Zero resistance and infinite resistance

[Corrosio]

Hi.
I want to warn you in advance that I am not an electrician. Electricity is just my hobby and here at electro-tech-online.com I want to improve.

I wonder if it is possible to identify a short circuit (circuit) based on the resistance of the cable to ground ??
The multimeter can display the value "OL" as an open (or also as an infinite circuit). Does a resistance near 0 ohm indicate a short circuit?
Thank you. I welcome any explanation.

 

[danadak]

Wire gauge R per foot -

So if you had a run of 100' 10 gauge then it would read ~ .1018 ohms which many low cost
meters cannot do accurately. And thats if one probe is at 100', one at 0'. In other words if you
are trying to do this at a socket then you have to account for R in the ground path. And that
would be low as well in this example. This is just not a good way to determine a short. Note I
am not an Electrician.....

You have to have a decent ohmmeter to read low R values, what model do you have ? Read its
operating/user manual to see what accuracy yours has.


Regards, Dana.

 

[Corrosio]

Míra drátu R na stopu -

View attachment 137043

Takže pokud byste měli běh 100' 10 gauge, pak by to bylo ~ 0,1018 ohmů, což je mnoho levné
měřiče neumí přesně.

Pro čtení nízkých hodnot R musíte mít slušný ohmmetr, jaký model máte?


S pozdravem Dana.

Brand: UNI-T,
model designation something like UT191E Pro

 

[danadak]

Notice the resolution is .1 ohms so using a meter for your intended purpose,
in general, not a good idea.

Add to this measurement attempt junction boxes in the path, and the resistance of screw connections,
old ones with more oxidation add to problem, as well as wire strain on the connection with
poor contact/compression.


Regards, Dana.

 

[Corrosio]

Notice the resolution is .1 ohms so using a meter for your intended purpose,
in general, not a good idea.

View attachment 137044

Add to this measurement attempt junction boxes in the path, and the resistance of screw connections,
old ones with more oxidation add to problem, as well as wire strain on the connection with
poor contact/compression.


Regards, Dana.

Thank you very much for the factual advice.
I'm sorry, but I don't understand these parameters about measurement accuracy.
What exactly do these values mean?

 

[danadak]

Accuracy is basically the deviation of something measured from its actual value.

So say you have a 1.000 reference voltage. Exact to +/- .001 volts (1 mV). Its sold to
a spec of +/- 1 mV. So it can be anywhere from .999V to 1.001 V. Lets say its exact and 1.000V
But your meter reads 1.005 volts, so its off by +.005 volts. Normally these are expressed in
percentage. So the meter is off by + .5% since it read high. If it had read .995 V then it is off by
- .5%.

Note if your meter reads to 1mV, eg. the rightmost digit on its lowest scale, we say it has
a resolution of 1 mV. So if the reference was actually 1.0001V you would never know it was
.1mV high because a 4 digit meter (x.xxx) cannot distinguish that small a voltage and display it.



Regards, Dana.

 

[Erin Barrett]

Hey, I just got a comprehensive understanding of electrical resistance with this insightful review of zero resistance and Infinite resistance from this post. https://www.electro-tech-online.com/threads/the-unit-of-sinuanonoche-resistance-posting.14646/

I need to learn about their practical applications and their role in controlling the flow of electrical currents.


Thanks