Resistor values.

Thread Starter

Techmasteruk

Joined Oct 13, 2016
51
IMG_0411.JPG I know this should be easy one for you guys, but not for me :(

I don't know if I'm reading this resistor value correctly, is it a 50 Mega Ohm ? Or 50 Ohm ?
 

Thread Starter

Techmasteruk

Joined Oct 13, 2016
51
Looks that way to me. Do you own an ohm meter? Measure it. The resistance is so low it will probably read as zero (or a few tenths of an ohm in your test leads) because most meters can't measure that low.
Thanks #12, I used my ESR Meter reading 0.028, I guess it's working properly ?IMG_0412.JPG
 

#12

Joined Nov 30, 2010
18,224
By using the wrong meter you have introduced an AC component. The reading of 28 milliohms says the resistor is outside its tolerance range, but the resistor looks perfectly OK from the outside. Please use a real ohm meter or just assume that a very low resistance reading means the resistor is good.
 

Thread Starter

Techmasteruk

Joined Oct 13, 2016
51
By using the wrong meter you have introduced an AC component. The reading of 28 milliohms says the resistor is outside its tolerance range, but the resistor looks perfectly OK from the outside. Please use a real ohm meter or just assume that a very low resistance reading means the resistor is good.
 

Thread Starter

Techmasteruk

Joined Oct 13, 2016
51
It always help Travm.

I've shortened the leads on the ESR meter, I now have a 0.057 reading. That's tell the resistor is good. Oh well I'll have to continue my investigation to find the shorted components.
 

MrAl

Joined Jun 17, 2014
11,389
Hello there,

With a resistance that low you dont normally use an ohm meter, you use a test current and then measure the voltage across the resistor.

With this value you can use a 1 amp DC test current. When you measure the voltage with a digital volt meter you should read close to 0.050 volts.

If you use one meter for the current and another meter for the voltage reading you can divide the voltage reading by the current reading to get the resistance:
R=v/i

where v is volts and i is current in amperes.
 

Tonyr1084

Joined Sep 24, 2015
7,852
3W ? Three watts? If it's 50 mΩ then it would be able to handle 0.387 volts and 7.75 amps. 7.75 • 0.387 = 3 watts

If it were 50 MEG Ω @ 3 W, calculations suggest a voltage of 12,247.5 volts at a current of 245 µA. I don't see that little device handling 12,000 volts.

My numbers come from calculating the voltage by taking the square root of [3watts (times) 0.05 Ω]. With a known voltage, dividing 3 watts by the voltage you get the amperage. To check the math I multiplied amps (times) volts and it took me back to 3 watts.

My confidence on my numbers - um - does not exist. If I've figured this wrong - someone let me know please.
 
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Tonyr1084

Joined Sep 24, 2015
7,852
I think I'm troubled by the very low voltage and high amperage. I've also calculated that if I had my numbers reversed, say 7.749 volts and 0.387 amps then the resistance should be 20 Ω. NO ? ? ? If so - the wattage would still be 3 watts, but the resistance would be on an order of 400 times off from 0.05. (0.05 x 400 = 20)
 
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