First of all , Thanks Lucien for such a great thread ..

https://www.rcgroups.com/forums/showthread.php?t=393591

Inspired by above thread , started making Wattmeter for measuring Watt requirement of Ampere eater brushless motors.

Local multimeters available in market can measure 10 ampere approx . So for measuring high Ampere's , we can use electric shunt .

A shunt allows the measurement of large current values directly measured by placing it in series with the load so that whole current to be measured will flow through it. In order not to interfere with the circuit, the resistance of the shunt is normally very small. The voltage drop across the shunt is proportional to the current flowing through it and since its resistance is known, a voltmeter connected across the shunt can be scaled to directly display the current value. Shunts are rated by maximum current and voltage drop at that current.

So for making a simple locally available shunt , Copper wire can be used . We will make a .001 Ohm shunt so that direct readings can be seen on multimeter display.Also ,for accuracy , try to take readings in least time (15-20 seconds) .

I looked for 10 AWG Single strand Copper wire here and ended in 12 AWG Copper single stranded wire which is good up to 40 Amperes ,enough for small and medium planes ( In local market , 12 gauge wire is also known as meter wire for it's use in hacking meters so sad )

Diameter of 12 AWG Copper single strand wire is  2.05232 mm and resistance per 12000 inch is 1.588 ohm .

For making .001 ohm shunt , we require exact 7.56 inch of copper wire .

So , Cut around 8 inch of wire so that exact 7.56 inch of copper wire will be available from one connector face to second connector face which is equivalent to 1mOhm or 1mV/A shunt .

Connected one end of shunt to female XT 60 (for connecting ESC )and other to XT 60 male ( for connecting battery ) .

Now connect red cable from DMM to battery side connector face exactly at face and black cable from DMM to esc side connector exactly at face . In short , Connect both cables from DMM exactly 7.56 apart from each other . Also try to wind shunt wire bifilar , so no inductance .

Move knob to lowest voltage reading (mine is 200mV ) and Wattmeter is ready for measurement .

Hope we can also give some good DIY works to RC World and RC groups .

Thanks

If someone have wattmeter , will try to test it's accuracy by comparing it with another one readings..

Aditya
I have a wattmeter and have been contemplating to do something similar, but after the 390124 projects that I already have on hand

You are welcome to use my wattmeter for testing your setup

GS

Quote from: aditya on August 02, 2014, 08:33:53 PM
If someone have wattmeter , will try to test it's accuracy by comparing it with another one readings..

@aditya
Well done. Nice jugaad!

BTW, comparing different measuring instruments may not serve much purpose.
My 2 lipo checkers and wattmeter (and even Tx display) usually differ by around 0.1-0.2v.

My method is to use one instrument consistently for comparisons, despite the fact that it may be only 90% accurate. Comparisons of readings taken by different instruments may not be valid.