CN104181488A - AC voltage-resistant testing apparatus - Google Patents

Abstract

The invention discloses an AC withstand voltage testing device, which samples the voltage from a withstand voltage instrument through a voltage sampling circuit, sends the sampled voltage to a metering device, and the metering device transmits the data to a hybrid processor, and the hybrid processor converts the data It is displayed on the display unit; the voltage sampling circuit adopts the principle of resistive voltage division, and multiple resistors are connected in series, and the two ends of each resistor in the last two resistors are connected in parallel with the corresponding capacitor. The device realizes the accurate measurement of the withstand voltage instrument for the first time, and the measurement voltage is high. The test voltage range of the device of the present invention is 1000-5000V. The device has high accuracy. The voltage display retains two decimal places, the accuracy reaches 0.1%, and the leakage current range is 0.05mA-0.25mA.

Description

AC withstand voltage test device

technical field

The invention relates to an AC withstand voltage testing device for high voltage measurement.

Background technique

The withstand voltage tester is a measuring instrument, which is mainly used for the testing of electric meters, collectors, terminals and other equipment between power companies and between power supply companies and users. , terminal and other equipment accuracy is an important part. In order to ensure that the on-site test work is carried out accurately and smoothly, the AC withstand voltage test device is particularly important.

At present, there is no accurate measuring instrument for testing the voltage withstand tester in the world and at home, and the AC withstand voltage test item is one of the strong inspection items of the electric energy meter, so higher requirements are put forward for the accuracy of the AC withstand voltage tester, so a design is made It is particularly important to accurately measure the AC withstand voltage test device of the withstand voltage instrument, and at the same time, it can meet the potential market demand of the AC withstand voltage test device.

Contents of the invention

In order to solve the deficiencies in the prior art, the invention discloses an AC withstand voltage test device, which solves the problem that the accuracy of the withstand voltage instrument cannot be judged in the current withstand voltage test process of the electric energy meter, and the accuracy of the test device reaches 0.1%. The design of the device is simple, intuitive, and portable, which is convenient for the operator to connect, test, and read data, and can greatly improve the reliability and accuracy of the withstand voltage test.

To achieve the above object, the specific scheme of the present invention is as follows:

The AC withstand voltage test device samples the voltage from the withstand voltage instrument through the voltage sampling circuit, and the sampled voltage is sent to the metering device, and the metering device transmits the data to the hybrid processor, and the hybrid processor displays the data on the display unit It is shown on the above; the voltage sampling circuit adopts the principle of resistance voltage division, and multiple resistors are connected in series, and the last two resistors are connected in parallel with the corresponding capacitors and then grounded;

The voltage sampling circuit is connected to the V2N/V2P voltage channel of the metering device, and the high-voltage signal from the withstand voltage instrument is converted into an AC signal with an amplitude of 0-1V through the voltage sampling circuit by using the complete differential input mode of the metering device. It is sent to the metering device through the voltage channel.

When the test device is powered on or the metering device is disturbed and reset, the hybrid processor updates the calibration data through the SPI port; the SIG signal is a handshake signal used to notify the hybrid processor, so the hybrid processor monitors the SIG signal , in order to enable the metering device to perform SPI operation synchronously with the hybrid processor after power-on and reset, the reset process keeps the RESET signal greater than 20us low level, the chip is reset, at this time SIG outputs high level, and then the hybrid processor will reset RESET The signal is pulled high, after the set time, the metering device is initialized, the SIG outputs a low level signal, and then the SPI operation is performed.

Both the RESET port of the metering device and the SIG input port of the hybrid processor are connected with decoupling capacitors.

The hybrid processor is also connected with an infrared communication unit, a display unit, a storage unit, a clock circuit, a keyboard and a battery.

The metering device communicates with the mixing processor through an SPI interface.

The storage unit includes a storage chip AT24LC256 and a Flash memory AT45DB161D for storing data.

The infrared communication unit includes an infrared receiving unit, an infrared sending unit and an infrared wake-up unit.

