• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Multimeter question.

Status
Not open for further replies.

rippa32

New Member
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?
 

ericgibbs

Well-Known Member
Most Helpful Member
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.!!
 

rippa32

New Member
What do you mean across?

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

rippa32

New Member
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."
 
Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
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.
 

rippa32

New Member
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.
 
Last edited:

colin55

Well-Known Member
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.
 
Last edited:

ericgibbs

Well-Known Member
Most Helpful Member
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.!!:)
 

rippa32

New Member
Yeah, the fuse was what came with it, so I assume its the right one. Everything else seems to work fine too. Also I know which one to get too. Thanks for the help.
 

Boncuk

New Member
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
 

Attachments

Last edited:

Boncuk

New Member
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. :mad:
 

rippa32

New Member
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
Thanks for all that info, I understand what went wrong now. Also thankfully it is just a blown fuse, I checked it.
 

AlainB

Member
Hi,

A few years ago, I was claming to be the fastest fuses blower east of the Pecos. Faster than my shadow, I was! A fuse a day, almost!

Checking some current, then some voltage = Poff...!! "S&#$"! Forgot again!!

Now I am older and wiser.:)

I check a current then immidiately after, really, I mean immediately after, I put back this bloddy red wire into his voltage hole.

Alain
 
Last edited:

ericgibbs

Well-Known Member
Most Helpful Member
Thanks for all that info, I understand what went wrong now. Also thankfully it is just a blown fuse, I checked it.
hi rippa,
I did say the fuse had most likely blown when I replied to your first post.

Many of us have done the very same thing, :), always check that the meter is set to the correct mode before measuring.
 

audioguru

Well-Known Member
Most Helpful Member
On Energizer's website they have a datasheet for their 9V alkaline battery. It is shown to supply 500mA for half an hour.
Into the almost dead short of a current meter it might supply 2A for many seconds.
 

JimB

Super Moderator
Most Helpful Member
Oh for the Avometer!
There must be a few of us here old enough to remember.

No fiddling about moving the leads around to measure current (only if you wanted to use the 2500volt range).
No fuses to worry about, just a mechanical cutout which open circuited the whole meter circuit if you overloaded it.
Overload in this case was when the meter needle was driven hard upscale or downscale.

JimB
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top