Voltmeter 20' Long Wire Length

[jocanon]

What are the potential problems in attaching a digital volt meter to monitor a 12v marine battery voltage level on a boat with a wire that is 20' long connecting the volt meter to the battery? There are actually two batteries I will be monitoring. I am aware of voltage drop, but can't I just adjust for that or, in other words, if it reads out 12.1v I can adjust in my head knowing it is actually something slightly higher than that, in short, wouldn't the reading still be consistent, just consistently lower? Also, what other concerns are there and how do I mitigate problems arising from such a long cable run? What wire gauge should I use? Should I use twisted pair to reduce noise?

Here is a link to the digital volt meter I will be using:

Amazon.com

 

[rjenkinsgb]

As long as the wiring is a reasonable gauge, normal automotive etc. cable and not hair-fine stuff, the error should be minuscule.

The voltmeter probably draws something like 30mA, at a guess. At that, it would take over 60 foot total of 20awg wire to cause a 0.03V error.
Whatever the error is, it should be reasonably consistent, but depending on the internal voltage regulator in the meter.

The error margin is likely less than the reading accuracy or tolerance of the meter.
In other words, don't worry about it!

 

[jocanon]

As long as the wiring is a reasonable gauge, normal automotive etc. cable and not hair-fine stuff, the error should be minuscule.

The voltmeter probably draws something like 30mA, at a guess. At that, it would take over 60 foot total of 20awg wire to cause a 0.03V error.
Whatever the error is, it should be reasonably consistent, but depending on the internal voltage regulator in the meter.

The error margin is likely less than the reading accuracy or tolerance of the meter.
In other words, don't worry about it!

What about long wires acting as an antenna? I don't really know what that means btw LOL, I just head somewhere that it could be a problem for long wire runs.

 

[rjenkinsgb]

What about long wires acting as an antenna?

Just twist the wires together; that prevents any "loop" effect and mostly cancels out local interference.

 

[Pommie]

Many years ago, multimeters were quoted as 20,000 ohms per volt which meant the meter inside them needed 50µA for full scale deflection. The reading will be accurate unless you use extremely thin wire. As RJ mentioned, twisted pair will be good, available (very cheaply) as ethernet cable.

Mike.

 

[picbits]

Fuse it at the battery end as well. If you have a short to chassis ground anywhere along that wire length, it will help prevent any meltage ....