Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Zero resistance and infinite resistance

Corrosio

New Member
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

Active Member
Wire gauge R per foot -

1652298897503.png


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.
 
Last edited:

danadak

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

1652300478190.png


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

New Member
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

Active Member
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.
 
Last edited:

chumijibranki

New Member
The information you shared above is great. I have been reading all details you described here. In this you described very well. If I want any more guideline I will contact you here
 
Last edited:

Latest threads

New Articles From Engineer's Garage

Top