EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Simon on May 17, 2014, 05:41:22 pm
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Mu BTEC L3 course in electronic engineering came with a logic probe and pulse generator in one. except I can't see how you can switch between the to functions. It's a TENMA 72-500 and the manual just talks about the two functions separately as though they are are not in the same device.
Any idea's, is this thing garbage or am i missing something ?
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The probe is the pointy bit along with the green/red triangular LEDs. This is always a probe.
The pulse generator is the 3 metal studs at the other end. You clip the croc clip to one of those then apply the other end of the lead to the circuit under test. The pulse gen is always running (when the thing is turned on), and you can select between 0.5Hz and 400Hz pulse stream.
The two studs closest to the yellow LED give you a pulse (10us/100mA capable) or square wave (5mA) output. The LED just shows when it's happening - slow flash for 0.5Hz, apparently always on for 400Hz. The last stud is an external sync input, letting you trigger the pulser from something else.
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Right, thanks, bit lame if you ask me but there you go. these days I'd not bother with a logic probe, just use my cheap crappy hand held scope that is crap as a scope but will give a very good insight into a signal.
Now i know why the meter probe with large crocodile clip lead was with it. bit fiddly if you ask me.....
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yes, the probe is a bit useless these days, but the pulser is jolly useful in conjunction with, say, a HP current probe. Just a shame the business stuff comes out the arse instead of the point bit :)
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All it would have taken was a 3 position switch to select between probe / pulse / square wave............. but i suppose it means you can use it as a probe and generator at the same time if you want a hand full of wires. I'd have expected the course to teach me to make my own pulse / wave generator with a 555......
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The idea of the probe isn't to go looking at stuff like you would with a scope, but to see if the pulse the other end puts out gets through whatever gate(s) you're checking for correct operation. The pulser is able to override normal logic outputs without damage, so you can do in-circuit verification of operation even when the gate is being held in some state by static inputs.
As such, the probe end would always be in use, so although you could rig your own switch it wouldn't be too useful :)