by internal connection method; S42: The control unit does not send a low level signal to the first relay KA1, and does not send a low level signal to the second relay KA2, so that the resistance to be measured The voltage at both ends is measured by internal connection method; S43: The calculation unit calculates the resistance value measured by the internal connection method according to the two measurement values; S5: After the calculation is completed, the control unit of the microcontroller sends the resistance value information to the display module (130) to display the result.

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