Digital measurement and control instrument of mechanical switch closing resistor

Abstract

The utility model relates to the technical field of industrial automation, in particular to a digital measurement and control instrument of a mechanical switch closing resistor. Comprising a power supply adjusting circuit module which is provided with a 24VDC power supply input end, and the 24VDC power supply input end is connected with a resettable fuse F1 through an anti-reverse diode D2 and then is connected with the input end of a switching power supply voltage adjusting chip U1. According to the utility model, the dynamic constant current source controlled by the high-precision DAC and the built-in 24b-it analog-to-digital converter of the NSA2860 chip are integrated, so that a multi-mode excitation current regulation and control mechanism is constructed. Based on real-time voltage drop signal analysis of an MCU, the system automatically triggers a relay to switch an excitation loop to a precise sampling resistor for online calibration, obtains a precise current value under current DAC output and stores calibration parameters, and cooperative control of nanoampere-level current resolution and milliohm-level resistance measurement is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to industrial automation technical field, concretely is a digital measuring and control instrument of mechanical type switch closing resistance. BACKGROUND

[0002] In the field of industrial automation and precision electronic manufacturing, the accurate detection of mechanical type switch closing resistance is the core index of evaluating contact reliability, contact loss and electrical performance. The current conventional resistance detection device usually adopts a fixed range constant current excitation mode, and the excitation current value and the resistance value range of the resistance to be detected are in a strong coupling relationship: a large current needs to be applied to obtain a distinguishable voltage drop signal for a small resistance of milliohm level, and a small current needs to be applied to avoid excessive heat dissipation for a large resistance of kiloohm level.

[0003] In the prior art, most devices use mechanical relays to switch discrete constant current sources to realize gear adjustment, but this method has three inherent defects: first, the current accuracy of the discrete constant current source is significantly affected by temperature drift and component aging, resulting in deterioration of linearity during cross-range measurement; second, the contact resistance of the mechanical relay introduces additional error, which cannot be ignored, especially in micro-ohm level measurement; third, the traditional scheme lacks a dynamic impedance matching mechanism, and cannot adaptively adjust the excitation current gear according to the real-time voltage drop signal of the measured resistance, making it difficult to optimize the measurement efficiency and accuracy simultaneously. How to build a closed-loop measurement and control system with wide-range impedance adaptive matching capability has become the key to breaking through the current technical bottleneck. UTILITY MODEL CONTENTS

[0004] The utility model provides a digital measuring and control instrument of mechanical type switch closing resistance to solve the problems of insufficient cross-range measurement accuracy, poor dynamic adaptability and system error accumulation of the existing mechanical type switch closing resistance detection device in wide resistance value range (milliohm to kiloohm level) measurement due to the inherent defects of fixed excitation current mode and discrete gear switching structure.

[0005] The technical solution of the utility model to solve the above technical problems is as follows:

[0006] A digital measuring and control instrument of mechanical type switch closing resistance is provided, comprising:

[0007] A power supply adjustment circuit module is provided with a 24VDC power supply input end, which is connected to the input end of a switching power supply voltage regulating chip U1 after passing through an anti-reverse diode D2 and connecting a self-restoring fuse F1. The output end of the switching power supply voltage regulating chip U1 generates an 8V power supply through an LC filter circuit and is connected to a digital voltage stabilizing chip U2 and an analog voltage stabilizing chip U3 in parallel, respectively generating 5VC digital power supply and 5VA analog power supply which are isolated from each other;

[0008] MCU minimum system module, including single-chip microcomputer U10, its P0.5-P00.7 pin connects the SPI interface of digital tube drive chip U7, P1.1-P1.4 pin is directly connected with independent key K1-K4, P3.0 pin is connected with the control coil of multi-position switching relay JD3 through relay drive circuit, P0.3-P0.4 pin is connected with output relay JD1-JD2 through photoelectric isolation circuit;

[0009] AD sampling and multi-position excitation current generating module, including chip U9, its SPI interface is connected with the SPI bus of the single-chip microcomputer U10 through four-bit resistor RP3, the 16-bit DAC output end of the chip U9 is connected with constant current source circuit composed of operational amplifier, the output end of the constant current source circuit is connected with precision sampling resistor R10 or resistance interface P2 selected and connected through relay JD3 switching;

[0010] Keyboard display module, including six digital tube arrays, the digital tube segment selection line is connected with the single-chip microcomputer U10 through drive chip U7, and the bit selection line is pulled up to 5VC power supply through resistor RP1-RP2;

[0011] Output control circuit module, provided with two independent photoelectric isolation circuits U5-U6, the input end of the photoelectric isolation circuits U5-U6 is connected with the P0.3-P0.4 pin of the single-chip microcomputer U10 respectively, and the output end of the photoelectric isolation circuits U5-U6 drives the coil loop of relay JD1-JD2 respectively.

