dmm

[dd1975]

could any of you expert sparks advise a novice on how to use a multimeter please.
i am a corgi registered plumber who mainly concentrates on installs, ie i would normally get a service engineer out to a combi breakdown if it was'nt blatantly obvious to me what the fault was. also i have been asked to repair 3 or 4 electric showers as opposed to just replacing them as normally would be the case. thanks

we are all back to mend and make do with a lot of jobs now

 

[Pensdown]

Although I'm not the expert you're looking for I can offer you a little guidance.

Before you can safely use a test instrument of any type you first need to understand what you're testing for and why. Then you need to understand the results. An electrical multi meter will test for resistance, AC voltage, DC voltage, continuity and some will do current and other tests.

For example, there's no point measuring the resistance of a heating element in a shower if you don't understand the results.

It would be the same if I measured the Co2 levels in my flue. I'm sure I could follow a few instructions and take the readings but they would mean absolutely nothing to me.

What sort of faults are you trying to diagnose?

 

[dd1975]

i think a solenoid is gubbed on a shower fitted 2 years ago and the warranty is up , that kind of thing , basics, cheers

 

[Spark123]

There are a couple of ways of testing the electrical side of the solenoid, the easiest way is simply with a solenoid test pen which is basically a reed switch, LED and battery.
Being extra carefull, with the power on and in the state at which the solenoid should be energized hold the pen next to the solenoid and go all around it to see if it will light up. If this does light up then the fault is mechanical.
If it doesn't light up you could test the voltage going to the coil to see if the supply is present, this could be 240vAC or a smaller DC voltage.
If there is no voltage there then the fault will be with something electrically upstream of it.
If there is voltage there then likelyhood is the solenoid coil has burned out, you can test the resistance of the coil by (power off first) and disconnect the solenoid. Test across the solenoid coil using ohms range.

 

[dd1975]

cheers

 

[jockspark]

hi it may be easier to come back to the forum and get advise on tests
as they come up ie soliniod would be a continiuty test set on ohms
its hard to try and explain how and when to use the functions on a multimeter in one post unless someone else wants to have ago

 

[Spark123]

I probably forget I work with solenoids a lot
Honestly though, the easiest way to test a solenoid is with one of those pens but they don't like being dropped - got plenty of replacement reed switches in stock
Don't mistake it for a voltstick though!

 

[ericmark]

When my son started I lashed out and got him a clamp on meter.
This is because if the meter can be set to measure amps through the leads and you have it on this range when you try to measure volts it can cause ionisation of the atmosphere. That means the air it's self starts to conduct and you get a big bang. Using leads to GS38 with fuses in does reduce the risk but a clamp on in most cases will no have any range where it is a short circuit so safer.
Also clamp on meter will allow some remote reading for example around the wire supplying the motorised valve you can get some idea if its working without being at the valve.
As already talked about the magnetic sticks are good the ones which do both volts and magnetic seem to be more sensitive.
Also important to know when things are dead and the test instrument for this should not rely on batteries or being on correct range the martindale tester fits the bill here you should also have a proving unit one job I did it was instant dismissal if caught without proving unit but in most cases you can stick in socket to prove.

 

[Taylortwocities]

In that case check the voltage on the input to the solenoid.
You would use the AC volts range on your meter for that.

Got volts? How many? 230ish, Thats great!
Does solenoid operate? No, then its the solenoid.

But Pens is right, You need to know the principles of electricity and what to expect.

So: suppose an immersion heater isnt working.
You would use the volt range to check if power is going through the stat and onto the element.

The next step is to check contimuity of the element. You would use the resistance settings on the multimeter. But you would need to know what the result needs to be so you can then determine if the result is correct.

So, what should the resistance be? You need to know that so you select the correct setting on the meter. And also if the reading is correct.

Well, the heater is rated as 3KW (3000 watts). You would use Ohms law formula to work out what the resistance should be.

By using Ohms Law you will know that

P = V² / R

And you know P and V, so by formula transposition you should end up with

R = V² / P

R = 230 x 230 / 3000 = 17.6 ohms

So, you need to know all this stuff to be able to understand whats going on....

What, watt