The initial state of the infrared communication unit/CVIR is at a high level. When an external infrared signal is irradiated, the photosensitive diode V8 receives the light signal and conducts, the base of the triode V10 is at a high level, the triode V10 conducts, and the IR-R becomes Low level, at this time, the hybrid processor controls the /CVIR pin to be low level, open the receiving tube VI pin, VIR becomes high level, receives the optical signal, sends it out after modulation and demodulation, and the IR-T pin Controlled by a hybrid processor, generating PWM.

The outside of the test device also includes an insulating shell.

This device uses the principle of resistance voltage division to sample the voltage from the withstand voltage instrument (1000V-5000V). The sampling voltage is sent to the metering chip ATT7026E through the resistance voltage division circuit. ATT7026E communicates with MSP430F5438 through the SPI interface. LCD display.

The voltage of the external withstand voltage instrument is connected through the terminal of the device shell. When the withstand voltage instrument starts to work, the test device measures the output voltage of the withstand voltage instrument through the metering circuit and displays it through the liquid crystal.

The hybrid processor communicates with ATT7026E through the SPI interface. ATT7026E measures the sampling voltage through the sampling circuit, and the measurement value is displayed on the LCD screen. The sampling circuit uses the principle of resistor voltage division to store data through the memory chip AT24LC256 and Flash memory AT45DB161D , when the CPU is in a low power consumption state, the meter can be woken up by infrared, and the test record and time can be read. At the same time, the infrared receiving tube HM238RL-W is used for communication to perform operations such as meter calibration. You can also press the button to wake up the device and flip the screen up and down.

The high-voltage signal (1000V-5000V) sent by the withstand voltage instrument is divided into 0-1V by the voltage sampling circuit and sent to the metering chip control circuit 2 through the V2N/V2P pin, V2N/V2P Positive and Negative Analog Input Pins for Voltage Channels. Completely differential input mode, the maximum input Vpp in normal operation is ±1.5V, there are ESD protection circuits inside the two pins, the maximum withstand voltage is ±6V, the voltage value collected by the metering chip is sent to the MCU chip through the SPI serial communication interface In the control circuit 3, the SPI interface of the metering chip works in a slave mode, using 2 control lines and 2 data lines: CS, SCLK, DIN and DOUT. The MCU control circuit 3 displays the collected voltage value on the withstand voltage instrument through the LCD display circuit 6. When the infrared wake-up is required, the infrared communication circuit 5 is started. The infrared communication uses the integrated infrared receiver IRM3638L as the receiving tube. The high-efficiency IR7393C is used as the emission tube. The data of each withstand voltage test is stored in the memory as an event. The event includes the time of the test, the maximum voltage value, and the duration, and can be displayed on a split screen. Storage circuit 7 includes serial E2PROM and FLASH memory, serial EEPROM, storage capacity is 256Kbit, it adopts I2C interface to communicate with MCU. The withstand voltage test device generally works in a low power consumption state, and it is only necessary to wake up the CPU and turn on the power supply circuit when performing the withstand voltage test. It is powered by battery, the battery voltage is input by VIN, the enable terminal EN is set high, and it is reduced to 5V after the linear step-down chip LDO, reaching the working voltage of the CPU.

The working principle of the AC withstand voltage test device: the high voltage signal generated by the withstand voltage instrument is collected through the resistor divider circuit, and sent to the metering chip for metering. The metering chip communicates with the MCU through the SPI interface. The metering chip is a high-precision three-phase active and reactive power ATT7026E special metering chip for electric energy. ATT7026E integrates six channels of second-order Σ-ΔADC, reference voltage circuit and all power, energy, effective value, power factor and digital signal processing circuits for frequency measurement. ATT7026E can measure the active power, reactive power, apparent power, active energy and reactive energy of each phase and combined phase, and can also measure the parameters of each phase current, voltage effective value, power factor, phase angle, frequency, etc. Fully meet the needs of three-phase multi-rate multi-function electric energy meter. ATT7026A supports two methods of resistance network calibration and software calibration. Resistance network meter calibration is suitable for system applications where the voltage channel uses resistance network sampling. By simply adjusting the resistance network, the system error can be corrected within the requirements of the level 1 meter. The software calibration is to compensate the gain and phase through the relevant calibration registers, which can correct the system error within the requirements of the 0.5 level meter. Active and reactive frequency calibration outputs CF1 and CF2 provide instantaneous active and reactive power information, which can be directly connected to the standard meter for error correction. The voltage monitoring circuit inside the ATT7026E can ensure normal operation when power is on and off. ATT7026E contains a (AVcc) power supply monitoring circuit on-chip, which continuously monitors the analog power supply incoming line. When the supply voltage is lower than 4V±5%, the chip will be reset. This is conducive to the correct startup and normal operation of the chip when the circuit is powered on and powered off. The power supply monitoring circuit is arranged in the delay and filtering links, which prevents errors caused by power supply noise to the greatest extent. In order to ensure the normal operation of the chip, the power supply should be decoupled so that the fluctuation of AVcc does not exceed 5V±5%.

