Current reference source circuit for direct current resistance tester

Abstract

The utility model discloses a current reference source circuit for a direct current resistance tester, which relates to the field of precise direct current resistance testing and comprises a single chip microcomputer, a chip, an analog switch switching module, a precise resistance module and a constant voltage output module. The output end of the single-chip microcomputer is connected with the input end of the chip, the output end of the chip is connected with the input end of the analog switch switching module, the output end of the analog switch switching module is connected with the input end of the precision resistance module, and the output end of the precision resistance module is connected with the input end of the constant voltage output module. According to the current reference source circuit for the direct-current resistance tester, provided by the utility model, adjustable voltage can be output through the chip, and the precision resistance module is matched, so that the voltage output by the circuit has relatively high precision and stability.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of precision direct current resistance test, concretely relates to a current reference source circuit for direct current resistance tester. BACKGROUND

[0002] In the field of precision direct current resistance test, there are two commonly used current reference source circuits, one is a linear constant current source circuit composed of integrated operational amplifier and triode and other elements, which maintains the stability of output current through closed loop feedback system, and the other is a constant current source circuit based on voltage stabilizing chip, which contains operational amplifier and adjusting tube and other elements inside, and maintains the stability of output voltage through negative feedback mechanism.

[0003] The linear constant current source circuit composed of integrated operational amplifier and triode and other elements has higher performance requirements for components, and needs to select high-precision components to ensure the performance of the circuit, and the circuit structure is relatively complex, and the design difficulty is big, and the range of output current of the constant current source circuit based on voltage stabilizing chip is limited by the rated current of the voltage stabilizing chip itself.

[0004] Meanwhile, in the precision direct current resistance measurement, because the resistance measurement range is wide, and the measurable resistance value is very small, the sensitivity and accuracy of the measuring equipment are extremely high, so the current source of the test equipment must be very stable during the test process to ensure that the resistance value measurement is not affected by the current fluctuation, and then how to make the constant current source output constant and accurate current to improve the resistance test accuracy is the problem to be solved at present.

[0005] For the problems in the related art, no effective solution has been proposed so far. UTILITY MODEL CONTENT

[0006] In view of the problems in the related art, the utility model provides a current reference source circuit for direct current resistance tester to overcome the above technical problems existing in the prior art.

[0007] Therefore, the utility model adopts the specific technical scheme as follows:

[0008] The application discloses a current reference source circuit for a direct current resistance tester, which comprises a single-chip microcomputer for controlling output constant voltage, a chip for output adjustable voltage, an analog switch switching module for converting the chip output voltage into constant direct current voltage according to the output signal, a precision resistance module for realizing voltage amplitude adjustable function by adjusting resistance value, and a constant voltage output module for outputting constant voltage according to the adjustment result of the precision resistance module; the output end of the single-chip microcomputer is connected with the input end of the chip, the output end of the chip is connected with the input end of the analog switch switching module, the output end of the analog switch switching module is connected with the input end of the precision resistance module, and the output end of the precision resistance module is connected with the input end of the constant voltage output module.

[0009] Preferably, the chip comprises resistance R553, capacitor C550, diode D546, diode D547, resistance R554, capacitor C551 and operational amplifier U327; one end of the resistance R553 is connected with one end of the capacitor C550, one end of the diode D546, one end of the diode D547 and the eleventh pin of the operational amplifier U327 respectively, and the other end of the capacitor C550 and the other end of the diode D547 are grounded; the sixth pin of the operational amplifier U327 is connected with one end of the resistance R554 and one end of the capacitor C551 respectively, and the other end of the capacitor C551 is grounded.

[0010] Preferably, the analog switch switching module comprises a digital signal processing circuit and a switch control circuit, wherein the output end of the digital signal processing circuit is connected with the input end of the switch control circuit, and the switch control circuit is connected with the precision resistance module and the chip respectively.

[0011] Preferably, the digital signal processing circuit comprises diode D408, resistance R463, six-way inverter U311 and capacitor C5019; the fourth pin of the six-way inverter U311 is connected with the switch control circuit, the seventh pin, the ninth pin, the eleventh pin and the thirteenth pin of the six-way inverter U311 are grounded, the first pin of the six-way inverter U311 is connected with one end of the resistance R463 and the third pin of the diode D408 respectively, and the other end of the resistance R463 is grounded, the fourteenth pin of the six-way inverter U311 is connected with one end of the capacitor C5019, and the other end of the capacitor C5019 is grounded.

