reading current on the multimeter

[mettam]

I am having trouble understanding the data my multimeter gives me when reading currents.

I believe my leads are pluged into the correct inputs; far left (black earth), and far right (red Pos).
I set my meter to 200m (the green area of the dial) and I get a reading of 6.0 and decreasing and when I set it to 20m I get a reading of .6 and decreasing.

1. So what is 20m is it .002 of a Amp and 200m is .0002 of a Amp ?
2. And how does .6 when read at 20m relate to 1 amp. ?
3. Why are these in units of 20 rather than 10 ?
4. Why does the amperage start decreasing so fast, it seems I am draining my 6v battery by doing this test ?

Thank you.

 

[Paul Obrien]

The battery is draining fast because the meter appears as a very low resistance to the battery, Never connect a ampere meter across a battery!!!
.002 =2mA
.02= 20mA
.2= 200mA
.6= 600mA or 0.6 of an Amp.

You can pick any unit you like when you build a meter but most likely the max the meter can display is 1.999 of something.
Amp named after Ampère

 

[dknguyen]

I'm kind of suprised you didn't destroy your meter- probably a low-current battery. You're lucky. What were you trying to measure anyways?

 

[philba]

I suspect the shunt can handle a fair amount of heat before it melts down. Still, not recommended for long DMM life.

You don't want to connect your ammeter to + and - of the battery but rather in series with a load. well, technically, your ammeter, the probes and the voltage source are loads but very low resistance ones.

 

[mettam]

Thanks for your replys unfortunately I am still a little confused about this.
I am reading 6V from a 9V battery and I am trying to figure out the current coming from it.

I think the essence of my question is "How do you know how many places to move the decimal".

It would appear that when the meter is set to 20mA I should move the decimal point 3 places to the right of the reading, in this case the reading was .6 so the actual number reads 600.mA
And when the dial is set to 200mA I should move the decimal point 2 places to the right of the reading, the reading was 6.0 so the actual number would be 600mA.


1000mA is = to 1 Amp ?

FYI... I think my multimeter has a 10Amp max .

 

[Dr.EM]

So it's just a maths problem?

Set to 20mA, with a readout of 0.6, you have a current of 0.6mA. Set to 200mA with a readout of 6, you have 6mA. The decimal point on the meter doesn't move, the lowest number just gets cut off. So, trying to read 2uA on the 200mA setting won't yield a result. It is all because the screen has quite few digits and you'd need a huge dynamic range to cover all the ranges as one.

1000mA = 1A yes
1000000uA = 1A

10A is the standard upper limit on multimeters, you'll probably find it has it's own (unfused?) connection. You can read up to 200mA, then it jumps to the 10A section. Reading something like 300mA is difficult to do accurately as a result.

http://en.wikipedia.org/wiki/Multimeter

**broken link removed**

 

[AllVol]

I am reading 6V from a 9V battery

Since you are using your ammeter directly across the contacts of the battery, it is realistic for the voltage to be depleted to around 6 volts.

AllVol

 

[Hero999]

Most meters are fitted with fuses you probably just need to replace it as you've probably blown it.