# Multimeter Use and Operation Training 101

14-Sep-2012

## Multimeter 101

Video Transcript

When diagnosing electrical faults, It is important to understand what it is exactly you are measuring, and the relationship between each item of measurement.  It's imperative to know why these measurements are taken in particular ways, so your results are an insight into the potential problem, and not just some mystery number on your multimeter. So lets get started, turing your Multimeter display, from this, to this.

There are only 3 measurable elements of a circuit,

• Voltage
• Current
• Resistance

Every other unit of measurement is a calculation based on one or a combination of these items. Lets take a very, very close look at what exactly these are. We can see that a circuit, like us and everything around us, is constructed from atoms and their atomic particles.

An atom, like a tiny solar system, has a Nucleus, consisting of Neutrons with no electrical charge, protons with a positive charge, and orbited by electrons with a negative charge, the unlike force attraction of the Proton and the Electron perfectly balancing the centrifugal force of the elections orbit.

The number of electrons in the outer orbit of our atoms determine the ability for an atom to conduct electricity, the more elections in the outer orbit, the stronger the balancing forces keeping them in orbit, the higher the RESISTANCE to having electrons freed. This RESISTANCE measured in OHMS

Say for example, We use a magnetic field to push one of our electrons out of orbit, our perfect Atom becomes an unbalanced ION. If an atom losses an electron a positive ion, if gains an election it a negative ION.

Lets get our magnet again and create another positive Ion, freed electrons move away from the EMF (Electromotive Force) from one atom to the next, a series of electrons moving from one ION to the next is electrical current, measured in AMPS.

If we take a large number of atoms, no more than that, that's it, we can free a large number of electrons, The amount of difference in free electrons between to points is VOLTAGE measured in VOLTS.

Lets go back out to our circuit and see how this is applied in the real world.

We have voltage, measured in VOLTS, The difference in free electrons between 2 points

We have current, measured in AMPS Current The flow of electrons at a single point

And Resistance measured in OHMS, How difficult it is to free elections between 2 points.

Lets take a look at how V,I and R interact with and effect each other.

Voltage, In terms of electrical fault finding, Voltage can not be affected by current or resistance, Voltage can only be

• too big
• too small
• perfect

Resistance, again in terms of electrical fault finding. Resistance can not be affected by current or voltage, Resistance can only be

• too big
• too small
• perfect

Current is effected by both resistance and voltage. As voltage increases, so does current flow, and as voltage decreases so does current flow. Current flow is inversely affected by resistance, as resistance increases, current flow decreases and as resistance decreases, current flow increases.

Electrical fault finding is not about finding whats wrong with a circuit, its about finding whats right, making a mental list of possible faults and ruling them out with tests, one by one.

Voltage, being the difference in free electrons between 2 points can only be measured in parallel.

Current, being the flow of electrons at a single point, can only be measured in series. meaning that you need to disconnect the circuit to allow the electrons to flow through the meter for measurement.

And Resistance, being the opposition to current flow, its always advised the components are disconnected when measuring resistance.

In the next video, we will have a look at some construction of circuits focusing on voltage, types of voyage and voltage tests.

We here at OLCT, Appreciate all feedback, good or bad, If you have got something to say please say it. 