Multimeter measured forward resistance of 0 reverse resistance is what is happening
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 rating 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, 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 of 1000v, withstand voltage 20,000v need 20 in series, each tube voltage drop 0.7v, 20 is 14v, so most of the table can only energy out of 10,000v within the diode, higher withstand voltage needs to be the instrument itself also has 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 it may burst the meter)
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 lot of charcoal powder appears, the reverse is part of the measured half-broken down unbroken diode value, with the instrument tapped the diode, the value should be fluctuating. In 10K gear, a diode is not broken or half-broken, the value itself is 700Ω, measuring instrument display itself will be in the end to zero.
Another possibility, the tube is normal, voltage withstand 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.
