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Reduced resistance of resistor

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engrguy42:
Okay, science project time...  :D

I have a 0.5 ohm, 100 watt resistor. Applied current and voltage via my bench power supply, and got consistent values of 0.595 ohms.

Checked my multimeter...leads shorted gives an ohm reading of "0.0". Measuring the resistor gives a reading that stays pretty much on "0.6" but occasionally bounces down to "0.5".

So...hell, I dunno...I guess the only bit of useful info from that is if you want some accurate ohm readings at that low range try using your bench supply and a calculator since it will probably give V and I values with at least 3 digit accuracy? 

GlennSprigg:

--- Quote from: Twoflower on April 12, 2020, 09:34:08 am ---Everything is fine with that resistor. The letter 'R' shows the decimal point of the value:
R56 = 0.56 Ohm
5R6 = 5.6 Ohm
56R = 56 Ohm

So the value show on your meter is OK as with such low resistance values you have to take the resistance of the cables and such things into account. For example connect the cables together and you'll most likely see a value > 0.

--- End quote ---

Twoflower said it all. The 'R' replaces the decimal point, for readability !
This also caused some confusion over the decades, when photo-copied "Blue-Prints" of German circuitry showed 'Commas' instead of full-stops between numbers, as the 'dot' would often be lost in such old prints. Like... 25,6 Volts...

Twoflower:
The commas in Germany are still used as decimal point. To be honest I don't know what the exact background of this difference is. The Wikipedia shows Germany is not the only one :-)

There's some additional potential pitfall: For German people
1.000 + 2,000 = 1.002,0
Solution to that: In Germany the point is optionally used as the thousands separator. In english that would translate to:
1,000 + 2.000 = 1,002.0
Confusing, isn't it?  8)

And with this the thread is officially derailed (but hopefully answered).

engrguy42:

--- Quote from: Twoflower on April 12, 2020, 01:13:56 pm ---The commas in Germany are still used as decimal point. To be honest I don't know what the exact background of this difference is. The Wikipedia shows Germany is not the only one :-)

There's some additional potential pitfall: For German people
1.000 + 2,000 = 1.002,0
Solution to that: In Germany the point is optionally used as the thousands separator. In english that would translate to:
1,000 + 2.000 = 1,002.0
Confusing, isn't it?  8)

And with this the thread is officially derailed (but hopefully answered).

--- End quote ---

Yeah, lucky guess  :D

But how about my questions about multimeter accuracy with resistance?

Siwastaja:
Just never ever use either , or . as a thousands separator and there is no problem. Even if you ignore the international aspect, both symbols look too much alike and can be mistaken ("100,000.00" and "100.000,00" visually suck even if both are technically well defined in some countries).

Use spaces instead - both "100 000.00" and "100 000,00" are unambigious to anyone, regardless of language background.

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