Using a multimeter, how to assess the caliber of fluorescent lighting
The four pins of ordinary fluorescent tubes (light strips), how are they connected inside, what is their working principle, and how to use a multimeter to judge whether the fluorescent lamp is good or not, refer to the following.
Ordinary fluorescent tubes have a small filament at each end, and the two legs at each end of a good tube are connected when measured with a multimeter, with only a small cold-state resistance.
Let’s look at the working principle of the fluorescent lamp here. During manufacture, the lamp tube is filled with a small drop of mercury (mercury) after vacuuming, and the tube wall is coated with fluorescent powder. When the lamp tube is started, after the filaments at both ends are heated, the mercury Evaporated into gas, the gas is ionized and conducts electricity to form a circuit. At the same time, the gas emits a large amount of ultraviolet rays, and the ultraviolet rays excite the fluorescent powder to emit visible light. In addition, when the lamp tube ages, the filaments at both ends evaporate and cause the two ends of the lamp tube to turn black, and the lamp tube cannot be used even if the filament is not broken. This kind of lamp tube is difficult to start.
If you just judge whether the lamp is broken, it is relatively simple. Let's see how to judge the overall quality of the lamp.
1. Measure the L point with the electroscope pen. If the electroscope pen does not light up, the live wire is not connected.
2. Measure point A (from the ballast to the lamp pin) with an electroscope pen. If the electroscope pen does not light up, the ballast is broken.
3. Use the electroscope to measure point B. If the electroscope does not light up, the filaments of A and B are broken.
4. Short circuit B and C (both ends of the starter). If the filament is not on, the D and C filaments are broken; if it is on, the starter is broken.
5. Use an electroscope to measure point N. If the electroscope lights up, the zero line is broken.
How fluorescent lamps work
At the beginning of turning on the light, "A and B" are connected to "C and D" through the glow starter, and the filaments are energized in series to preheat. Then, the glow starter is disconnected due to energization and heat, which causes the magnetic ballast to generate high voltage, which breaks down the "Penning" gas in the lamp tube, and the lamp turns on. Finally, the magnetic ballast maintains a certain current between A and D, and the lamp emits light stably.
How to Repair Fluorescent Lamps
1. Use a multimeter to measure the fluorescent tube, and measure the two feet at one end. If it is open circuit, the fluorescent tube will not be able to glow, and it must be useless. (The two legs on the same end are the same filament)
2. Adjust to the ohm gear, and use the two probes of the multimeter to test the connection terminals of the ballast. The meter shows that as long as it is not connected directly, there is a certain resistance value. If the circuit is broken, it must be broken.
3. There is a neon bulb in the starter, and a bimetal in the neon bulb is in a disconnected state. After electrification, the neon gas glows and heats up, so that the bimetal is deformed by heat and connected. Therefore, it is generally open circuit, if the path is damaged.
Explanation: Even if the starter is not short-circuited with a multimeter, it does not mean that the starter is good. Conversely, if the starter is on as measured by a multimeter, then the starter must be bad.
