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I finally stopped using cheap multimeters after a field repair gone wrong
Was working on a Cessna 172 last Tuesday and used my $15 Harbor Freight multimeter to check a voltage drop on a nav light circuit. The thing read 11.8 volts where it should have been 13.2. I swapped it out for a Fluke 117 a coworker loaned me and it showed the exact reading I expected. Turns out those cheap meters drift badly once they get a little age on them. Looked up the specs online and saw the accuracy tolerance is like 3% on cheap ones versus 0.1% on the better brands. That difference could mean signing off a bad relay as good. Has anyone else had a cheap meter lead them down the wrong path?
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charlies374d ago
Was that 3% spec at the time of manufacture or after it aged a bit? Those Harbor Freight meters seem to get worse the longer you own them.
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Not sure I buy this. 3% at 12 volts is 0.36 volts, not nothing but you can still see a 13.2v system running at 11.8v is way low regardless of the meter. @charlies37 is right that the spec goes out the window after a year of sitting in a toolbox. But the real problem is those cheap meters also have terrible input impedance. They load down the circuit you're testing and give you a false low reading. I've seen a $10 meter pull a signal down by over a volt on a high resistance circuit. So it's not just the drift, it's the whole design. A Fluke costs more because it doesn't change the circuit it's measuring. That's the part people miss.
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mason_reed474d ago
Call me crazy but 3% drift on a 12v reading is only like 0.3 volts, that's probably not what made your day go sideways lol.
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