Which multi meter to buy?

[justin brown]

I'm finally getting around to building my psu for my phono 3s xl. I'm measuring the resistors, but I'm finding the values are changing if I hold them whilst measuring (as opposed to laying them down on the table). A friend who has experience with electronics has suggested my mm is inaccurate, as these values shouldn't change, therefore making it very difficult to distinguish which resistor should go where. The one I am currently using I bought for general household use some time ago. It is a draper, and was only £15. I see on YouTube that all of the mms' that people use are fluke, and are much more expensive that mine.
What mms' are people using on this forum, as I'd like to get an idea of which one to go for.

Thanks.

N.b. Matthew, sorry it has taken me this long to get started, it is a bit embarrassing!

[pre65]

Are the resistors not colour coded ?

This web site (see link) includes an easy to use calculator to work out resistor values.

http://www.electronics2000.co.uk/cal...calculator.php

I would have thought even a cheapo meter would get you in the right ballpark area, croc clips on the leads might help.

[bikerhifinut]

First question is:

Are you holding the probes with your fingers on the resistor leads?
With higher values of resistor in particular, you will get a false reading due to the resistance of your own body in parallel with the resistor.

2) why are you measuring the resistors? Why not just accept the values as per the resistor colour code? It's useful to measure components when close tolerance is an issue but on the PSU I doubt its an issue.

As to meters, I do not know whether yours is a digital or analogue meter so cant comment. However I did find that the cheapo bargain basement Digital meters had issues at AC.
I eventually settled on an inexpensive Digital meter from Maplins for around £60. It does all I need and has the advantage of a True RMS reading on AC.
I also have an ancieant but serviceable Moving coil meter rated at 20kohm/volt which is very useful for valve circuitry and accurate enough for our purposes.
Last year I bought a secondhand AVO model9 meter and it has proved invaluable and robust. As i remember it cost me £50 at a swapmeet its a bargain IMHO.

Don't get hung up on fancy test gear, the Fluke gear etc is excellent and for a professional it's essential to have the robustness and build quality etc. But for most amateur purposes you'll find something to suit in Maplins at a reasonable price.

One thing to remember is that Digital meters take a bit of time to settle down when taking a reading. This can be frustrating. A Moving coil meter will more or less give you an instant reaction. This can be an equipment saver at times.
That said, you probably wont find a decent MC meter on the new market and you might do better to get a used AVO model 8 or 9 (theres nowt to choose between them) if you fancy a moving coil meter.

I'd just go down to Maplins and get one of theirs. They have useful stuff like capacitance ranges too on them.

Hope I haven't confused you too much.


Andy.

Originally Posted by justin brown

I'm finally getting around to building my psu for my phono 3s xl. I'm measuring the resistors, but I'm finding the values are changing if I hold them whilst measuring (as opposed to laying them down on the table). A friend who has experience with electronics has suggested my mm is inaccurate, as these values shouldn't change, therefore making it very difficult to distinguish which resistor should go where. The one I am currently using I bought for general household use some time ago. It is a draper, and was only £15. I see on YouTube that all of the mms' that people use are fluke, and are much more expensive that mine.
What mms' are people using on this forum, as I'd like to get an idea of which one to go for.

Thanks.

N.b. Matthew, sorry it has taken me this long to get started, it is a bit embarrassing!

[bikerhifinut]

Succint Phil.
Said it in less words than I just did!

Originally Posted by pre65

Are the resistors not colour coded ?

This web site (see link) includes an easy to use calculator to work out resistor values.

http://www.electronics2000.co.uk/cal...calculator.php

I would have thought even a cheapo meter would get you in the right ballpark area, croc clips on the leads might help.

[colin.hepburn]

A cheapo DMM should be fine really I have three for about a £5.00 each which work fine
Which have an a clamed accuracy of +/_ 1% Works fine for me

And it’s cheap to replace if you blow it up when you forget to check the last setting you just used it jumps off the bench well thou
It’s a good point if you are a beginner you may want as auto ranger


I also Have my old AVO 8

[John Caswell]

Hi all,
Do not buy an auto ranging meter as your first, because it will not teach you, and therefore you will not teach yourself, to measure voltages/current correctly by engaging brain to decide which range you should be on.
A simple cheap DMM initially is best.

John

[justin brown]

Dear all,
Thank you for your replies. Being a novice, and reading the paragraph in the build instructions to 'check the value' of the resistors, as the coloured bands can sometimes be a little tricky to read due to the colour of the resistor itself. I realise now, that I am being pedantic, and that I was hoping to avoid such basic questions on this forum. But, we all have to start somewhere, and there is no fast track route to experience. Of course, there are always questions which are not written in text/theory books, and this is where I come unstuck... At least until I have a bit more experience, anyway.
I wasn't sure how critical it was to get an EXACT reading/value, so I was treading carefully. Thanks for your wisdom, at least I can relax a bit and not be so anal.

Phil, that is a very useful device... That's the kind of thing that restores ones' confidence! I don't have any crocodile clips either... They would certainly make testing less fiddly, (and ultimately, less frustrating).

Andy, it is a DMM, and I am aware it will take a few seconds for the reading to settle down. It is an interesting point you made about holding the resistors whilst testing, as this IS what happened.

I am visiting my parents this week, so will not be able to spend time on the build. However, I have next week off before I return to work, and it would be nice if I could complete the psu, and start the build on the phono stage itself.

Thanks again,

Justin.

[pre65]

It might be a good idea to get some clip leads, they are cheap enough and invaluable.

Clip one end on the meter probe and the other on the resistor wire. Just bear in mind (for super accurate meter readings) that these leads have a bit of resistance.

Something like these.

http://www.ebay.co.uk/itm/Crocodile-...item2562854d88

PS Measuring each resistor is not a bad thing, better to spot a "dud" before soldering it in.

[justin brown]

Invaluable advice Philip. I will buy some as soon as I get back.
Another thing, how/ what do I hold the pcb with whilst I am fitting/soldering in the components? At the moment, I just have a large blob of blue tack. Ideally, I'd like some sort of desk top jig.

Thanks.

[pre65]

I use one of these, I think mine came from Maplins.

http://www.ebay.co.uk/itm/Magnifier-...item2a246b19cf

Search e-bay for "helping hands" to find loads.