Infrared communication uses infrared as the medium to transmit data information, and the infrared receiver and infrared transmitter complete the wireless transmission and reception of signals. At the transmitting end, after proper encoding and modulation, the sent digital signal is sent to the electro-optical conversion circuit, which drives the infrared diode to emit infrared light pulses. At the receiving end, the infrared receiver performs photoelectric conversion on the received infrared signal and performs After modulation and decoding, the original signal is restored. The infrared transmitting circuit is composed of a modulation circuit, a driving circuit and an infrared transmitting device, and the infrared receiving circuit is composed of an infrared receiving device, a preamplifying circuit, and a demodulating circuit.

Infrared communication is easily restricted and interfered by environmental conditions, and the use of high-power infrared emitting tubes or receivers with optical filters can greatly improve the anti-interference ability of communication. The design of this device uses the high-efficiency IR7393C as the transmitting tube, and the integrated infrared receiver IRM3638L as the receiving tube. Among them, the optical power of IR7393C reaches 150mW, which can effectively enhance the anti-interference ability of infrared communication; The role of the detection output.

The E2PROM used in this program adopts AT24LC256 of ATMEL Company, the Flash adopts AT45DB161D Flash memory of ATMEL Company, the clock chip is RX-8205 of EPSON Company, and the LCD liquid crystal is HQ71291-01 (high durability).

Beneficial effects of the present invention:

When the traditional three-phase electric meter is used for the withstand voltage test, the error of the withstand voltage instrument is relatively large, and the accuracy is not high, and it is impossible to accurately measure the withstand voltage value of the three-phase electric meter. The withstand voltage test is one of the mandatory inspection items of the electric energy meter experiment, so Hipot testing requires precise measurements. The invention adopts a high-precision measurement and sampling chip, and within the input dynamic working range (1000:1), the non-linear measurement error is less than 0.1%. The measurement is accurate, the withstand voltage event can be queried, and 10 withstand voltage events can be saved, and the collected data is more reliable.

1. For the first time, this device realizes the accurate measurement of the withstand voltage instrument, and the measurement voltage is high. The test voltage range of the device of the present invention is 1000-5000V.

2. The device has high accuracy. The voltage display retains two decimal places, the accuracy reaches 0.1%, and the leakage current range is 0.05mA-0.25mA.

3. The data of the withstand voltage experiment is stored in the event through the memory. The event includes the time of the experiment, the maximum voltage value, and the duration, which can be displayed on a split screen.

4. The power supply of the device is simple, it adopts battery power supply, the power consumption is small, about 8mA, and it can record more than 10,000 withstand voltage tests.

5. The design of the device is light, simple and intuitive, and has a good prospect for application and promotion.

Description of drawings

Fig. 1 is the block diagram of working principle of voltage withstand test device of the present invention;

Fig. 2 is a resistor divider sampling circuit;

Figure 3 metering chip ATT7026E unit;

Figure 4 is the MCU unit MSP430F5438;

Fig. 5 is an infrared communication unit;

Figure 6 liquid crystal display circuit;

Figure 7 storage unit;

Figure 8 power supply circuit;

Figure 9 clock circuit;

In the figure, 1 high-voltage input signal, 2 voltage sampling circuit, 3 metering chip ATT7026E, 4 MCU unit, 5 infrared communication unit, 6 display unit LCD, 7 storage unit, 8 clock circuit, 9 keys, 11 LDO chip, 12 battery.