[0012] Preferably, the switch control circuit comprises analog switch U320D, analog switch U320A, resistor R314, resistor R322, capacitor C540 and capacitor C541; the eighth pin of the analog switch U320D is connected with the fourth pin of the six-way inverter U31, the sixth pin of the analog switch U320D is connected with the first pin of the operational amplifier U327, the seventh pin of the analog switch U320D is connected with one end of the resistor R314, and the other end of the resistor R314 is connected with one end of the precision resistor module and one end of the resistor R322 respectively; the second pin of the analog switch U320A is connected with the second pin of the operational amplifier U327, the third pin of the analog switch U320A is connected with the other end of the resistor R322, the fourth pin of the analog switch U320A is connected with one end of the capacitor C540, and the other end of the capacitor C540 is grounded, the thirteenth pin of the analog switch U320A is connected with one end of the capacitor C541, the other end of the capacitor C541 is grounded, and the fifth pin of the analog switch U320A is grounded.

[0013] Preferably, the precision resistor module comprises resistor R8, resistor R301, resistor R540, capacitor R560, operational amplifier U301A, capacitor C559 and resistor R539; one end of the resistor R8 is connected with one end of the resistor R301 and the third pin of the operational amplifier U301A respectively, and the other end of the resistor R8 is grounded, the other end of the resistor R301 is connected with the first pin of the operational amplifier U301A and the third pin of the operational amplifier U327 respectively, the second pin of the operational amplifier U301A is connected with one end of the resistor R314 and one end of the resistor R322 respectively; the eighth pin of the operational amplifier U301A is connected with one end of the capacitor C559 and one end of the resistor R539 respectively, and the other end of the capacitor C559 is grounded, the fourth pin of the operational amplifier U301A is connected with one end of the capacitor C560 and one end of the resistor R540 respectively, and the other end of the capacitor C560 is grounded.

[0014] The utility model discloses a beneficial effect is:

[0015] 1. The utility model discloses a kind of current reference source circuits of high-precision DC resistance tester based on PGA280AIPWR, adjustable voltage can be output by chip, cooperate precision resistor module, make the voltage output by circuit have higher precision and stability, and circuit not only simple structure, easy to design and debug, can also output high-precision, low temperature drift constant voltage.

[0016] 2. The high-precision DC resistance tester current reference source circuit based on an operational amplifier, which can output two constant DC voltages with the same amplitude and adjustable amplitude and opposite directions, so that the constant current source can output constant and accurate current, greatly improving the resistance test accuracy, and through the control of the analog switch switching module, the two constant DC voltages with the same amplitude and opposite directions can be converted into one constant DC voltage or one frequency-controllable and amplitude-constant AC square wave voltage, and in combination with the precision resistance module, the operational amplifier and the precision low-temperature drift metal foil resistance constitute an inverting amplifier, realizing low-temperature drift and high-precision constant voltage output. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0018] Figure 1 is a principle block diagram of a current reference source circuit for a DC resistance tester according to an embodiment of the present application;

[0019] Figure 2 is a chip schematic diagram of a current reference source circuit for a DC resistance tester according to an embodiment of the present application;

[0020] Figure 3 is a switch control circuit schematic diagram of a current reference source circuit for a DC resistance tester according to an embodiment of the present application;

[0021] Figure 4 is a digital signal processing circuit schematic diagram of a current reference source circuit for a DC resistance tester according to an embodiment of the present application;

[0022] Figure 5 is a circuit schematic diagram of a precision resistance module of a current reference source circuit for a DC resistance tester according to an embodiment of the present application;

[0023] Figure 6 is a four-terminal measurement method equivalent block diagram of a current reference source circuit for a DC resistance tester according to an embodiment of the present application;

[0024] Figure 7 is a constant current source principle block diagram of a current reference source circuit for a DC resistance tester according to an embodiment of the present application.

[0025] In the drawings:

[0026] 1, single-chip microcomputer; 2, chip; 3, analog switch switching module; 4, precision resistance module; 5, constant voltage output module. DETAILED DESCRIPTION

[0027] To further illustrate the embodiments, the utility model provides the drawings, these drawings are part of the utility model disclosure, it mainly used to illustrate the embodiment, and can cooperate with the relevant description of the specification to explain the operating principle of the embodiment, cooperate with reference to these contents, the person skilled in the art should be able to understand other possible implementation ways and the advantages of the utility model, the components in the drawing are not drawn according to scale, and similar component symbols are usually used to represent similar components.

