testing with a multimeter, no connection?

Started by The Rocket From The Tombs, August 07, 2012, 01:31:18 AM

Previous topic - Next topic

The Rocket From The Tombs

I made the board, ordered the components and soldered them up but, my multimeter doesn't show continuity for some components. I don't see where the components could have gone bad, they're all brand new, soldered them the same day they arrived. The Multimeter is also new, with a new battery. Are there any other factor that could give the meter false readings? I'm hoping I won't need to replace any. Also, to clarify I don't mean the solder joints I'm testing the actual leads.

Jdansti

You are trying to measure continuity across the leads of the resistors, capacitors, transistors, etc?  If so, this is not a normal thing to do.:)  Think about it-if your meter was set to continuity and beeped when you measured across all of your components' leads, they would all be acting like pieces of wire!  As an example, diodes allow current to only flow in one direction. Put your probes on a diode and then switch them to the opposite leads.  You'll get a continuity beep in one direction and nothing in the other. The continuity function might work on low value resistors, but put your probes on a 1M and you'll get nothing.

There are specific methods of checking each type of component. Another thing to note is that depending on the circuit, you could get false readings when the components are soldered to the PCB, even if you use the correct method of measurement. 

You didn't mention why you were trying to check the components. I assume that the circuit was not working as intended. 99% of the time when a board doesn't work, it's not because of faulty components, but operator error. :-\ It happens to ALL of us - every single person on this forum!  Trouble shooting our errors is a major part of pedal building.

Go to http://www.diystompboxes.com/smfforum/index.php?topic=29816.0 and follow the instructions. This will help the forum members help you. Thanks!





  • SUPPORTER
R.G. Keene: EXPECT there to be errors, and defeat them...

The Rocket From The Tombs

Haha, first of all thanks for taking the time with such a nooby question. Actually, after I finished soldering everything I wanted to test if the circuit would work before I finished it, since it has a bunch of external wiring. I had read a brief guide on multimeters that said continuity would tell me if something was making connection. Then, since the readings were flaky, I started to doubt whether the circuit would work. Anyway, thanks for clarifying that for me, it should work fine then.

Jdansti

  • SUPPORTER
R.G. Keene: EXPECT there to be errors, and defeat them...

PRR

"Continuity checks" are for trailer lights.

Everything "has continuity" to everything else. Measure across a long clean dry glass rod. It has maybe 1,000,000,000,000 ohms. That's continuity, but not much.

Continuity checkers must have a built-in assumption. Something like "beep only if under 100 ohms"(*).

That's great for checking trailer lights. A good wire is under 1 ohm. A perfectly broken wire might be millions of ohms. A cruddy tarnished contact might be 10,000 ohms, which "is continuity", but not enough to power a trailer light, so it might as well be perfectly bad.

Also fine for jack to board to first cap. Even your longest thinnest wire or board-trace is under 1 ohm, should beep a common continuity checker. And if one end of C1 is supposed to connect to one end of R1, a beeper probe on those ends of C1 and R1 should beep.

End-to-end on a 120 ohm or 1K ohm resistor would not beep.

A beep test _across_ C1 probably should not beep (caps don't pass steady DC current) or make a very short peep (caps will pass a sudden surge).

In trailer-lights, there's under 1 ohm (good wire or contact), around 10 ohms (good lamp), and everything else (not enough continuity to light a lamp).

In electronics, we have wires and jacks under 1 ohm, "not connected" far over 1,000,000 ohms, and a whole lot of in-between, 100 to 100,000 ohms more or less.

The dumb-beep continuity checker is great for solid connections, not for most electronics parts.

(*) The cut-off between beep and no-beep varies. Some peepers draw the line at 10 ohms, others at 300 ohms. You can try yours against a resistor assortment.
  • SUPPORTER