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Logic Probe

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4 years 9 months ago #30494 by Tutti57
Logic Probe was created by Tutti57
Does anyone use a logic probe? Is it a test light replacement? What situations would you use it in over a test light?

My Mac dealer screwed up so I got one for free.

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4 years 9 months ago #30498 by Tyler
Replied by Tyler on topic Logic Probe
The automotive logic probes I've seen connect to both power and ground, and end up working like an LED test light. The only advantage I've seen is not having to switch your polarity.

I haven't seen any value in owning one. But hey, maybe you'll end up loving it! :cheer:
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4 years 9 months ago #30499 by Tutti57
Replied by Tutti57 on topic Re:Logic Probe
ok, that's what I thought. I was messing around with it a little today and that's basically what I was thinking about it, the polarity thing. Might have to use some long jumpers to reach outside of the engine bay.

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4 years 9 months ago #30501 by Tutti57
Replied by Tutti57 on topic Re:Logic Probe
I've only have used an incondescent test light. What are the pros and cons of using an led?

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4 years 9 months ago - 4 years 9 months ago #30538 by Tyler
Replied by Tyler on topic Re:Logic Probe
Pros, you can't cook anything. :silly: Its current draw is almost non-existent, so you absolutely cannot harm an output.

Cons, it'll lie to you. :angry: The same low current draw can find a ground almost anywhere, which means it can show you screwy readings. Plus, it doesn't load the circuit in question the same way an incandescent bulb will, leaving questions about voltage drop.
Last edit: 4 years 9 months ago by Tyler.
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4 years 9 months ago #30568 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic Logic Probe
I have one of those LED test lights that tell you the polarity of what you are probing
I have never found a use for it.
When I want to use an LED test light I use one of those little LED votage probes sold as battery and altrnator testers. It cost about £4 / 5$ from my local Lidl Dicount Store

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



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4 years 5 months ago #34533 by FrugalPrepper
Replied by FrugalPrepper on topic Logic Probe
They have there use when you want to see the status of a circuit without changing it. For instance I want to see if the computer is pulling a control to ground. With a test light I cannot see it without potentially changing the circuit I am trying to test. A logic probe lets you see it without changing it.

A LED test light can sort of do this too, because of it's low current draw, but it can only show you when voltage is present, it has no light for ground. A basic logic probe like the HF one for instance will show up to 6, 12, 24 volts. So it is handy also to inspect a bus for data real quick without pulling down the signal. Just to see if your getting some kind of activity on the bus or not before breaking out a scope.
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