[0028] According to the embodiment of the utility model, a current reference source circuit for direct current resistance tester is provided.

[0029] The utility model will be further illustrated by combining with the specific embodiment and the drawing, as shown in Figure 1 The PGA280AIPWR-based high-precision direct current resistance tester current reference source circuit according to the embodiment of the utility model includes a single-chip microcomputer 1 for controlling output constant voltage; a chip 2 for outputting adjustable voltage; an analog switch switching module 3 for converting the chip 2 output voltage into constant direct current voltage according to the output signal; a precision resistance module 4 for realizing voltage amplitude adjustable function by adjusting resistance resistance value; a constant voltage output module 5 for outputting constant voltage according to the adjustment result of the precision resistance module 4; the output end of the single-chip microcomputer 1 is connected with the input end of the chip 2, the output end of the chip 2 is connected with the input end of the analog switch switching module 3, the output end of the analog switch switching module 3 is connected with the input end of the precision resistance module 4, and the output end of the precision resistance module 4 is connected with the input end of the constant voltage output module 5.

[0030] In one embodiment, the chip 2 includes a resistor R553, a capacitor C550, a diode D546, a diode D547, a resistor R554, a capacitor C551 and an operational amplifier U327; one end of the resistor R553 is connected with one end of the capacitor C550, one end of the diode D546, one end of the diode D547 and the eleventh pin of the operational amplifier U327 respectively, and the other end of the capacitor C550 and the other end of the diode D547 are both grounded; the sixth pin of the operational amplifier U327 is connected with one end of the resistor R554 and one end of the capacitor C551 respectively, and the other end of the capacitor C551 is grounded.

[0031] In one embodiment, the analog switch switching module 3 includes a digital signal processing circuit and a switch control circuit, wherein the output end of the digital signal processing circuit is connected with the input end of the switch control circuit, and the switch control circuit is connected with the precision resistance module 4 and the chip 2 respectively.

[0032] In one embodiment, the digital signal processing circuit includes diode D408, resistor R463, hex inverter U311 and capacitor C5019; the fourth pin of the hex inverter U311 is connected with the switch control circuit, the seventh pin, the ninth pin, the eleventh pin and the thirteenth pin of the hex inverter U311 are grounded, the first pin of the hex inverter U311 is connected with one end of the resistor R463 and the third pin of the diode D408 respectively, and the other end of the resistor R463 is grounded, the fourteenth pin of the hex inverter U311 is connected with one end of the capacitor C5019, and the other end of the capacitor C5019 is grounded.

[0033] In one embodiment, the switch control circuit includes analog switch U320D, analog switch U320A, resistor R314, resistor R322, capacitor C540 and capacitor C541; the eighth pin of the analog switch U320D is connected with the fourth pin of the hex inverter U31, the sixth pin of the analog switch U320D is connected with the first pin of the operational amplifier U327, the seventh pin of the analog switch U320D is connected with one end of the resistor R314, and the other end of the resistor R314 is connected with one end of the precision resistor module and one end of the resistor R322 respectively; the second pin of the analog switch U320A is connected with the second pin of the operational amplifier U327, the third pin of the analog switch U320A is connected with the other end of the resistor R322, the fourth pin of the analog switch U320A is connected with one end of the capacitor C540, and the other end of the capacitor C540 is grounded, the thirteenth pin of the analog switch U320A is connected with one end of the capacitor C541, the other end of the capacitor C541 is grounded, and the fifth pin of the analog switch U320A is grounded.

[0034] In one embodiment, the precision resistor module 4 includes resistor R8, resistor R301, resistor R540, capacitor R560, operational amplifier U301A, capacitor C559 and resistor R539; one end of the resistor R8 is connected with one end of the resistor R301 and the third pin of the operational amplifier U301A respectively, and the other end of the resistor R8 is grounded, the other end of the resistor R301 is connected with the first pin of the operational amplifier U301A and the third pin of the operational amplifier U327 respectively, the second pin of the operational amplifier U301A is connected with one end of the resistor R314 and one end of the resistor R322 respectively; the eighth pin of the operational amplifier U301A is connected with one end of the capacitor C559 and one end of the resistor R539 respectively, and the other end of the capacitor C559 is grounded, the fourth pin of the operational amplifier U301A is connected with one end of the capacitor C560 and one end of the resistor R540 respectively, and the other end of the capacitor C560 is grounded.

