Measuring output power from a generator coil in a pulse motor setup ...

[qvision]

I'm having trouble measuring the output power of a coil in a pulse-motor.

I'm rectifying the output, which is 282 V.

I am measuring the voltage using a DMM, with a 10 Ohm resistor in series with the positive output of the coil and the positive input of the DMM.

I am trying to measure current and i can't, i have tried using a second DMM across the resistor and still get a zero reading.

I know there is current there because little 25mA light bulbs are lit brightly from the output.

Also, using Ohm's Law, I = V/R, I = 282/10, I=28.2, obviously i'm not getting 28 Amps from this little thing, what am i doing wrong !


Any help greatly appreciated.

DC.

[Farmhand]

Hi Qvision, if you want to measure current the current must be flowing, so if
there are lights running and there is a 10 ohm resistor before the FWBR then just
use AC volts on the meter and measure the volts across the resistor then divide
that voltage by the 10 ohms, remember to use points of volts, it must be a
decimal or whole of volt. Then measure the voltage across the AC output of the coil, and
multiply the former by the latter.

So if you see 1 volt across a 10 ohm resistor you see 100Ma then if you have
10 volts causing it you have 1 watt. I think.

Maybe if I'm wrong someone will correct me.

Cheers

[TanTric]

hmm, if you are getting 282V you have very high impedeance coil, that means you will have a very small amount of current output...

put your bulb on Load and measure the amperage in this config:

Rectifyer (+) --TO--> DMM (+)
DMM (-) --TO--> Bulb (+)
Bulb (-) --TO--> Rectifyer (-)

hugs

[qvision]

Cheers Tantric that worked a treat. Sorry farmhand i tried Tantric's way first because it looked easiest

Funny thing is, i can't seem to measure voltage at the same time with another of my DMM's, i have tried :

1. Putting the DMM across the FWBR output.
2. Putting the DMM across the 10 ohm load resistor.
3. Putting the DMM across the current-measuring DMM.

It reads zero any way i try !

I am confused

[TanTric]

Brother thats strange! You should be able to measure voltage with one DMM connected to + and - of rectifyer, and current with the other DMM in the config that i mentioned last post...

you can try to measure AC Volts before the FWBR...

Cheers Tantric that worked a treat. Sorry farmhand i tried Tantric's way first because it looked easiest

Funny thing is, i can't seem to measure voltage at the same time with another of my DMM's, i have tried :

1. Putting the DMM across the FWBR output.
2. Putting the DMM across the 10 ohm load resistor.
3. Putting the DMM across the current-measuring DMM.

It reads zero any way i try !

I am confused

[Farmhand]

Tantric is right, with high voltage the current might be hard to measure. You
might need a more sensitive meter or a higher resistance. No need to be sorry.
We all do what is most convenient to us and what works.
I'm certainly no expert. You're setup looks promising, good work. And hats off
for keeping at it when others have not.

Cheers

[qvision]

Ye, i should get an analogue meter, in fact i will get one !

I've seen a bench one for 15 quid that has good range and sensitivity.

It's taking ~ 6.75 Watts to power the device and this single coil produces 2.8, obviously there wil be losses when stepped down.

Each additional coil will add core/wire-drag which, according to previous tests, will be more than equalled with the coil, not short-circuited but with a very low ohmic load, i've only tested to 3.333 Ohms but the effect is enhanced the lower the resistance.

Next week i'll add two more coils and see what rears it's ugly head !