all my DMM's output more than 2.5V in the diode/continuity/resistance modes, I need something that will be under 0.1V.A standard multimeter with a continuity range - generally operating a buzzer to indicate continuity.
0.1 V for a continuity tester? An interesting idea.hi,
can someone recommend a simple circuit for a low voltage, low current continuity tester for in-circuit probing that will not turn on semiconductor junctions?
thanks!
looks interesting, I'll have to see if I have the parts to build it. There are however two comments posted there saying that the circuit does not work, hmm...
hi,
can someone recommend a simple circuit for a low voltage, low current continuity tester for in-circuit probing that will not turn on semiconductor junctions?
thanks!
One of my favorite methods! I replace an alleged probe tip with a 1/8th inch Allen wrench and sharpen that little bit of tool steel.Sharpened its probes to allow piercing solder
Nice use of a current mirror to keep the output voltage low. Then a Darlington to completely ruin the current limiting feature? Brilliant.Here is a version of an in-circuit tester I have used for years:
I think of the operation a little differently. Q1 is run at a current of somewhat less than 1 uA. The Sziklai pair (Q2 and Q3) is used to reduce the current through the base-emitter junction of Q2. This makes the diode drop of Q2 less than the diode drop of Q1. This difference is the voltage seen at the probes.Nice use of a current mirror to keep the output voltage low. Then a Darlington to completely ruin the current limiting feature? Brilliant.
I was puzzling about a 300pf load characteristic until I realized it is irrelevant to the primary function.
Hey, I design them backwards. Sometimes I read them backwards.
If we both thought in the same way, one of us wouldn't be necessary.I think of the operation a little differently.
Ah, but in this case we differ by a diode drop.You say Siklai, I say Darlington.
On the schematic there is a component U1, connected to the legs of C1 0.1uF, what is that?Here is the one I built and use almost daily. I played with the values of R3 and R4 to lower the detection of continuity to less than 25 Ω
http://nerdfever.com/improved-w4zcb-continuity-tester/
Graham
two ways to do it:I need something that will be under 0.1V.
by Duane Benson
by Jake Hertz
by Aaron Carman
by Jake Hertz