The Effectiveness of Digital Multimeter in Automatic Safety Test System for Leakage Current Detection

The Automatic Safety Test System is very powerful in terms of function, and there are many items that can be tested. It can be used for dielectric strength tests, leakage current tests and grounding resistance tests.

LISUN LS9955/LS9956 Automatic Safety Test System (electrical safety analyzer) combined the following function in one set: Withstand Voltage Test (AC/DC), Insulation Resistance Test (IR), Leakage Current Test (LLC), Grounding Resistance Test (GR) and Power Test.

Automatic Safety Test System LS9955 

I. Test Items of Automatic Safety Test System
1. Dielectric strength test: a few thousand volts of high voltage (AC or DC) is applied between the shell or the human-contact parts of the tested electrical appliance and the power line terminal, and the leakage current under this high voltage is detected, which may cause harm to the human body when the leakage current exceeds a certain value.
2. Leakage current test: divided into dynamic leakage and static leakage.
(1) Static leakage: the rated working voltage is 1.06 times the voltage applied between the shell of the tested electrical appliance and the power line, zero line terminals, and the maximum leakage current is detected when the tested electrical appliance is not working. The 1.06 times voltage applied should be provided by an insulated transformer.
(2) Dynamic leakage: while the tested electrical appliance is powered and running, the same test is performed as for static leakage (also known as hot leakage).
(3) When selecting a leakage current tester, the input impedance of the leakage current and the capacity of the isolation transformer should be focused. The input impedance of the test instrument should simulate the impedance network of the human body and different electrical appliance products have different models of human body network. The corresponding national standards have GB9706, GB3883, GB12113, GB8898, GB4943, GB4906, GB4706. The capacity of the output isolation transformer of the leakage current tester should be suitable for the capacity of the tested capacitor. When the tested electrical appliance is a motor, etc., the starting current is several times larger than the rated current, and the starting current should be taken into consideration.
3. Insulation resistance test: a DC voltage (usually 1000V, 500V or 250V) is applied between the shell or the human-contact parts of the tested electrical appliance and the power line terminal, and the leakage current under this voltage is tested and converted into insulation resistance.
4. Grounding resistance test: a constant large current (usually 10A or 25A) is applied between the shell of the tested electrical appliance and the grounding terminal, and the conduction resistance under this current is tested. Resistance is too large to play the role of grounding protection.

II. Calibration Methods of Automatic Safety Test System
The output high voltage of safety integrated testers has AC voltage and DC voltage, up to more than 5000V. The AC voltage is generally power frequency 50Hz or 60Hz, and the calibration includes the accuracy of AC voltage output and the distortion of voltage waveform.

The calibration of DC voltage includes the accuracy of DC voltage output and the size of voltage ripple. The high voltage output by safety integrated testers is connected to the voltage input end or the distortion meter input end of the digital multimeter through 1000:1 standard high voltage divider. If it is AC voltage, the value multiplied by 1000 is compared with the indication value of the safety instrument by using the AC voltage test function of the digital multimeter; the distortion is measured by the distortion meter, and the distortion should not exceed the specified value. If it is DC voltage, the value multiplied by 1000 is compared with the indication value of the safety instrument by using the DC voltage test function of the digital multimeter; and then the value multiplied by 1000 is the ripple, which should not exceed the specified value.

III. Features of Automatic Safety Test System

This series of testing instruments adopts backlight LCD screen, with soft light, high clarity and less affected by the surrounding light. The menu prompt and cursor indication are simple and clear. All screen display test results, multiple test conditions memory, can facilitate the test of various types of electrical appliances. With the microcontroller as its core, the test channel can capture the change of various parameters of the tested device in real time, and complete a test accurately in several seconds. With SPWM technology to generate 50 Hz or 60 Hz standard sine wave, and driven by high power MOS tube, output voltage and current can be adjusted without contact, greatly improving the reliability of instruments. In addition, the whole machine circuit adopts a variety of anti-interference measures, and has hardware and software protection to ensure safe and reliable operation. The instrument also has the features of automatic over-voltage/over-current protection and intelligent judgment of product test failure, with sound and light alarm.

Lisun Instruments Limited was found by LISUN GROUP in 2003. LISUN quality system has been strictly certified by ISO9001:2015. As a CIE Membership, LISUN products are designed based on CIE, IEC and other international or national standards. All products passed CE certificate and authenticated by the third party lab.

Our main products are Goniophotometer, Integrating Sphere, Spectroradiometer, Surge Generator, ESD Simulator Guns, EMI Receiver, EMC Test Equipment, Electrical Safety Tester, Environmental Chamber, Temperature Chamber, Climate Chamber, Thermal Chamber, Salt Spray Test, Dust Test Chamber, Waterproof Test, RoHS Test (EDXRF), Glow Wire Test and Needle Flame Test.

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