RE: DMM Question. Have I done something wrong?

["James Hoye" <yahoo@xxxxxxxxxxxxx>]

> I bought myself a new DMM from B&Q (A rapitest MAS830L) which
seems
> fine. I went to try and measure the current of my cordless phone by
> connecting the probes to the battery whilst the phone was on. I got a
> reading but a few seconds later the phone went dead and the batteries
> were very warm! I let them call down and all was well. Was I doing
> something wrong whilst trying to test the current?

Well, to test current, your meter needs to be in SERIES with the device you
are measuring.

You need to effectively break into one of the leads powering the device, so
that the power flows THROUGH the meter.  The ideal current meter has zero
resistance, ie. it appears "transparent" so that it does not
alter what it's
measuring.

It sounds like you connected it ACROSS the battery thereby creating a short
circuit - hence the batteries getting rather warm.  You use this method for
measuring the VOLTAGE (since an ideal voltmeter should have an infinite
resistance).

Please don't try this on mains unless you are absolutely certain of what
you
are doing!

James