| Products > Test Equipment |
| Big Clive's "Trashy" meter, unboxed ( Duratool D03047 multimeter ) |
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| IanB:
Some meters have a multi-gigaohm input impedance, and while I don't know how this is implemented, I would guess the input more or less is going directly to the gate of an FET? If that is the case, is there any way these can have robust input protection? |
| David Aurora:
--- Quote from: IanB on April 27, 2023, 12:35:40 am --- --- Quote from: David Aurora on April 26, 2023, 11:56:43 pm --- --- Quote from: IanB on April 26, 2023, 04:13:52 pm ---I'm making an analogy. A sensitive mechanical instrument should be treated with mechanical care. Similarly, a sensitive electrical instrument should be treated with electrical care. --- End quote --- You're kind of making the same mistaken assumption as the OP here that everything is always controllable- it's not. Devices fail while under test, surges happen, test points can be mislabeled, probing mistakes happen, etc. --- End quote --- There's no mistaken assumption here. If you drop your expensive micrometer on the concrete floor and put it out of alignment, that's tough on you, time to buy a new one. Similarly, if you blow up your expensive bench meter by accident, that is similarly tough on you. Time to replace it or get it repaired. What you don't do is get the probes from that expensive meter and recklessly stick them in unknown circuits. If you do that you have only yourself to blame for mishaps. --- End quote --- If you're only ever sticking your probes in circuits you know back to front, that are well documented and are guaranteed to be behaving correctly I've got to assume you're unemployed. Jesus Christ. From one day to another all sorts of shit lands on my bench for inspection, often already worked on by cowboys or DIYers. Just the last few disasters that spring to mind are a power switch where a terminal had somehow internally shorted to the actuator, a tube amp where some numb nuts had wired the 450V B+ directly to the input jack, missing insulation between transistors and heatsinks, incorrectly connected transformers... the list goes on. Surprises happen and sometimes your probes find something you weren't expecting, welcome to the real world. --- Quote from: IanB on April 27, 2023, 02:34:25 am ---I have a small question for everyone in this thread: do your lightbulbs have a CAT rating on them? When you twist a bulb into its socket, do you ever worry about it exploding in your hand? Do you wear safety glasses and rubber shoes when you change a lightbulb? A DMM may be connected to the mains for a few seconds at a time to take a reading, and there is only one of them. All the lamps in your house are connected to the mains 24/7 and switched on for hours at a time. They could explode, cause a fire, or cause human injury. The risk is vastly higher than with using a DMM. Why are there many threads about meters, and no threads about household appliances and electrical devices? There are millions more of the latter, and a proportionately higher hazard, statistically. --- End quote --- I turn the switch off before changing them, because I'm not a fucking idiot. To each their own though I guess :-// |
| Grandchuck:
I am curious if there are any auto mechanics on this forum? EV battery voltage can be as high as 800V. And, the energy stored is significant. What does this group (auto mechanics) do about using instruments safely? |
| Fungus:
--- Quote from: David Aurora on April 27, 2023, 03:27:59 pm ---I turn the switch off before changing them, because I'm not a fucking idiot. To each their own though I guess :-// --- End quote --- What if it's a two (or three) way switch and you don't know if it's on or off? Do you rewire your house first? |
| wasedadoc:
--- Quote from: Fungus on April 27, 2023, 04:32:15 pm --- --- Quote from: David Aurora on April 27, 2023, 03:27:59 pm ---I turn the switch off before changing them, because I'm not a fucking idiot. To each their own though I guess :-// --- End quote --- What if it's a two (or three) way switch and you don't know if it's on or off? Do you rewire your house first? --- End quote --- The neon screwdriver would come out of that drawer in the kitchen that has the non-cooking items such as string, Stanley knife, spare keys, candles, fuse wire, tap washers etc. |
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