Perhaps I should have clarified my question a little.  The standard "amps measurement" capability of DMMs are less than 1A in most cases.  With the name "ammeter", I was referring to meters that can measure the higher amps that are usual in RC applications (10A to 40A is common, can go much higher too). 

So I was wondering about Karthik's suggestion that the need for resister load setup was just a DIY thing which adds no value compared to "out-of-the-box" functionality in common DMMs

Quote from: dileepbalan on July 12, 2010, 06:08:16 PM
But I feel limitation, because we can measure only 10A.

with the miltimeter i got for Rs 100/- i can measure DC voltage upto 1kv
current upto 20Amps
AC voltage upto 750v
+ resistance and other miultimeter functions +it has a mode in which it emits sound when the resistances between the leads is less than 100 ohms ,i think a circuit can be made out of it to test the LiPo voltage using it as a LiPo alarm by using ohms law       R=V/I     keeping I(current) constant the resistance will purely depend upon the voltage of battery in our case a LiPo...experts please comment

Quote from: anwar on July 12, 2010, 06:28:22 PM
So I was wondering about Karthik's suggestion that the need for resister load setup was just a DIY thing which adds no value compared to "out-of-the-box" functionality in common DMMs

thanks Mr Anwar but the multimeter i have seen till now measure voltage upto 20amps will search in market for better ones with higher values.....

regards

kartik

Quote from: speedracer on July 12, 2010, 09:27:05 PM

Quote from: dileepbalan on July 12, 2010, 06:08:16 PM
But I feel limitation, because we can measure only 10A.

with the miltimeter i got for Rs 100/- i can measure DC voltage upto 1kv
current upto 20Amps
AC voltage upto 750v
+ resistance and other miultimeter functions +it has a mode in which it emits sound when the resistances between the leads is less than 100 ohms ,i think a circuit can be made out of it to test the LiPo voltage using it as a LiPo alarm by using ohms law       R=V/I     keeping I(current) constant the resistance will purely depend upon the voltage of battery in our case a LiPo...experts please comment

Some major points:

1. The "continuity test" actually feeds a voltage through the resistance and sounds an alarm if the resistance is below a certain threshold.

2. If you have a constant current source you will need added circuitry. The voltage drop across the LOAD will be inversely proportional to its resistance. Your meter,   the "load" in the mode above, does not behave like a simple resistance and you may well damage it by the voltage from the LiPo flowing into it!

3. The voltage drop across the terminals in the 20A current mode can be quite high. Also the resistance of the leads themselves can be significant. In short, not recommended to use your meter for this function.

I've already bought a multi meter..Can i use tat?

Quote from: xxkrishxx on July 13, 2010, 01:44:44 PM
I've already bought a multi meter..Can i use tat?

Pls explain what do you want to use it for.

Copy of my message posted earlier without Pic

i read through the forums and evaluated various options to make a shunt resistor.

Then i tried with local Electrical shops for the 14 gauge wire and found surprise on their faces.

Then another rcgroups search i found an easy way to make a shunt is buy resistance. So the resistance required was supposed to be .001 Ohms. Now most of the electronics shops don't store these kind of low value. So as advised by the forum. i bought 0.01 ohm(2w) X 10 and put them in parallel which means i got 0.001 (20W).  Now this setup should be ok till about 200Amps. Woof. Cost of 10 resistors was only 30 bucks. Also i bought two banana plugs to mount the resister directly on the voltmeter.

Connect this in the series to the Battery and measure the voltage across the shunt. The setting is 200mV and the output will directly show the current consumed.

This setup will cause extremely low loss to the setup and also no confusing Amp calculation.

Thanks to all the forum in and outside india, i am a happy person with a home grown AMP meter.

Regards Especially to Astha ji .

Picture shows a simple setup of 0.001Ohm resistance to measure current in excess of 200amps

Cost
Resistor - 30 ( For 10 nos)
balloon plug - Rs 10
Dean - Own stock
wire - Old Burnt ESC

@ hangingtough.

Kewl connector

Do you have any way to check how accurate the current measurement is with your connector ?

QuotePicture shows a simple setup of 0.001Ohm resistance to measure current in excess of 200amps

I think this is what you meant. => The full scale when you put your knob to 20mv with this connector would be 200A.

Using the 14 AWG shunt will inc the range. But then there will be calibration issues.
Using 10x0.01 Ohm is a good way of doing I suppose. This may not require any tweaking for the calibration at all.

Using the $3 Wattmeter switch and this connector can have a perfect home RC Wattmeter.

The 14 AWG is approx 2mm-sq. Could not find this in the local market.
I got only 1.5 and 2.5 mm-sq wires.
Using 2.5 mm-sq I think we can go up to 50A.

How much will those banana plugs take ? I think 15A but i'm not sure.
I was thinking of putting a 3.5mm Gold bullet connector if my amps was above 20A.

What fuse does your MM have ?

re living the past as requested by some members

This is with reference to "Drone"s post #32:


Using 10x0.01 Ohm is a good way of doing I suppose. This may not require any tweaking for the calibration at all.

Not quite true. Stray resistances from the wires, connectors could well add a significant amount as compared to the 1 mOhm of the resistance.


The 14 AWG is approx 2mm-sq.

14 AWG is app. 2 sq. mm and NOT 2mm. sq. (which would be 4 sq. mm.)


How much will those banana plugs take ?

The banana plugs are not carrying any of the main current and, therefore, will not make any difference if they  are gold plated or otherwise.


What fuse does your MM have ?

Again, not relevant, since the current is not flowing through the meter wires.