Detailed ways:

The present invention is described in detail below in conjunction with accompanying drawing:

As shown in Figure 1, in the AC withstand voltage test device, the high voltage input signal 1 of the AC withstand voltage instrument is transmitted to the voltage sampling circuit 2, and the voltage sampling circuit 2 performs voltage sampling on the high voltage input signal 1, and the voltage sampling circuit 2 converts the sampled signal Send to the metering chip ATT7026E3, the metering chip ATT7026E3 performs metering processing on the received signal and then sends it to the MCU unit 4, MSP430F5438, the MCU unit 4 displays the data on the display unit LCD6, and the MCU unit 4 is also connected to the button 9 for receiving the button 9 Instructions for operation, the MCU unit 4 also communicates with the infrared communication unit 5 , the storage unit 7 and the clock circuit 8 , the MCU unit 4 and the metering chip ATT7026E3 are connected to the LDO chip 11 , and the LDO chip 11 is connected to the battery 12 .

The voltage sampling circuit converts the collected high-voltage signal of the withstand voltage instrument into a low-voltage signal, and sends it to the metering chip. The metering chip communicates through the control chip, and the collected voltage value is displayed through the liquid crystal circuit. Events are stored through the memory chip E2PROM circuit, and the power supply circuit includes a linear voltage regulator LDO chip, and the LDO chip is turned on during work.

The V2N/V2P voltage channel of the metering chip is adopted, and the full differential input method is used. The high-voltage signal from the withstand voltage instrument is converted into an AC signal with an amplitude of 0-1V through a resistor divider circuit, and sent to the metering chip through the voltage channel. The ADC of the metering chip is 16 bits, and the sampling rate of the ADC can reach 3.2KHZ. It can accurately collect the high-voltage signal output by the withstand voltage instrument, with an error of 0.1%. At the same time, it can record the duration of the high-voltage signal. The sampling speed of the metering chip is very fast, and the duration record is complete. High-voltage events are saved through the memory chip.

During the test, the output of the high-voltage side of the AC withstand voltage meter is connected to the strong current terminal of the test device, and the output of the low-voltage side of the AC withstand voltage meter is connected to the weak current terminal of the test device.

This device uses the principle of resistance voltage division to sample the voltage from the withstand voltage instrument (1000V-5000V). The sampling voltage is sent to the metering chip ATT7026E through the resistance voltage division circuit. ATT7026E communicates with MSP430F5438 through the SPI interface. LCD display.

Figure 2 is a resistance voltage sampling circuit, using the principle of resistance division, 67 300K resistors (20.1M) are connected in series, and the voltage channel in this device uses two pins V2P/V2N in ATT7026E. The sampling voltage range of the chip is 0-1V, the sampling voltage is 0.25V when the external high voltage is 5000V, and the sampling voltage is 0.05V when the external voltage is 1000V, all within the sampling range. To connect multiple resistors in series, one is to consider the influence of the temperature drift of the resistors, and the other is to consider the voltage division of the resistors. The resistors selected in this paper are below 15ppm to ensure the measurement accuracy.

Figure 3 metering chip ATT7026E unit, ATT7026E is a high-precision three-phase active and reactive energy dedicated metering chip, ATT7026E integrates six second-order Σ-ΔADC, reference voltage circuit and all power, energy, effective value, power factor and frequency measurement digital Signal processing and other circuits. There are 6 wires between ATT7026E and MCU, 4 of which are SPI communication interface lines CS, SCLK, DIN, DOUT, a reset control line of ATT7026E, and a handshake signal line SIG. ATT7026E provides an SPI interface to facilitate the transfer of metering parameters and calibration parameters with an external MCU.

ATT7026E itself has a very complete verification method for SPI reading and writing, but it also needs to strengthen the anti-interference ability of the signal line. Therefore, the connection line of the SPI communication interface should be as short as possible in the design. In order to prevent the SPI transmission signal from being interfered, it should be Wrap it with ground wire around it. In order to eliminate the high-frequency interference of the received signal, a 10Ω resistor can be connected in series on the SPI signal line, and a decoupling capacitor can be added to the signal input end, which can approximately form a low-pass filter, and the decoupling capacitor can be selected appropriately. Some, in order to enhance the anti-interference ability. In the SPI interface, the series resistors and capacitors of CS, SCLK, and DIN should be as close as possible to the ATT7026E chip, and the series resistors and capacitors of the DOUT terminal should be close to the MCU.

