Explain the rapid measurement method of transformer DC resistance tester:
The device consists of 80C196 microcontroller as the core of the microcontroller control unit, through the data memory and I / O port expansion to complete the test and control functions. The overall structure of this test system is shown in Figure 5-1
The power supply part is through a switching power supply to generate the microcontroller power supply +5V and ±12V, where the relay power supply +12V is stepped down by the transformer, rectifier bridge rectification. There are only four buttons on the keyboard, and functions are selected through the buttons to complete the test, storage, and printing functions. The test result is output through the LCD display.
The microcontroller control unit is mainly composed of 80C196 single-chip microcomputer, external program memory EPROM27128, data memory RAM6264 and E2PROM2864. The decoding circuit is implemented by two 74LS138s. The address latch is completed by the 74LS373. The I/O port expansion is realized by a 8255, which realizes the control of the printer, the control of the output relay, the input of the keyboard, and the control of the liquid crystal display.
The constant current source circuit is mainly composed of a constant current source sampling circuit, a comparison circuit, etc., and the alternating current is converted into a direct current through a rectifier bridge, and after current adjustment and current feedback, a steady current output of 0.1A to 10A is finally achieved.
The measuring loop is mainly controlled by the constant current source output stable current directly through the power transformer windings, does not connect the standard resistor (short-circuit the series resistor relay), measuring the charging current, when the charging current reaches the set value, the relay will be disconnected. The resistors are serially connected to the measuring circuit. In order to ensure the stability of the microcontroller power supply, the relay control power supply alone.
Due to the presence of winding inductance, residual currents pose a threat to users and test equipment. Therefore, there must be a current discharge circuit. The current discharge circuit of the transformer DC resistance tester is composed of a discharge resistor and a reverse diode. The diode is turned off when charging. The winding is charged, the diode is turned on when the power is off, and the winding is discharged through the diode and discharge resistor.
5.1.2 Microcontroller Control Unit Circuit The 80C196 microcontroller is particularly suitable for various types of automatic control systems, such as industrial process control systems, servo systems, distributed control systems, variable frequency speed control motor control systems, etc., as well as general signal processing systems and advanced Intelligent instruments, and high-performance computer external device controllers and office automation device controllers, compared with the MCS-51 series, the 80C196 microcontroller has improved performance in the following aspects: The arithmetic logic unit in the CPU does not use the conventional accumulator Structure, using a register-register structure The operation of the CPU directly addresses 256-byte registers. Eliminates the bottleneck effect of the accumulators present in the general CPU architecture, improving the operating speed and data throughput.
The 24 bytes in the 256-byte register are special registers. The remaining 232 bytes are general-purpose registers, and the number of general-purpose registers is much larger than that of general-purpose CPUs. This makes it possible to designate special registers for local variables in each interrupt service routine, eliminating the software overhead that is paid by the protection register field and restoring the register field during the interrupt service, and greatly facilitating the program design.
There is a more efficient, faster execution command system. Transformer DC resistance tester can operate on signed and unsigned numbers; 16-bit by 16-bit instruction execution time is 14 state cycles; 32-bit divide-by-16 instruction execution time is 26 state cycles; and symbols Expansion, data normalization (used in floating point calculations) and other instructions. In addition, three-operand instructions greatly increase instruction efficiency.
In addition to the above points, the 80C196 microcontroller also integrates a richer set of peripheral devices, such as clock generator, timer/counter, standard input/output port, full-duplex asynchronous serial input/output port, and watchdog timer (Watchdog ), to improve the system's anti-jamming capability, analog / digital converters, high-speed input / output devices, pulse width modulation output.
Transformer DC resistance tester technical parameters:
1, the current profile: the output current is: automatic, 1A, 500mA, 100mA, 50mA, 10mA, 5mA, ≤ 5mA.
2. Resistance file: Select the resistance as: automatic, ≤4Ω, ≤8Ω, ≤40Ω, ≤400Ω, ≤2KΩ, ≤5KΩ, 200KΩ.
3, resolution: 0.1μΩ
4, range: 2KΩ-200KΩ (≤ 5mA file)
10Ω-5KΩ (5mA file)
1Ω-2KΩ (10mA file)
200mΩ-400Ω (50mA file)
100mΩ-200Ω (100mA file)
50mΩ-8Ω (500mA file)
10mΩ-4Ω (1A file)
5. Accuracy: 2‰±2 words 6, working temperature: 0 to 40 degrees 7, working humidity: <90%RH, no condensation
The device consists of 80C196 microcontroller as the core of the microcontroller control unit, through the data memory and I / O port expansion to complete the test and control functions. The overall structure of this test system is shown in Figure 5-1
The power supply part is through a switching power supply to generate the microcontroller power supply +5V and ±12V, where the relay power supply +12V is stepped down by the transformer, rectifier bridge rectification. There are only four buttons on the keyboard, and functions are selected through the buttons to complete the test, storage, and printing functions. The test result is output through the LCD display.