[0012] Further, the switching power supply voltage regulating chip U1 adopts TPS5430 chip, the VIN pin of the TPS5430 chip is connected with 24V input positive pole through inductor L1, the PH pin is filtered through the parallel connection of capacitor C1-C3 and inductor L2 and then outputs 8V voltage, the digital voltage stabilizing chip U2 adopts LM7805, and the analog voltage stabilizing chip U3 adopts LM7905, and 0Ω resistor R3-R4 is connected between 5VC and 5VA power supply ground.

[0013] Further, the reset circuit of the single-chip microcomputer U10 includes series-connected resistor R16 and capacitor C15, the XTAL1-XTAL2 pin of the single-chip microcomputer U10 is externally connected with 12MHz crystal oscillator Y1 and matching capacitor C16-C17, the ISP programming interface P1 includes TXD, RXD and RST signal lines, and the common end of the four-bit resistor RP3 is connected with 5VC power supply.

[0014] Further, the constant current source circuit is composed of operational amplifier U9B, the noninverting input end of the operational amplifier U9B is connected with the DAC output end, the inverting input end is connected with current output node through resistor R7, and the output end drives current loop through MOS tube Q1, and the precision sampling resistor R10 is 50mΩ / 1% precision metal film resistor.

[0015] Further, the P3.0 pin of the single-chip microcomputer U10 is connected to the base of the triode Q2 through the resistor R12, the collector of the triode Q2 is connected to one end of the control coil, the other end of the control coil is connected to a 5VC power supply, the normally open contact of the relay JD3 is connected to the precision sampling resistor R10, and the normally closed contact is connected to the resistance interface P2 to be measured.

[0016] Further, the driving chip U7 adopts a TM1629 chip, the SEG0-SEG15 pins of which are connected to the segment selection lines of the nixie tube through the row resistor RP1, the GRID1-GRID6 pins of which are connected to the digit selection lines of the nixie tube through the row resistor RP2, and the independent keys K1-K4 are connected to the 5VC power supply through the pull-up resistors R18-R21 respectively.

[0017] Further, the optocoupler isolation circuit U5-U6 adopts a PC817 chip, the input end anode of which is connected to the P0.3-P0.4 pins of the single-chip microcomputer U10 through the resistors R22-R23, the cathode is grounded, the output end collector is connected to the coils of the relays JD1-JD2, and the emitter is grounded through the freewheeling diodes D4-D5.

[0018] Further, the adaptive gear adjustment program is arranged in the MCU minimum system module, when it is detected that the voltage at the end of the resistance to be measured exceeds the ADC range of the NSA2860, the relay JD3 is automatically controlled to switch to the calibration mode, the DAC output value is adjusted to change the excitation current gear, and the system is switched back to the measurement mode until the sampling voltage is in the range of 20%-80% of the range.

[0019] The utility model discloses the beneficial effect is:

[0020] The utility model discloses a high-precision DAC control's dynamic constant current source and the 24b it analog-digital converter built -in of NSA2860 chip are integrated, and a multimodal excitation current regulation mechanism is constructed. Based on the real -time voltage drop signal analysis of MCU, the system automatically triggers the relay to switch the excitation circuit to the precision sampling resistance and carries out online calibration, obtains the accurate current value under the current DAC output and stores the calibration parameter, realizes the collaborative control of nanometer ampere level current resolution and milliohm level resistance measurement. The magnetic bead isolation design of digital and analog ground in the power supply adjustment module, in combination with the cascade protection of self -restoring fuse and anti -reversal diode, effectively suppresses the influence of common mode interference on weak signal acquisition. Through dynamic impedance matching algorithm, the system can complete the gear optimization selection of excitation current in a single measurement period, so that the voltage drop at the two ends of the resistance to be measured is always in the best quantization interval of ADC, thereby realizing the stable measurement of 0.5% relative accuracy in the wide resistance domain range, and avoiding the efficiency loss caused by manual intervention and the systematic error caused by contact oxidation in the traditional scheme. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a whole structure block diagram of the utility model;