When the power is turned on or the ATT7026E is disturbed and reset, the external MCU must update the calibration data through the SPI port to ensure the accuracy of the measurement. The SIG signal is a handshake signal used to notify the external MCU, so the MCU must update the SIG signal. to monitor. In order to enable ATT7026E to perform SPI operation synchronously with the MCU after power-on and reset, the reset process must keep the RESET signal at a low level greater than 20us, the chip is reset, at this time SIG outputs a high level, and then the MCU pulls the RESET signal high, about After 500us, ATT7026E completes the initialization, and SIG outputs a low-level signal. After this process, SPI operation can be performed. In order to enhance the anti-interference ability, a 0.1uF decoupling capacitor should be connected to the RESET port and the SIG input port of the MCU.

Figure 4 shows the MCU unit MSP430F5438. As the core control chip, the MSP430 series microcontroller is a 16-bit ultra-low power microcontroller launched by Texas Instruments (TI). Because it has a hybrid processor with a simplified instruction set, it is called a hybrid processor. processor. Has the following advantages:

(1) Strong processing capability (2) Fast computing speed, MSP430 series single-chip microcomputer can realize the instruction cycle of 40nS under the drive of 25MHZ crystal. 16-bit data width and multi-functional hardware multiplier can realize some algorithms of digital signal processing (such as FFT, etc.). (3) Ultra-low power consumption, the power supply voltage of the single-chip microcomputer is 1.8V-3.6V voltage, so when it can run under the clock condition of 1MHZ, the minimum current of the chip will be about 165uA, and the minimum current of the chip in RAM hold mode The power consumption is only 0.1uA. (4) Rich on-chip resources, 256K flash memory, 16K RAM, 12-bit ADC, 4 USCIs, 32-bit HW multiplier.

Fig. 5 is an infrared communication unit, and the infrared communication unit includes three parts, (1) is an infrared receiving unit, (2) is an infrared sending unit, and (3) is an infrared wake-up unit.

In order to realize the needs of functions such as hand-held adjustment, the system introduces infrared communication. At the same time, infrared communication is easily restricted and interfered by environmental conditions, and the use of high-power infrared emission tubes or receivers with optical filters can greatly improve the anti-interference ability of communication. The design of this device uses the high-efficiency IR7393C as the transmitting tube, and the integrated infrared receiver IRM3638L as the receiving tube. Among them, the optical power of IR7393C reaches 150mW, which can effectively enhance the anti-interference ability of infrared communication; The role of the detection output.

Working principle: the initial state/CVIR is high level, when there is an external infrared signal irradiated, the photosensitive diode V8 receives the light signal and turns on, the base of V10 is high level, V10 turns on, IR-R becomes low level, At this time, the CPU controls the /CVIR pin to be at a low level, turn on the VI pin, and VIR is at a high level. The optical signal is received and sent out after modulation and demodulation. The IR-T pin is controlled by the CPU to generate 38KHZ PWM.

Figure 6 LCD circuit, the LCD is an independent module, which is connected to the motherboard by plug-in, the LCD driver chip is BU97950, which supports 35*8=280 segment display driver, 2-wire serial interface SCA, SDA, built-in LCD drive power supply circuit.

Fig. 7 storage unit, storage unit comprises (one) serial E2PROM (two) FLASH memorizer. Serial E2PROM, as a metering device, has a lot of data such as voltage and current coefficients that change or can be modified by normal means, but cannot be rewritten due to interference in the system, let alone lost due to events such as power outages, so the device must meet the data requirements. The storage, and the serial E2PROM is suitable for this device. This device uses a serial EEPROM with a storage capacity of 256Kbit. It communicates with the MCU using the I2C interface. The circuit is shown in Figure 7. A0A1A2 is the address input pin. When multiple AT24LC256s are used at the same time, the corresponding high and low levels can be used as chip selection. The seventh pin WP is the protection pin, and SCL is the read/write clock control terminal. , SDA is the data output/entry for reading and writing.

FLASH memory, Flash memory is a memory that can be electrically erased and written in the system, and the information will not be lost after power failure. It has the characteristics of low power consumption, large capacity, and fast erasing and writing speed. This device uses AT45DB161D Flash memory, with Page, 512 bytes per page, with a total capacity of 16Mbit, internally integrates two data cache SPRAMs, and provides an SPI interface externally.