[0035] It needs to be explained that the chip 2 adopts PGA280AIPWR, which is a zero drift programmable gain amplifier, and can output two constant voltages with the same amplitude and opposite directions controlled by the single-chip microcomputer 1. Through the six inverter U311 with Schmidt trigger input and analog switches U320A and U320D, the two constant voltages with the same amplitude and opposite directions can be converted into a constant DC voltage or an AC square wave voltage with controllable frequency and constant amplitude, and then the constant adjustable voltage is output through the precision resistance module (composed of operational amplifier U301A, resistor R301 and resistor R8, and the voltage adjustable function can be realized by adjusting the resistance values of resistor R301 and resistor R8).

[0036] High-precision DC resistance tester is usually applied in research laboratories and precision manufacturing, which requires high testing precision. In order to meet the testing requirements and ensure the accuracy and reliability of the resistance test results, the current reference source must provide stable, accurate and less temperature-affected constant voltage.

[0037] Therefore, the current reference source (such as Figures 2 to 5 It needs to be explained that the connection between A in Figure 2 and A in Figure 3 , the connection between B in Figure 3 and B in Figure 4 , the connection between C and D in Figure 3 and C and D in Figure 5 ) selects the chip PGA280AIPWR and the precision resistance module 4. The single-chip 1 controls the chip PGA280AIPWR to output adjustable stable voltage. The six inverter U311 is a six inverter with Schmidt trigger input, and its four-pin output signal is given to the analog switch U320A and the analog switch U320D, so that the analog switch switches at a certain frequency, thereby converting the voltage output by the PGA280AIPWR into a constant DC voltage or an AC square wave voltage with controllable frequency and constant amplitude, which is input to the operational amplifier U301A. The resistance values of the feedback resistor R301 and the grounding resistor R8 of the operational amplifier U301A can be adjusted to realize the output voltage amplitude adjustable function. The resistor R301 and the resistor R8 are precision low-temperature drift non-inductive metal foil resistors, which can greatly reduce the voltage temperature drift and error in the transmission path, thereby improving the measurement accuracy of the tester.

[0038] Currently, the precision DC resistance measurement usually adopts the four-terminal measurement method (as shown in Figure 6 ), and the high-precision DC resistance tester is no exception. It is composed of a constant current source and a voltmeter inside. The constant current source provides a constant current applied to the two ends of the measured resistance, thereby forming a voltage drop across the resistance, which is then collected by the voltmeter. According to Ohm's law R=U / I (voltage collected by the voltmeter / constant current output by the constant current source), the resistance value of the measured resistance is calculated.

[0039] like Figure 7 As shown, the constant current source consists of a current reference source, an operational amplifier, a power output stage, and a feedback network. The current reference source provides a stable constant voltage as a reference for the output of the constant current source. The operational amplifier converts the reference current into an output current. Combined with the feedback network, the output voltage of the operational amplifier is adjusted by sampling the output current and comparing it with the reference current, thereby controlling the stability of the output current. The power output stage provides sufficient output power to drive the resistor under test.

[0040] In summary, by utilizing the above-mentioned technical solution of this utility model, a current reference source circuit for a DC resistance tester is proposed. Through chip 2, it can output an adjustable voltage. Combined with the precision resistor module 4, the circuit output voltage has high accuracy and stability. Furthermore, the circuit is not only simple in structure and easy to design and debug, but also outputs a high-precision, low-temperature-drift constant voltage. The current reference source circuit for a DC resistance tester provided by this utility model can output two constant DC voltages with the same and adjustable amplitudes but opposite directions. This allows the constant current power supply to output a constant and accurate current, greatly improving the accuracy of resistance testing. Simultaneously, by controlling the analog switch switching module, the two constant DC voltages with the same amplitude but opposite directions can be selected to convert into either a single constant DC voltage or a frequency-controllable, constant-amplitude AC square wave voltage. Combined with the precision resistor module, the operational amplifier and the precision low-temperature-drift metal foil resistor form an inverting amplifier, achieving a low-temperature-drift, high-precision constant voltage output.

