Electrogram pen working principle and precautions for use - Solutions - Huaqiang

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Kaixin micro test

Test probe P100-M3

The basic working principle of a standard low-voltage voltage tester is straightforward. When testing a live conductor, the metal tip of the tester touches the charged object, and the user holds the back end of the device with their hand. This creates a current path that flows through the tester’s internal components, including the neon bulb, resistor, human body, and eventually to the ground. This circuit completes, causing the bulb to light up if there is sufficient voltage present.
Typically, the tester will glow when there is a potential difference of at least 60 volts or more. If the bulb does not light, it indicates that the object being tested is not charged. In an AC system, both ends of the bulb will illuminate, while in a DC system, only one side will glow.
When using a voltage tester, it's important to follow certain safety precautions. First, differentiate between leakage current and static electricity. Some equipment may have ungrounded metal cases, which can cause the tester to light even though there is no real risk of electric shock. Electricians can use tools like multimeters or megohmmeters to distinguish between the two. Additionally, you can use the voltage tester itself: if the bulb flashes briefly and then goes out, it’s likely static; if it stays lit for a longer time, it indicates a leakage current.
Second, ensure proper handling of the tester. During testing, hold the pen with your thumb and middle finger, keeping the small window facing toward you. Place your ring and little fingers on the palm, and touch the device under test with the tip. If the bulb lights up, the device is energized. The brighter the bulb, the higher the voltage. If it doesn’t light, the device is not charged.
Third, always use the tester within its rated voltage range. Standard low-voltage testers are designed for voltages between 60 and 500 volts. Testing below 60 volts might lead to false readings, and testing above 500 volts can be dangerous and potentially cause electric shocks. Therefore, it’s crucial to only use the tester within its specified voltage limits.
Fourth, take necessary safety measures during electrical inspections. Always ensure that you are properly insulated to prevent electric shocks. For screwdriver-type testers, cover the longer part of the pen with an insulating sleeve, leaving only a small metal tip (about 10 mm) exposed for testing. This helps avoid phase-to-phase or phase-to-ground short circuits, especially in low-voltage environments where the distance between live parts is minimal. When checking closely spaced terminals, be extra cautious to avoid accidental contact that could result in a short circuit and injury. To further enhance safety, professional electricians are advised to wear insulated footwear and stand on an insulated platform or board. These steps significantly reduce the risk of electric shock and make the testing process safer and more reliable.