Multimeter measured the forward resistance value of 0 reverse resistance value: What is the situation?
A mechanical meter, generally referred to as a pointer meter, shunts current through a resistor to bring the current flowing through the pointer head up to the rated value of the head, which happens to be full scale.
High-voltage diode can be more than one sub-high voltage diode in series, can also be sealed in series in a package.GTR (triode) type, if a single diode, will be made of very high voltage materials and processes, the general multimeter can not be measured.
Pointer meter Rx10k file more than one 10F20 15v battery, used to measure more than 100k resistance.
Multiple high-voltage diodes in series, if a single tube 1000v, withstand voltage 20000v need 20 in series, each tube voltage drop 0.7v, 20 is 14v, so most of the meter can only energy out of the diode within 10000v, higher withstand voltage need to meter itself also have a higher voltage to work.
If the forward measurement is zero, indicating that the breakdown, the normal value is 10,000v for 7k.(should be compared to zero first, otherwise the meter may burst)
Reverse measurement of 17.2K, accounting for one-third of the dial, the normal should be infinity, damage should also be zero resistance, not seen in kind can only speculate, the tube has been broken down, there are a large number of charcoal powder appears, the reverse when the amount of the diode is part of the half breakdown of the value of the diode is not broken down, the diode with the instrument tapped, the value should be fluctuating. In 10K gear, a diode is not broken or half-broken, the value itself is 700Ω, the measurement instrument display itself will be zero in the end.
Another possibility, the tube is normal, voltage resistance is not high, so the forward approximation of zero, reverse measurement of the hand do not touch the device, otherwise it will be measured out of the body resistance. There is no diode, direct measurement of the hand is also this value.
There is another possibility is less likely, but exists, germanium material diode will appear this phenomenon, this tube reverse leakage is larger, forward conduction 10,000 volts is less than 3K, reverse has a resistance value, but more random, can be large or small, but the tube is good.
