Logic Probes

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buaku

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Since I keep seeing threads where having a logic probe would be useful I figure it wouldn't hurt to get one.

What are some key features to look for in a logic probe?
I see some that have a max signal frequency of 20MHz or 50MHz and different input impedances of 1M Ohms or 120K Ohms. I'm guessing the smaller pulse width it can detect the better?

Any help would be appreciated!
 
mainman

mainman

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buaku said:
Since I keep seeing threads where having a logic probe would be useful I figure it wouldn't hurt to get one.

What are some key features to look for in a logic probe?
I see some that have a max signal frequency of 20MHz or 50MHz and different input impedances of 1M Ohms or 120K Ohms. I'm guessing the smaller pulse width it can detect the better?

Any help would be appreciated!
Click to expand...


Get what you can afford the 20 or the 50. If money is no issue get a scope man, probes aren't that helpful because they really give you minimum information.
 
Hewitson

Hewitson

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Yeah couldnt agree more. A logic probe is much better than nothing, although it doesnt do anything a multimeter can't. A 2 channel oscilloscope is a far more useful tool and can be bought relatively cheaply these days.
 
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buaku

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I always thought it'd be cool to have an o-scope.
Since I don't need a logic probe right away maybe I should turn my attention to an oscilloscope.

Thanks for the input!

How would you make a multi-meter mimic a logic probe? Does it need to have a logic probe type of setting?
 
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li_gangyi

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No, 5V = logic high, close to 0V = logic low. Anything in between = prossibly busted IC. It depends on how fast your multimeter is really...

If you're getting a logic probe, look for one that supports tri-state, High, Low and High Impedance (disconnected). This will let you know if the pin you are probing is disconnected, instead of showing a false high or low (or nothing).
 
channelmaniac

channelmaniac

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Wow...

I fix a lot of boards and use my logic probe 95% of the time. The scope sits unused most of the time.

If you want one, I have some I picked up locally that I'll sell after checking them out. They are the same as the one I use in the shop - Eico - that has the sound capabilities too.

RJ
 
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buaku

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channelmaniac said:
Wow...

I fix a lot of boards and use my logic probe 95% of the time. The scope sits unused most of the time.

If you want one, I have some I picked up locally that I'll sell after checking them out. They are the same as the one I use in the shop - Eico - that has the sound capabilities too.

RJ
Click to expand...

Sure, if you got some working spares to sell I'd be more than happy to buy one from ya!
 
Hewitson

Hewitson

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Do you mean they are also an audio probe, or they make sounds when they detect logic levels?
 
channelmaniac

channelmaniac

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They make different sounds at different logic levels.

But, the cool thing is that you CAN use them as a rudimentary audio probe. It sounds awful, but you can probe the outputs of the Yamaha DAC chips and hear the sounds coming from it.

It helps with troubleshooting sound circuits because you can use that to quickly narrow down problems to either the digital section or analog section with that test. The audio levels also help when probing the board because you don't have to look at the lights to know what is going on in the circuit.

RJ
 
channelmaniac

channelmaniac

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OOPS..

I screwed up... These are the 610 and not the 610B probes... URG...

They are probes without audio.

But, they are tested and up for sale. Buaku has first stab at it.
 
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