working principle  

It is divided into two parts: the main loop and the auxiliary loop. The main loop is adjusted by a large knob, and the auxiliary loop is adjusted by a small knob. The main circuit is used to control various output quantities through the "A/V selection" key switch on the instrument panel, and each time one output is switched, the "voltage/current meter" on the instrument panel can automatically monitor its output value. The auxiliary circuit directly adjusts the output through the output switch control, and the output value of the auxiliary circuit can be monitored by an external multimeter.

1. Principle of main circuit

The input AC220V power supply (through the internal insurance) enters the dual carbon brush voltage regulator T1 input terminal through the control relay K1, and then the power adjusted by the T1 large knob enters the isolation transformer T2 (JZ current booster), the booster has three taps Output, one tap is AC0～250V output, rated current is 3A; the output voltage of this tap can output 0～350V DC voltage after rectification and filtering; the second one is 20V (10A), this tap is output through the sensor through the relay control. 0～10A AC current, one way outputs 0～500mA AC current through resistance, one way through relay conversion can output 0～10A or 0～500mA DC current; the second tap is 15V (100A) high current terminal, this tap passes through the sensor Directly output 100A current at a time, this circuit has strong load capacity. However, the output is slightly overloaded and cannot be in a high current state for a long time.

2. Principle of auxiliary circuit

Like the main circuit, the input AC220V power supply (through internal insurance) enters the voltage adjusted by the small knob of the double carbon brush voltage regulator T1, and the isolation transformer T4 can directly adjust the output 0-20V or 0-250V AC voltage or 0-350V DC voltage, the rated current of this loop is 1A. Press the "auxiliary circuit switch" button switch and adjust the small knob to output.

3. Measuring circuit

The output of the main circuit adjusted by the large knob is AC "0～250V", "0～500mA", "0～10A", "0～100A". DC "0～350V", "0～500mA", and "0～10A" are converted by relays on the circuit board in the device. Each time a gear is switched, the corresponding output can also be monitored. Among them, the "0～500mA" gear includes when it is used in the "0～10A" gear, two clicks of "0～10A" is the "0～500mA" monitoring.

4. Time measurement

The instrument has a built-in 6-digit display stopwatch. The electric stopwatch can be started internally or externally. When starting internally, turn on the "main circuit switch" button switch on the instrument panel to start the stopwatch, and stop the stopwatch by shorting the stop watch terminal on the device panel through the contact. The stopwatch has a separate power switch, and the "stopwatch power" switch can be turned off when not in use.

5. Sound and light prompt

The instrument has a built-in acousto-optic prompt circuit. When the tested relay contact is activated, the contact can be connected to the acousto-optic prompt jack on the instrument panel, and the inside of the instrument emits an alarm sound or the light-emitting tube lights up to indicate the action of the breaker contact.