The microcontroller control unit is mainly composed of 80C196 single-chip microcomputer, external program memory EPROM27128, data memory RAM6264 and E2PROM2864. The decoding circuit is implemented by two 74LS138s. The address latch is completed by the 74LS373. The I/O port expansion is realized by a 8255, which realizes the control of the printer, the control of the output relay, the input of the keyboard, and the control of the liquid crystal display.
The constant current source circuit is mainly composed of a constant current source sampling circuit, a comparison circuit, etc., and the alternating current is converted into a direct current through a rectifier bridge, and after current adjustment and current feedback, a steady current output of 0.1A to 10A is finally achieved.
The measuring loop is mainly controlled by the constant current source output stable current directly through the power transformer windings, does not connect the standard resistor (short-circuit the series resistor relay), measuring the charging current, when the charging current reaches the set value, the relay will be disconnected. The resistors are serially connected to the measuring circuit. In order to ensure the stability of the microcontroller power supply, the relay control power supply alone.
Due to the presence of winding inductance, residual currents pose a threat to users and test equipment. Therefore, there must be a current discharge circuit. The current discharge circuit of the transformer DC resistance tester is composed of a discharge resistor and a reverse diode. The diode is turned off when charging. The winding is charged, the diode is turned on when the power is off, and the winding is discharged through the diode and discharge resistor.
5.1.2 Microcontroller Control Unit Circuit The 80C196 microcontroller is particularly suitable for various types of automatic control systems, such as industrial process control systems, servo systems, distributed control systems, variable frequency speed control motor control systems, etc., as well as general signal processing systems and advanced Intelligent instruments, and high-performance computer external device controllers and office automation device controllers, compared with the MCS-51 series, the 80C196 microcontroller has improved performance in the following aspects: The arithmetic logic unit in the CPU does not use the conventional accumulator Structure, using a register-register structure The operation of the CPU directly addresses 256-byte registers. Eliminates the bottleneck effect of the accumulators present in the general CPU architecture, improving the operating speed and data throughput.
The 24 bytes in the 256-byte register are special registers. The remaining 232 bytes are general-purpose registers, and the number of general-purpose registers is much larger than that of general-purpose CPUs. This makes it possible to designate special registers for local variables in each interrupt service routine, eliminating the software overhead that is paid by the protection register field and restoring the register field during the interrupt service, and greatly facilitating the program design.
There is a more efficient, faster execution command system. Transformer DC resistance tester can operate on signed and unsigned numbers; 16-bit by 16-bit instruction execution time is 14 state cycles; 32-bit divide-by-16 instruction execution time is 26 state cycles; and symbols Expansion, data normalization (used in floating point calculations) and other instructions. In addition, three-operand instructions greatly increase instruction efficiency.
In addition to the above points, the 80C196 microcontroller also integrates a richer set of peripheral devices, such as clock generator, timer/counter, standard input/output port, full-duplex asynchronous serial input/output port, and watchdog timer (Watchdog ), to improve the system's anti-jamming capability, analog / digital converters, high-speed input / output devices, pulse width modulation output.
Transformer DC resistance tester technical parameters:
1, the current profile: the output current is: automatic, 1A, 500mA, 100mA, 50mA, 10mA, 5mA, ≤ 5mA.
2. Resistance file: Select the resistance as: automatic, ≤4Ω, ≤8Ω, ≤40Ω, ≤400Ω, ≤2KΩ, ≤5KΩ, 200KΩ.
3, resolution: 0.1μΩ
4, range: 2KΩ-200KΩ (≤ 5mA file)
10Ω-5KΩ (5mA file)
1Ω-2KΩ (10mA file)
200mΩ-400Ω (50mA file)
100mΩ-200Ω (100mA file)
50mΩ-8Ω (500mA file)
10mΩ-4Ω (1A file)
5. Accuracy: 2‰±2 words 6, working temperature: 0 to 40 degrees 7, working humidity: <90%RH, no condensation
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