Can someone help explain continuity testing

[midiman]

Hi I am new to electrical work and I have invested in a multimeter to test components of boards.

My meter has a continuity test function. I have read up on it but some of it still doesnt make sense to me.

1. When I put my negative probe to a ground point and then touch a pin or hole on the board. Does it mean that when the buzzer sounds I have made a live circuit. And that component is supposed to be connected to the board?

2. What does it mean when I,m supposed to be testing for a short circuit. I presume if I had shorted the circuit I wouldnt hear the buzzer?

3. What if I test a part of the board and I get nothing. As in a post hole where a DC jack goes. Does that mean its not supposed to be part of an electrical circuit?

Thanks

 

[malcolmsanford]

There you go everything you wanted to know about continuity but were afraid to ask

Multimeter Tutorial - Learning about continuity

 

[midiman]

There you go everything you wanted to know about continuity but were afraid to ask

Multimeter Tutorial - Learning about continuity

Thanks.

So if I touch put my negative to a ground on my board and then touch any other point. If I get an audible bleep it means that they are connected together somewhere.

And if I dont it means that they are not connected in any way.

But if I did get an audible beep from something that was not supposed to be connected then it would mean I shorted it somehow i.e soldering.

Thanks

 

[telectrix]

you seem to be getteing the idea. keep at it and things become clear with practice. continuity between 2 points means that they are connected by a conductor of some sort. the lower the reading you get, the lower the resistance between the 2 points is. might be an idea to buy a few cheap resistors from, say, maplins and see what they read .

 

[midiman]

Please see this pic for what I mean.

I am grounding my probe on the motherboard hole marked with the green arrow.

All the points marked with purple set off the alarm. And the point in blue doesnt.



There are no visible tracks connecting any of the points in purple together. So how are they creating a circuit.

I get the part about a point on a pcb that is joined by a track to another point.

But in this jack example there are no visible tracks.

 

[telectrix]

that's because all the points are electrically connected, either through the printed track ( which is probably on both sides of the board ) or through a component. if you look at the display on your multimeter, you will see different values . ranging from say, 0.1 ohms upwards. any reading below a certain value ( could be anywhere up to around 100 ohms, depending on the meter ) will cause the buzzer to bleep. hope this helps you understand a bit more. a good idea is if you know an electrician or electronics geek, would be for him/her to demonstrate the use of the meter.

 

[midiman]

Thanks it does.

While I cant see any connection between them. I will assume like you say that there must be a connection somewhere or else how would the buzzer sound.

Boards are complex and what I cant see mifs me sometimes.

Thanks

 

[telectrix]

when your eyes get as old as mine , mate, you'll struggle to see the board, never mind tiny tracks. LOL.

 

[DoBBY]

Thanks.

So if I touch put my negative to a ground on my board and then touch any other point. If I get an audible bleep it means that they are connected together somewhere.

And if I dont it means that they are not connected in any way.

But if I did get an audible beep from something that was not supposed to be connected then it would mean I shorted it somehow i.e soldering.

Thanks

In simple terms, if you connect probes end to end of 2 conductors and press test and you get a result you have proved continuity.

 

[Golden_Boy]

Thanks it does.

While I cant see any connection between them. I will assume like you say that there must be a connection somewhere or else how would the buzzer sound.

Boards are complex and what I cant see mifs me sometimes.



Thanks

Dont forget that some boards can have 5 6 or even 7 layers of print. Dont expect to see ANY circuitry that makes any sense.

 

[mayfair]

Better to use the ohms settings rather than the buzzer setting