[0022] Figure 2 is a power supply adjusting circuit of the utility model;

[0023] Figure 3 is an MCU minimum system circuit of the utility model;

[0024] Figure 4 is an AD sampling and multi-gear excitation current generating circuit of the utility model;

[0025] Figure 5 is a keyboard display circuit of the utility model;

[0026] Figure 6 is an output control circuit of the utility model. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the utility model more clear and obvious, the utility model is further explained in detail below by combining with the drawings and examples. The examples of the examples are shown in the drawings, wherein the same or similar signs represent the same or similar elements or elements with the same or similar functions throughout. The examples described below by referring to the drawings are exemplary and are only used to explain the utility model, and cannot be understood as limiting the utility model. In addition, it should be understood that the specific examples described herein are only used to explain the utility model, and are not used to limit the utility model.

[0028] In the description of the utility model, it should be pointed out that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, can also be detachable connection, or integrally connected, can be mechanical connection, can also be electrical connection or can communicate with each other, can be directly connected, can also be indirectly connected through intermediate medium, can be the communication or interaction relationship between two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0029] The disclosure below provides many different embodiments or examples for implementing various aspects of the present application. Although each of the various embodiments described below with respect to the present application is preferred, the application is not limited to any particular embodiment described. The disclosure below provides many different embodiments or examples for implementing various aspects of the present application. In order to simplify the present application, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art can realize the application of other processes and / or the use of other materials.

[0030] The present application provides the following preferred embodiments:

[0031] In order to solve the problem of insufficient adaptive adjustment of excitation current and weak interference suppression between multiple circuit modules in the mechanical switch closing resistance measurement process, the present embodiment provides a high-precision, strong anti-interference digital measurement and control instrument for mechanical switch closing resistance. The present embodiment is based on the optimization design of sub-module circuit, and realizes the accurate measurement and control of wide range resistance through power isolation, signal conditioning and adaptive control strategy.

[0032] Further, Figure 1 The structure diagram of the measurement and control instrument is shown in the figure. The measurement and control instrument is powered by 24VDC commonly used in industry, and the power supply is output to the system through the power supply adjustment module. With high cost performance MCU as the core, equipped with 6 digit display, independent keyboard for system parameter input. The current source for exciting the measured resistance is generated by the 16b it analog-to-digital converter inside NSA2860 in cooperation with the constant current circuit, and the multi-gear excitation current is generated through the MCU to control the relay in the multi-gear current control module to switch the excitation current into a precision sampling resistance. The 24bit high-precision analog-to-digital converter in NSA2860 collects the terminal voltage of the sampling resistance to convert the size of the excitation current, and the different digital quantities recorded in the input DAC can obtain the size of the excitation current of multiple gears to match the measurement of different resistance gears. According to the resistance value range of the measured resistance, the corresponding excitation current is selected, and in the normal detection resistance mode, the terminal voltage of the measured resistance is converted by ADC and the conversion result is obtained by MCU, and the resistance value of the measured resistance is converted according to the size of the excitation current at this time. MCU sends out corresponding control signals according to the detected resistance value.

[0033] Further, Figure 2The power supply regulating circuit of the measuring and controlling instrument is shown in Fig. 2. U1 is a TPS5430 chip, which is a high-efficiency switching power regulating chip. The 24V DC power supply is regulated by the chip U1 and LC filter to generate 8V power supply. U2 and U3 are voltage stabilizing chips, which generate 5V digital power supply 5VC and 5V analog power supply 5VA, respectively, to supply power to the digital circuit and analog circuit of the system. D2 is a reverse prevention diode, and F1 is a self-recovery fuse. The 0-ohm resistors R3 and R4 are used to isolate different reference grounds to prevent mutual interference between different types of circuits.