Figure 8 power supply circuit

The test device does not need external power supply when testing, and it is powered by a battery. The battery uses CR-P2 batteries from Wuhan Liyuan. Fast, small output ripple, low noise generated by work, etc. The output voltage of the chip is 5V. The test device has been considered in the design of low power consumption. The capacity of the battery is 1500mAh. The battery is turned on during the withstand voltage test, and the battery is turned off after the experiment is over. , the battery power consumption is about 8mA, and about 10,000 withstand voltage tests can be done.

Figure 9 clock circuit, the real-time clock uses the RX8025-T chip of EPSON Company, and its characteristics are as follows:

(1) Built-in high-precision 32.768KHZ DTCX (Digital Temperature Compensated Crystal Oscillator) (2) High-speed mode (400K) supporting I2C bus function (3) Timing alarm function (4) Fixed-period timing interrupt function (5) Time update Interrupt function (6) 32.768KHZ frequency output (with time energy 0E function) (7) Leap year automatic adjustment function (8) Wide range interface voltage: 2.2V to 5.5V (9) Wide range of time holding voltage 1.8V to 5.5V (10) Low current consumption: 0.8uA/3V.

Claims (9)

1. The AC withstand voltage test device samples the voltage from the withstand voltage instrument through the voltage sampling circuit, and the sampled voltage is sent to the metering device, and the metering device sends the data to the hybrid processor, and the hybrid processor stores the data in the Displayed on the display unit; the voltage sampling circuit adopts the principle of resistance voltage division, and multiple resistors are connected in series, and the last two resistors are connected in parallel with the corresponding capacitors and then grounded; The voltage sampling circuit is connected to the V2N/V2P voltage channel of the metering device, and the high-voltage signal from the withstand voltage instrument is converted into an AC signal with an amplitude of 0-1V through the voltage sampling circuit by using the complete differential input mode of the metering device. It is sent to the metering device through the voltage channel. 2. The AC withstand voltage testing device as claimed in claim 1, characterized in that, when the test device is powered on or the measuring device is disturbed and reset, the calibration data is updated by the hybrid processor through the SPI port; the SIG signal is used To notify the hybrid processor of a handshake signal, so the hybrid processor monitors the SIG signal. In order to enable the metering device to perform SPI operations synchronously with the hybrid processor after power-on and reset, the reset process keeps the RESET signal greater than 20us low power Ping, the chip is reset, at this time SIG outputs a high level, and then the hybrid processor pulls the RESET signal high, after a set time, the metering device is initialized, SIG outputs a low level signal, and then SPI operation is performed. 3. The AC withstand voltage testing device according to claim 1 or 2, characterized in that, both the RESET port of the metering device and the SIG input port of the hybrid processor are connected to decoupling capacitors. 4. The AC withstand voltage test device according to claim 1, wherein the hybrid processor is also connected to an infrared communication unit, a display unit, a storage unit, a clock circuit, a keyboard and a battery. 5. The AC withstand voltage testing device according to claim 1, wherein the metering device communicates with the hybrid processor through an SPI interface. 6. The AC withstand voltage test device according to claim 4, wherein the storage unit includes a storage chip AT24LC256 and a Flash memory AT45DB161D for storing data. 7. The AC withstand voltage testing device according to claim 4, wherein the infrared communication unit comprises an infrared receiving unit, an infrared sending unit and an infrared wake-up unit. 8. The AC voltage withstand test device as claimed in claim 7, wherein the initial state of the infrared communication unit /CVIR is at a high level, and when an external infrared signal is irradiated, the photodiode V8 is turned on when receiving the light signal, The base of the transistor V10 is at a high level, the transistor V10 is turned on, and the IR-R becomes a low level. At this time, the mixed processor controls the /CVIR pin to be at a low level, and the receiving tube VI pin is turned on, and the VIR becomes a high level. Level, receive optical signal, send out after modulation and demodulation, IR-T pin is controlled by hybrid processor to generate PWM. 9. The AC withstand voltage testing device according to claim 1, characterized in that, the outside of the testing device further includes an insulating shell.