[0041] In this utility model, unless otherwise explicitly specified and limited, the terms "installation", "setting", "connection", "fixing", "screw connection", etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0042] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A current reference source circuit for a direct current resistance tester, characterized by, The utility model relates to a constant voltage output circuit, including: a single-chip microcomputer for controlling constant voltage output; a chip for outputting adjustable voltage; an analog switch switching module for converting chip output voltage into constant direct current voltage according to output signal; a precision resistance module for realizing voltage amplitude adjustable function by adjusting resistance resistance value; a constant voltage output module for outputting constant voltage according to precision resistance module adjustment result; the output end of the single-chip microcomputer is connected with the input end of the chip, the output end of the chip is connected with the input end of the analog switch switching module, the output end of the analog switch switching module is connected with the input end of the precision resistance module, and the output end of the precision resistance module is connected with the input end of the constant voltage output module.

2. A current reference source circuit for a DC resistance tester according to claim 1, characterized in that, The chip includes resistance R553, capacitor C550, diode D546, diode D547, resistance R554, capacitor C551 and operational amplifier U327. One end of the resistance R553 is connected with one end of the capacitor C550, one end of the diode D546, one end of the diode D547 and the eleventh pin of the operational amplifier U327 respectively, and the other end of the capacitor C550 and the other end of the diode D547 are both grounded. The sixth pin of the operational amplifier U327 is connected with one end of the resistance R554 and one end of the capacitor C551 respectively, and the other end of the capacitor C551 is grounded.

3. A current reference source circuit for a DC resistance tester according to claim 2, wherein, The analog switch switching module includes a digital signal processing circuit and a switch control circuit, wherein the output end of the digital signal processing circuit is connected with the input end of the switch control circuit, and the switch control circuit is connected with the precision resistance module and the chip respectively.

4. A current reference source circuit for a DC resistance tester according to claim 3, wherein, The digital signal processing circuit includes diode D408, resistance R463, six-way inverter U311 and capacitor C5019. The fourth pin of the six-way inverter U311 is connected with the switch control circuit, the seventh pin, the ninth pin, the eleventh pin and the thirteenth pin of the six-way inverter U311 are all grounded, one end of the resistance R463 and the third pin of the diode D408 are connected with the first pin of the six-way inverter U311 respectively, and the other end of the resistance R463 is grounded, one end of the capacitor C5019 is connected with the fourteenth pin of the six-way inverter U311, and the other end of the capacitor C5019 is grounded.

5. A current reference source circuit for a DC resistance tester according to claim 4, wherein, The switch control circuit includes analog switch U320D, analog switch U320A, resistance R314, resistance R322, capacitor C540 and capacitor C541. The eighth pin of the analog switch U320D is connected with the fourth pin of the six-way inverter U31, the sixth pin of the analog switch U320D is connected with the first pin of the operational amplifier U327, one end of the resistance R314 is connected with the seventh pin of the analog switch U320D, and the other end of the resistance R314 is connected with one end of the precision resistance module and one end of the resistance R322 respectively. The second pin of the analog switch U320A is connected with the second pin of the operational amplifier U327, the third pin of the analog switch U320A is connected with the other end of the resistor R322, the fourth pin of the analog switch U320A is connected with one end of the capacitor C540, the other end of the capacitor C540 is grounded, the thirteenth pin of the analog switch U320A is connected with one end of the capacitor C541, the other end of the capacitor C541 is grounded, and the fifth pin of the analog switch U320A is grounded.

6. A current reference source circuit for a DC resistance tester according to claim 2, wherein, The precision resistor module comprises a resistor R8, a resistor R301, a resistor R540, a capacitor R560, an operational amplifier U301A, a capacitor C559 and a resistor R539. One end of the resistor R8 is connected with one end of the resistor R301 and the third pin of the operational amplifier U301A respectively, and the other end of the resistor R8 is grounded, the other end of the resistor R301 is connected with the first pin of the operational amplifier U301A and the third pin of the operational amplifier U327 respectively, the second pin of the operational amplifier U301A is connected with one end of the resistor R314 and one end of the resistor R322 respectively; The eighth pin of the operational amplifier U301A is connected with one end of the capacitor C559 and one end of the resistor R539 respectively, and the other end of the capacitor C559 is grounded, the fourth pin of the operational amplifier U301A is connected with one end of the capacitor C560 and one end of the resistor R540 respectively, and the other end of the capacitor C560 is grounded.

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