What happens if the forward resistance measured by a multimeter is 0 and there is resistance in the reverse direction?
Mechanical watches generally refer to pointer watches. The current flowing through the pointer meter head reaches the rated value of the meter head through resistor shunting. At this time, it is exactly the full scale.
The high-voltage diode can be composed of multiple sub-high-voltage diodes connected in series, or it can be connected in series and sealed in a package. GTR (transistor) type, if it is a single diode, it will be made of materials and processes with very high voltage resistance, and generally cannot be measured with a multimeter.
The Rx10k range of the pointer meter usually uses a 10F20 15v battery to measure resistance above 100k.
Multiple high-voltage diodes connected in series. If a single tube is 1000v and the withstand voltage is 20000v, 20 diodes need to be connected in series. The voltage drop of each tube is 0.7v. 20 diodes are 14v. Therefore, most meters can only measure diodes within 10000v. Higher voltage resistance requires a meter. It also needs a higher voltage itself.
If the forward measurement is zero, it indicates breakdown. The normal value is 10,000V which is 7k. (Should be reset to zero first, otherwise the meter may explode)
The reverse measurement is 17.2K, which occupies one-third of the dial. Normally it should be infinite, and the damage should be zero resistance. Without seeing the actual object, we can only speculate that the tube has broken down and a large amount of carbon powder has appeared. The measured value when reverse is If the diode value is partially broken down and not broken down, tap the diode with an instrument and the value should float. At the 10K level, if a diode has no breakdown or half breakdown, the value itself is 700Ω, and the measurement instrument display itself will be zero.
Another possibility is that the tube is normal and the withstand voltage is not high, so the forward direction is approximately zero. Do not touch the device when measuring in the reverse direction, otherwise the human body resistance will be measured. Without a diode, the same value can be measured directly by hand.
There is another possibility that is less likely, but exists. This phenomenon will occur with germanium material diodes. This kind of tube has a large reverse leakage. The forward conduction is less than 3K at 10,000 volts. There is resistance in the reverse direction, but it is random and can be large. It's small, but the pipe is good.