[0034] Further, Figure 3 The minimum system of the MCU is shown in Fig. 3. R16 and C15 generate a reset signal for the single-chip microcomputer U10. U10 is a high-speed 51 single-chip microcomputer, which has a rich set of internal resources. The single-chip microcomputer communicates with the NSA2860 through the SPI bus. The P0.5-P0.7 pins of U10 control the digital tube driving chip. The four independent keys are directly connected to the P1.1-P1.4 pins of the single-chip microcomputer. RP3 is a four-bit resistor array, which is used for SPI bus logic level matching between the single-chip microcomputer and the NSA2860 to reduce noise during communication. The switching excitation current circuit relay for multi-range current generation is controlled by P3.0. The control signals of the two-way switch control relay are controlled by P0.3 and P0.4 of the single-chip microcomputer. P1 is an ISP interface, through which the simulation debugging and program downloading functions of the single-chip microcomputer can be realized.

[0035] Further, Figure 4 The AD sampling and multi-range excitation current generating circuit is shown in Fig. 4. NSA2860 is a chip with 24-bit ADC and 16-bit DAC integrated inside, which has a high cost performance. The internal DAC generates a voltage output after receiving the corresponding digital quantity from the MCU, and then the constant current source circuit composed of U9 and peripheral resistors generates an excitation current source. P2 is the interface of the resistance to be measured. When the excitation current flows through the resistance to be measured, the terminal voltage V-Det is generated and sent to the analog input terminal of NSA2860 for conversion by the internal ADC. The conversion result is obtained by the MCU and the size of the resistance to be measured is calculated after conversion. When the multi-range excitation current source is needed, the micro-relay JD3 is controlled by the P3.0 pin of the single-chip microcomputer to switch the excitation current to the precision sampling resistor R10. The excitation current is generated by the internal DAC and constant current circuit of NSA2860, and the terminal voltage V-Det of the precision sampling resistor is converted by the internal ADC. The conversion result is read by the MCU, the excitation current size is calculated according to V / R, the input digital quantity of the DAC is changed, and the different excitation current of different ranges is obtained by saving in the FLASH memory of the MCU. Then, the relay JD3 is controlled to be powered off to restore to the normal resistance detection mode.

[0036] It can be understood that when the normal detection resistance, MCU according to the real-time conversion value of the acquisition ADC, according to the conversion value to determine whether to replace the excitation current gear and the gain of ADC, so as to realize the adaptive adjustment of different orders of magnitude to be measured resistance.

[0037] Further, Figure 5 The keyboard display circuit is mainly used for man-machine interaction, six nixie tubes are used for displaying resistance value and the like information, RP1 and RP2 in the figure are resistors, U7 is a special nixie tube driving chip, U7 and the single-chip microcomputer communicate through a synchronous serial interface.

[0038] Further, Figure 6 The output control circuit is provided with two-way switch control signals, and the system sends corresponding control signals according to different resistance value measurement results.

[0039] The utility model discloses beneficial effect specifically embodied above only for the preferred embodiment of the utility model, and not with the restriction of the utility model, any modification, equivalent replacement, improvement and the like made in the spirit and principles of the utility model should be contained in the protection scope of the utility model.

Claims

1. A digital control instrument for mechanical switch closing resistance, characterized in that, It includes: The power supply regulating circuit module is provided with a 24VDC power input end, is connected to the input end of a switching power supply voltage regulating chip U1 after a self-recovery fuse F1 through an anti-reverse diode D2, the output end of the switching power supply voltage regulating chip U1 generates an 8V power supply through an LC filter circuit and is connected to a digital voltage stabilizing chip U2 and an analog voltage stabilizing chip U3 in parallel, and 5VC digital power supply and 5VA analog power supply which are isolated from each other are generated respectively; The MCU minimum system module includes a single-chip microcomputer U10, the P0.5-P0.7 pins of which are connected to the SPI interface of a digital tube driving chip U7, the P1.1-P1.4 pins are directly connected to independent keys K1-K4, the P3.0 pin is connected to the control coil of a multi-position switching relay JD3 through a relay driving circuit, and the P0.3-P0.4 pins are connected to output relays JD1-JD2 through an optical isolation circuit. The AD sampling and multi-position excitation current generating module includes a chip U9, the SPI interface of which is connected to the SPI bus of the single-chip microcomputer U10 through a four-bit resistor RP3, the 16-bit DAC output end of the chip U9 is connected to a constant current source circuit composed of an operational amplifier, and the output end of the constant current source circuit is connected to a precision sampling resistor R10 or a to-be-measured resistor interface P2 selected by the switching of the relay JD3. The keyboard display module includes a six-digit digital tube array, the digital tube segment selection line of which is connected to the single-chip microcomputer U10 through the driving chip U7, and the bit selection line is pulled up to the 5VC power supply through resistors RP1-RP2. The output control circuit module is provided with two independent optical coupling isolation circuits U5-U6, the input ends of which are connected to the P0.3-P0.4 pins of the single-chip microcomputer U10 respectively, and the output ends of which drive the coil loop of the relays JD1-JD2 respectively.

