A voltage is a potential difference between two points. All voltage measurements are from point A to point B. On a DMM the voltage is from probe tip to probe tip. It helps to have good probes.
Read the full replyI've been trying to find some info on this on google... but I just keep finding sites on DMM and how to measure voltage with them... but my question is... how does a DMM manage to read a voltage without access to the common point of the circuit your measuring?
If anyone knows of a good website that explains that could you please point me towards that... I can't find one.
Thanks!
A voltage is a potential difference between two points. All voltage measurements are from point A to point B. On a DMM the voltage is from probe tip to probe tip. It helps to have good probes.
It's like a tape measure; it measures the distance (voltage) between any two points. And like a tape measure, there's no available "zero" point to make absolute measurements from. We sometimes use a chassis, or the earth itself as "ground", but that's still arbitrary.
John
It's hardly arbitrary when measuring a voltage drop across a component.
Generally, it's seldom arbitrary.
So, what is the absolute voltage of Planet Earth?
John
"panfilero"
** Try:..... Phil
Look here:
Never give up hope!
Merely count the number of protons in the earth, and subtract the number of electrons.
Multiply that by 1.6e-19 to get the net charge on the planet, in colombs.
Divide by 708e-6, the capacitance of Earth in farads.
And there you are.
ftp://jjlarkin.lmi.net/Exit201.jpg
John
Don't use the circuit common.
DMMs are differential measuring instruments by design.
Graham
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