Multimeters for beginners




Safety
It's important to get a reliable and safe meter, you have to remember that one day it will save your life if working with higher voltages.
Don't forget to get some good test-leads, I personally use rubber insulated leads as they are more robust and will take some abuse, the PVC cables are less flexible and can easily crack exposing the conductor. When testing live mains voltages, always connect the meter to the neutral side of the power first, if you connect to live first you are at risk of getting a shock from the negative lead of the meter. When checking a circuit is dead, prove the meter is working on a known live output, but still proceed with caution.
You could connect to a circuit and turn it on and off a couple of times to ensure you have the right circuit.

If you are going to try to measure the resistance or continuity of something in situ for example in a radio, first do a voltage check to see if it's safe for your meter, you don't want a charged capacitor to discharge into your resistance ranges, or a faulty on/off switch to be providing power,



Choosing the meter and test-leads
Take a look around some good sites, you should find a selector chart like this and be able to see what functions you actually need, a basic Fluke meter will cost about 100, if this is too much, there are cheaper versions, just be aware of what you are buying.

Once you find the right meter, check to see what accessories they provide which can be bought later, you may have to search other sites, but make sure they will work with the chosen meter.
The sort of accessories you may want in the future :-
- Clamp adaptor (this is for measurement of AC current, and is my preferred method)
- DC current adaptor (uses a 'hall effect device' ) -There's also some AC/DC clamps, so best of both worlds, but you may be limited by the size of conductor you can clamp onto
- Temperature probe
-Pressure and vacuum probe
-High voltage probe, this is a probe that has all the voltage reduction in the probe, for instance a 15KV probe has a 1000:1 reduction, important to get a good make of probe for this, I think the reason should be obvious.

It's worth browsing here to get an idea, then looking around for similar products that are more in your price range, be sure they will attach to your meter before purchase, and don't risk a cheap product where your safety is in question as in mains or high voltage.

And of course a good set of leads, you should get a set (or more) that will have standard probes, alligator clips, and if doing electronic work there are long probes that have a grip on the end to get into tight spaces.
You'll usually get a set of standard probes with the meter, but it doesn't hurt to have other sets.
Here's an example of what is available

Remember to check your leads for damage regularly, I usually make a habit of running my hand along them (as if to straighten them out), you can easily tell if something is not right.

Using the meter (general rules)
Always be sure the meter can handle what you are testing, be sure to check any warning signs in the manual or printed on the meter.



If you look at the warning triangles on the image above the rating for the 20 Amp terminal is 10Amps constant, or 20 Amps for a maximum of 30 seconds.

Next to that the 2 Amp terminal states a maximum and that it has a fuse, this fuse (if you blow it) is a special one that you need to purchase, and is a pain to change.
Between the right hand sockets there is a warning not to exceed 1000 volts DC or 750 volts AC, that's not just between terminals, but also in relation to ground.
This restriction to ground is because of the insulation of the meter and the leads, this is why it's important to get good test-leads.

For the voltage and current ranges it is best to start with a higher range and work your way down, remember that you are most likely to be using the meter on faulty equipment, so that equipment may not be working within what is stated in the manual, prepare for overvoltage or overcurrent. it's also likely that voltage or current will be ok, but then to develop a fault that exceeds your meters ratings.

The frequency ranges should be good up to the rated AC voltage, and depending on sensitivity may not show below a certain voltage, check the manual for limits.

All the other ranges should be ok to have a play with, you just need to get used to 'scanning' for the most appropriate display, I always like to get a whole number and a decimal for accuracy.

What can you test to get used to using the meter
Start simple, get some batteries, learn about polarity.
Also with the batteries you can get a small lamp and wire in series to try the current range (amps) While you have the lamp you can measure it's resistance, knowing the resistance and voltage, you can see if the current measurement is right.
How about unplugging a simple appliance (vacuum cleaner or portable fan) and check the resistance. If you have a meter with capacitance ranges you can find some old electronics and test those.

Get used to using the meter safely before trying anything with higher voltages, you need to be sure of yourself so that your hands don't shake when you first apply the leads, if you've watched the video you will see that it is safe as long as you follow the rules.

Clamp meter or Clamp Adaptor tips



As mentioned in the video, if you want to constantly measure current, you should get hold of a 'current transformer', these are made especially for control panels, and the correct meter should be purchased to go with it.
Here is an example current transformer (CT) which shows it suitable for use with a 5Amp fsd meter
This would be a matching meter , as you can see the fsd is 5 amps, and the scale range is 0-200 amps.

A word of warning whether it be the clamp on's or the CT's, never leave the output of the CT or clamp open while current is flowing, with the higher currents you could generate a high voltage which could break down the insulation of the coil and burn it out.







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