Thermal resistor failure
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This post was last edited by zyzs on 2012-3-27 at 19:56. I’m seeking advice from experts! Today, when I went to the site, I found a PT100 thermistor; after removing the wires, no resistance could be measured at either the AB or AC terminals. I tried all of the resistance measurement settings on the multimeter, but still no resistance was detected. The multimeter is not damaged. What could be the cause of this issue?
Can the resistance be measured on the BC side? It’s probably broken.
How is it possible that the resistance value cannot be measured? The resistance value should exist objectively. When it’s said that the resistance value cannot be measured, it’s either zero or infinite; zero indicates a short circuit, while infinity indicates an open circuit
The thermal resistor is probably broken. What’s its model? Armored types are difficult to repair; usually, they need to be replaced.
Is bc conductive? If there’s no resistance as you said, then it’s equivalent to a short circuit with ac; if the resistance is infinite, then there’s a break in the connection
When the resistance cannot be measured, does it display zero or infinity? If there is suspicion that the resistor is faulty, it can be taken out for inspection. In the case of thermal resistors used in field applications, those with ordinary tile-type enclosures may have broken silver leads or damaged connection points; for those with an armored structure, the problem is usually a broken lead at the connection terminals. Ordinary types are easy to repair, while in the case of armored types, if the break occurs at the seal area of the armor, it becomes quite difficult to fix.
If no resistance value can be measured, it means there’s a broken wire in the resistor; replace it. It doesn’t cost much anyway
As you mentioned, the PT100 might be damaged; in manufacturing, it’s quite common for thermal resistors to fail. It’s possible to replace just the core or the entire resistor, and it’s a cheap procedure that doesn’t cost much.
It is preliminarily determined that line A is broken. Measuring lines B and C shows resistance, and this resistance is close to 0, which indicates that line A is broken
Make it clear whether the reading is zero or infinity; in either case, the thermal resistor is damaged and needs to be replaced. Just replace the core, and then test it again
A broken wire should result in an out-of-range resistance reading; a short circuit shouldn’t be detectable