TH9120A programmable AC voltage tester

TH9120 series AC/DC withstand voltage insulation resistance testers are designed to provide high voltage withstand voltage testing and analysis for high voltage optocoupler and high voltage relays, high voltage switches, PV modules and other devices with high insulation tolerance.

In terms of voltage resistance test, the output power AC: 200VA (10kV/20mA), DC: 120VA (12kV/10mA), so it can be used for high voltage stator, motor and other equipment to do the voltage resistance test, but also can do the same test on the parts. For insulation resistance test, the display range is 0.1MΩ-50GΩ, and the test voltage is 50V-5000V, which can be set arbitrarily. In the open and short circuit detection test, it can be judged whether the tested parts are reliably connected or not before the high voltage test is carried out. In terms of display, all test modes, time, voltage, current, resistance value, test steps, etc. are shown on the display, and there is another list display mode, which shows multi-step settings and sequential test results.

The instrument is equipped with HANDLER (robot interface), RS-232, LAN, USB DEVICE, USB HOST; optional GPIB interface, whether it is connected to the host computer, PLC, automation systems are at ease. One-key screenshot, one-key record function is convenient to save the test results to the U disk can be customized host computer software, the operation is more flexible, recording is more convenient.

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Functional Features

A. Insulation collapse test

Conventional test withstand voltage, as shown in Figure A-1, just set the rise time and test voltage value, if the test time, the measured parts appear to breakdown phenomenon, it will be judged that the withstand voltage is bad, directly cut off the test voltage. Therefore, the conventional withstand voltage test can only judge whether the withstand voltage is qualified under the specified voltage.

However, there are some passive components or materials that need to be tested for their high-voltage withstand level and derive an accurate crash voltage value, so the conventional voltage withstand test methods can't help. Therefore, TH9120A/TH9120D has added a crash voltage detection function, as shown in Figure A-2, the crash voltage test function is based on the set creepage start voltage, cut-off voltage, voltage step and time interval, and gradually measure the measured parts, when the measured parts appear to have poor insulation of the voltage withstand phenomenon, the automatic saving of this time the voltage value that is the crash voltage.

If the voltage value climbs to the cutoff voltage and the DUT does not collapse, the cutoff voltage can be reset, etc., and further analyzed until the correct collapse voltage value is obtained. The crash voltage test mode allows the component under test to be analyzed to accurately determine the level of voltage resistance that is causing insulation failures, which allows researchers to improve the weaker parts of the component's insulation.

B. Voltage insulation testing and arc detection (ARC)

Poor voltage withstand refers to the occurrence of electrical flashover or insulation damage in the voltage withstand test. Nowadays, voltage withstand insulation test has become the standard equipment for all kinds of electrical equipment and insulation material safety test. However, just considering the insulation failure can not completely solve the product safety problems, another type of phenomenon, arc discharge ARC in the withstand voltage test is getting more and more attention, discharge and insulation capacity has a very high correlation between, so the ARC detection is the key to control the quality of the product.

Arc discharge occurs in the following two cases:

a) When the material is subjected to high voltage and the electric field strength is greater than the ionization energy of the gas, the gas on the surface of the material will undergo transient ionization phenomenon, which will result in the formation of flames on the surface of the material and the formation of temperature rise phenomenon on the material. Prolonged ignition and temperature rise may result in a qualitative change of the material, leading to insulation deterioration, a decrease in voltage tolerance, and ultimately insulation failure.

b) the detection of parts under test when the distance between the points is too small, in the parts under test at both ends of the higher voltage applied, the detection of the air at both ends of the space will be ionized, the formation of the phenomenon of ignition, that is, the phenomenon of pulling the arc. Arc phenomenon produces high-frequency transient discharge, in the test process produces a high-frequency current signal as shown in the figure, arc detection (ARC) function is to use high-frequency power measurement to detect the way to determine whether the material insulation performance is bad.

C. Open Short Circuit Detection Function (TH9120A only)

In the process of withstand voltage test due to poor contact between the test piece and test line, test line damage, etc., open circuit phenomenon will occur, resulting in defective products misjudged as good products; damaged test piece or test end spacing is too small resulting in short circuit test line phenomenon, using OCS function, the instrument can detect the test end of the open and short-circuit situation in advance, to reduce the damage to the fixtures and equipment to save the cost of the test.

Typical withstand test products are capacitive (CDUT) and may range from tens of pF to several μF under normal conditions. An open circuit can be equated to a small capacitance COPEN of less than 10pF in series, making the total capacity much lower than normal. The capacitance at short circuit is much greater than the normal capacity. Therefore, it is possible to utilize the upper and lower limit values to judge the change in capacitance and reduce the occurrence of poor contact problems on the production line.

D. Pin detection (contact check function)

For contact checking problems during production line testing, in addition to the OSC function, a pin detection function (Fig. D) has been added to ensure that the DUT is reliably connected to the test line, improving test reliability and efficiency.

E. Rear panel output function

High voltage can be output on the rear panel of the instrument (Figure E), automated testing or system integration wiring is more beautiful and convenient.