2. The digital instrument for measuring and controlling the resistance of a mechanical switch according to claim 1, characterized in that, The switching power supply voltage regulating chip U1 adopts a TPS5430 chip, the VIN pin of which is connected to the 24V input positive pole through an inductor L1, the PH pin is filtered through the parallel connection of capacitors C1-C3 and an inductor L2 and outputs an 8V voltage, the digital voltage stabilizing chip U2 adopts an LM7805, and the analog voltage stabilizing chip U3 adopts an LM7905, and 0Ω resistors R3-R4 are connected in parallel between the 5VC and 5VA power supply grounds.

3. The digital instrument for measuring and controlling the resistance of a mechanical switch according to claim 1, characterized in that, The reset circuit of the single-chip microcomputer U10 includes a resistor R16 and a capacitor C15 connected in series, the XTAL1-XTAL2 pins of the single-chip microcomputer U10 are externally connected to a 12MHz crystal oscillator Y1 and matching capacitors C16-C17, the ISP programming interface P1 includes TXD, RXD and RST signal lines, and the common end of the four-bit resistor RP3 is connected to the 5VC power supply.

4. The digital instrument for measuring and controlling the resistance of a mechanical switch according to claim 1, characterized in that, The constant current source circuit is composed of an operational amplifier U9B, the non-inverting input end of which is connected to the DAC output end, the inverting input end is connected to a current output node through a resistor R7, the output end drives a current loop through a MOS transistor Q1, and the precision sampling resistor R10 is a 50mΩ / 1% precision metal film resistor.

5. The digital instrument for measuring and controlling the resistance of a mechanical switch according to claim 1, characterized in that, The P3.0 pin of the single-chip microcomputer U10 is connected to the base of the triode Q2 through the resistor R12, the collector of the triode Q2 is connected to one end of the control coil, the other end of the control coil is connected to a 5VC power supply, the normally open contact of the relay JD3 is connected to the precision sampling resistor R10, and the normally closed contact is connected to the resistance interface P2 to be measured.

6. The digital instrument for measuring and controlling the resistance of a mechanical switch according to claim 1, characterized in that, The driving chip U7 adopts a TM1629 chip, the SEG0-SEG15 pins of which are connected to the digit tube segment selection line through the row resistor RP1, the GRID1-GRID6 pins of which are connected to the digit tube bit selection line through the row resistor RP2, and the independent keys K1-K4 are respectively connected to the 5VC power supply through the pull-up resistors R18-R21.

7. The digital instrument for measuring and controlling the resistance of a mechanical switch according to claim 1, characterized in that, The optocoupler isolation circuit U5-U6 adopts a PC817 chip, the input end anode of which is connected to the P0.3-P0.4 pins of the single-chip microcomputer U10 through the resistors R22-R23, the cathode is grounded, the output end collector is connected to the relay JD1-JD2 coil, and the emitter is grounded through the freewheeling diodes D4-D5.

8. The digital instrument for measuring and controlling the resistance of a mechanical switch according to claim 1, characterized in that, The MCU minimum system module is provided with an adaptive gear adjustment program, when it is detected that the voltage at the end of the resistance to be measured exceeds the ADC range of the NSA2860, the relay JD3 is automatically controlled to switch to the calibration mode, the excitation current gear is changed by adjusting the DAC output value, and after the sampling voltage is in the range of 20%-80% of the range, the measurement mode is switched back.

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