Thread: Multimeter question.

Originally Posted by rippa32

I have just bought a bunch of stuff to get into making circuits and was playing around with the multimeter, to get used to how it works. I tested a 9v battery fine (came up with 9.6v) but when I tried to do amps nothing came up, regardless of what setting I had it on. Am I doing something wrong?

On some multimeters, the +test lead plugs into a different hole in order to measure amps.

Also if you have tried to measure amps by connecting the meter across a 9V battery, you could have blown the internal protection fuse.!!

What do you mean across?

Also I don't think I have blown a fuse as everything else still works fine.

Originally Posted by rippa32

What do you mean across?

Also I don't think I have blown a fuse as everything else still works fine.

The fuse would only affect the current ranges - how did you connect the meter when trying the current ranges?.

Originally Posted by rippa32

Same as I did for voltage.

That was 'across' the battery then - and if the battery can supply enough current, it would have blown the fuse.

Would a 9v battery supply that much current? Ugh, it never actually explained this in the manual I got with the multimeter.

EDIT: I just re-read the manual and it actually says to "Connect the test leads accross the source or load under measurement."

Originally Posted by rippa32

Would a 9v battery supply that much current? Ugh, it never actually explained this in the manual I got with the multimeter.

Meters don't come with a five year electronics course, you're supposed to know what you're doing?.

As for the amount of current, it depends on the battery type - a NiCd one can supply a LOT of current.

Originally Posted by Nigel Goodwin

Meters don't come with a five year electronics course, you're supposed to know what you're doing?.

As for the amount of current, it depends on the battery type - a NiCd one can supply a LOT of current.

It's just alkaline. Oh and the fuse on the multimeter is .2A if that helps.

The fuse has blown. Just get a thin strand of wire from a piece of hook-up flex and solder is across the ends of the fuse.

Originally Posted by rippa32

I'll probably just replace the fuse. Would I have damaged anything else?

If the original fuse was the correct rating, the meter should be OK.

Use the correct type of fuse.!!

Hi Rippa,

before you experience severe trouble with your multimeter take a look at the attached circuit which is drawn in three possible conditions.

It's quite easy to see that Ohm's law is one of the most important when dealing with electricity.

Assuming an inner resistance of almost zero Ω a shorted 9V-battery (also shorted by an ammeter) might deliver a current of 900A at a resistance of 0.01Ω of the ammeter (theoretically).

Voltmeters are correctly wired across the load resistance to measure the true voltage drop (without losses within the cable), while ammeters are connected in series with the load resistor. Their resistance must be as low as possible to avoid any additional voltage drop because of resulting erroneous voltage drop readings across the load.

If you happen to connect your multimeter parallel to a supply source using the 10 or 20A range you might prepare to purchase a new one. (The fuse is only used for the 200mA range in most DMMs.)

Boncuk

Originally Posted by colin55

The fuse has blown. Just get a thin strand of wire from a piece of hook-up flex and solder is across the ends of the fuse.

That's a well known Turkish and Thai way to repair fuses.