The withstand voltage tester consists of a voltage boosting section, a control section, and a display circuit. The voltage boosting section comprises a voltage regulating transformer, a step-up transformer, and a power on/off switch for the boosting section. Users can control the output voltage of the step-up transformer by adjusting the voltage regulator. The control section consists of a current sampling circuit, a timing circuit, and an alarm circuit. It is responsible for starting the test, monitoring the current to trigger an alarm and cut off the power when the current exceeds the set value, and cutting off the power after the timer ends or a reset signal is received. The display circuit displays the output voltage value of the step-up transformer, the current value of the current sampling section, and the countdown timer value of the timing circuit.
The core difference between a programmable withstand voltage tester and traditional instruments lies in the voltage boosting section. Its high-voltage boosting is not regulated by a voltage regulator using mains power, but rather by a single-chip microcomputer controlling the generation of a 50Hz or 60Hz sine wave signal, which is then amplified and boosted by a power amplifier circuit. The output voltage value is also controlled by the single-chip microcomputer. Modern withstand voltage testers can be integrated with industrial computers, barcode scanners, and other equipment to form an automated testing system, receiving control commands and returning test results via a communication module.
Taking the VT2008 ultra-high voltage withstand voltage tester as an example, its working principle block diagram shows that the relay controls the connection or disconnection of the high voltage output, the voltage regulator (mainly composed of a voltage adjuster) changes the voltage, the high voltage transformer increases the voltage, the current detector converts the current flowing through the test device into voltage and compares it with a reference voltage before outputting a detection signal to the controller. The controller controls the relay and alarm circuit based on signals from the current detector and the start, reset, and timing functions. The timer performs timed testing, and the alarm circuit drives the buzzer and over-leakage lamp to issue an audible and visual alarm and automatically disconnects the high voltage when the leakage current exceeds the set value.
Modern programmable withstand voltage testers have functions such as programmable test steps, flashover detection, and rapid discharge. They can also perform insulation resistance testing (IR) and withstand voltage testing (ACW/DCW) in one operation and are equipped with multiple communication interfaces (such as RS-232, GPIB).
