Relay protection tester consists of a main circuit and auxiliary circuit two circuit, the main circuit uses big knob adjustment, auxiliary loop using a small knob adjustment, the main loop through the panel on "output" pushbutton switch, various control its output, relay protection tester and each switching an output at the same time, the digital voltage / instrument. Current meter can automatically monitor the output value. The auxiliary circuit through the output switch control directly regulating the output, measurement can be attached to a multimeter. 
The main circuit principle of relay protection testing instrument:
AC220V power input by the insurance through the output control relay K1 into double brush voltage regulator T1 input, regulated by the T1 knob electricity into the isolation transformer T2 (part-time up-flow), up-flow three tap output, a tap for AC0-250V output, rated current is 3A; the tap output voltage after rectifying filtering can output 0-350V DC voltage; second pumping for 15V (10A), the tap through a sensor through the relay control output 0-10A alternating current through a resistor, the output 0-500mA alternating current, through a relay switching output 0-10A or 0-500mA DC current; second taps for 10V (100A) and large current terminal the tap through the sensor, a side directly to the output 100A current, the circuit with high load capacity, check meter relay protection but output slightly overload, not for a long time in the current state. Thermal relay calibrator
The auxiliary circuit of relay protection testing instrument:
Test equipment of relay protection secondary circuit and the main circuit, AC220V power through the voltage regulator double insurance into carbon T1 small knob adjustment, thermal relay tester through an isolation transformer T4 can directly regulate the output 0-20V or 0-250V AC voltage or DC voltage of 0-350V, the circuit of rated current is 1A. Press the auxiliary circuit "output control" switch, regulating knob can output.
The measuring circuit
By adjusting the knob of the main circuit of AC output "0-250V", "0-500mA", "0-10A", "0-100A", "0-350V" DC, "0-500mA", "0-10A" through the equipment circuit board relay switching, each switch a file, so can output the corresponding monitoring. The "0-500mA" file included in the "0-10A" file. When in use, in the "0-10A" two "0-500mA" is the monitor.
Time measurement
Device with built-in 6 digit display stopwatch, electric stop-watch internal start-up, but also external start. Internal starts, press the "output control" switch, you can start the stopwatch, through contact short joint equipment panel terminal can stop the stopwatch stopwatch. Stopwatch alone with the power switch, when not in use can be a stopwatch off.
Acousto-optic prompt
Circuit device with built-in acousto-optic prompting circuit breaker contacts, on the actions, thermal relay tester can contact access test box acousto-optic prompting jack, test box alarm sound or light, tips off electrical contact action.