Multimeter Mini-Tutorial

[Dedman]

Thanks Doc, Just what I need to go trouble shooting tomorrow

[tonyw]

Good on you Doc, well done.

I carry my meters around everywhere, each one is setup for individual tasks, i dont have time to mess around with settings. Saves me doing anything more than turning on and maybe switching 1 notch or 2, but it gets expensive having a few of them.

[fender3x]

On continuity, the test for ground/earth is also a continuity test that you can do with a cheap meter.

Set the meter on one of the ohms settings and turn it on. It will register 1 with the test leads not touching. When you touch them together it should register close to 0. Touched together is continuity. So, to test the continuity of a wire, touch one lead to each end of the wire. If it registers close to 0 it's good. If the register stays on 1 you have a break.

Sent from my SAMSUNG-SM-N900A using Tapatalk

[DrNomis_44]

If you only have an older style Analog Multimeter you can still use it to do Continuity Tests, all you need to do is switch it to a low-Ohms range, such as X1, or X10, then touch the two probes together, then use the Zero-Adjust to Zero the Meter-Needle, you can then test for continuity as per a Digital Multimeter, Continuity will be indicated by the Meter-Needle ending up fairly close to the Zero mark on the Meter Scale.

[fender3x]

I love those old analog meters and often use them for testing continuity. When you have it you really see the needle zip across the meter.

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[DrNomis_44]

I love those old analog meters and often use them for testing continuity. When you have it you really see the needle zip across the meter.

Sent from my SAMSUNG-SM-N900A using Tapatalk

Yep, in some ways I reckon the Analog Multimeter is better for doing Continuity Tests because they usually have a 1.5V battery inside them which is used to provide the test-current when measuring resistance, Digital Multimeters do a similar thing but the test current is smaller due to the fact that Digital Multimeters typically have an input resistance of about 10 Million Ohms so that there's no loading on the circuit being tested, on the other hand an Analog Meter's input resistance can be something like 10 or 20 Thousand Ohms per Volt, this will load a circuit being tested.

[Muzza]

A visual explanation of Volts, Current and Resistance...

[DrNomis_44]

A visual explanation of Volts, Current and Resistance...

Cheers Muzza, that is a great diagram for explaining Voltage, Current, and Resistance, another analogy is to think of water flowing through a pipe, the Voltage would be the pressure that's forcing the water through the pipe, Current would be how much water is flowing through the pipe at any one point along the length of the pipe, and Resistance would be the diameter of the pipe, so, if we decrease the diameter of the pipe (increasing Resistance) the water will have a harder time flowing through it than if the pipe was bigger in diameter, if we had a large diameter pipe (low Resistance) and increased the pressure (higher Voltage) forcing the water to flow through the pipe, then more water would flow past a given point along the length of the pipe (higher Current).


This goes to show that Voltage, Current, and Resistance are inter-related in an Electrical Circuit, as Ohm's Law states:


E (Voltage)= I ( Current) X R ( Resistance)

[fender3x]

I have always heard the water analogy, but I have to admit that I really like:

Kicking-guy = stuck-in-tunnel-guy + guy-pulling-rope

[DrNomis_44]

I have always heard the water analogy, but I have to admit that I really like:

Kicking-guy = stuck-in-tunnel-guy + guy-pulling-rope

That "+" should really be an "X".



I didn't really intend to include some mathematics with this mini-tutorial, I really wanted to keep it relatively simple to understand for people new to Electronics, but at some stage you're probably going to have a situation where knowing Ohm's Law, and how to work with it, will be useful, and, or, essential.