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| New UNI-T UT892 2000V AC/DC High Voltage Multimeter |
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| NoMoreMagicSmoke:
--- Quote from: Mechatrommer on September 11, 2022, 06:43:10 pm --- the reason you think its useless being there is because you havent seen its failing in such a manner yet. i dont think UNI-T is fool enough to put $1-5 part just as pure show off. you may argue that it is slow acting in ms range, but few ms second cutoff is better than few seconds of mass slaughter. --- End quote --- The reason I think it is useless is based on previous Uni-T meters. A quick peruse of Joe's video's will show multiple Uni-T meters with PTC's in them that breakdown at surprisingly low voltages. |
| joeqsmith:
Typically the low end meters I have looked at use a 5mm body. The small PTCs still have a lot of thermal mass (compared with how fast things would change with an arc). I would imagine if they did have a spark gap after the PTC, if it did come into play you may fine the PTC is missing it's coating after. |
| Fungus:
--- Quote from: NoMoreMagicSmoke on September 11, 2022, 06:26:49 pm ---PTC will only come into play with enough current to heat them up. --- End quote --- Which will be "never" when it's in series with 20MOhm, hence my curiosity. :-// But without a surge-rated resistor it's going to undergo a rapid uncontrolled disassembly in the case of an arc. Let's hope they go open-circuit when they fail. --- Quote from: Mechatrommer on September 11, 2022, 06:43:10 pm ---i dont think UNI-T is fool enough to put $1-5 part just as pure show off. --- End quote --- The only thing I can think of is they're using them as fuses. |
| NoMoreMagicSmoke:
--- Quote from: Fungus on September 11, 2022, 10:03:18 pm --- --- Quote from: NoMoreMagicSmoke on September 11, 2022, 06:26:49 pm ---PTC will only come into play with enough current to heat them up. --- End quote --- Which will be "never" when it's in series with 20MOhm, hence my curiosity. :-// But without a surge-rated resistor it's going to undergo a rapid uncontrolled disassembly in the case of an arc. Let's hope they go open-circuit when they fail. --- Quote from: Mechatrommer on September 11, 2022, 06:43:10 pm ---i dont think UNI-T is fool enough to put $1-5 part just as pure show off. --- End quote --- The only thing I can think of is they're using them as fuses. --- End quote --- Honestly a lot of Uni-T designs scream what a junior engineer would do if shown a bunch of meters that are "good" and told to make a new meter. You will get a meter that mostly looks good, but will be full of not quites due to the engineer not understanding the why behind the design choices. |
| Mechatrommer:
--- Quote from: Fungus on September 11, 2022, 10:03:18 pm ---The only thing I can think of is they're using them as fuses. --- End quote --- what do you think it is? Its designed to go open, surge Resistor will go short. It will need something else to go open anyway. which one you want to put in your design?, i can understand the suggestion of more robust input such as surge+fuse etc on a budget device, even though they missed the point of the economy. What i dont understand is removing a better perfectly working protection component in exchange with component that provides no protection at all. |
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