Methods for Testing Fluorescent Lamps with a Multimeter
A common fluorescent tube (lamp strip) has four pins. How are its internal parts connected and what is its working principle? How to judge whether a fluorescent lamp is good or bad with a multimeter? Please refer to the following content.
Each end of a common fluorescent tube contains a small filament. The two pins at each end of a good lamp are connected and have a very small cold resistance.
Here is the working principle of fluorescent lamps. A small drop of mercury is injected into the tube after vacuum pumping during manufacturing, and the tube wall is coated with phosphor powder. When the lamp starts, the filaments at both ends heat up, mercury vaporizes, gas is ionized to form a conductive path, and a large amount of ultraviolet rays are released. The ultraviolet rays excite the phosphor powder to emit visible light. In addition, when the lamp ages, the filaments at both ends evaporate, causing the tube ends to turn black. Even if the tube still emits light, it cannot be used anymore, and such lamps are difficult to start.
If you only need to judge whether the tube itself is damaged, the operation is relatively simple. Let's see how to judge the overall condition of the fluorescent lamp.
Test point L with a test pencil. If the pencil does not light up, the live wire is not connected.
Test point A with a test pencil (ballast output to lamp pin). If the pencil does not light up, the ballast is damaged.
Test point B with a test pencil. If the pencil does not light up, filaments A and B are broken.
Short-circuit B and C (the two ends of the starter). If the lamp does not light, filaments D and C are broken; if the lamp lights, the starter is damaged.
Test point N with a test pencil. If the pencil does not light up, the neutral wire is broken.
