Stray current question

[spicytuna]

So I had my multimeter out this morning testing some batteries and I figured why not test my tank. On the low DC voltage setting I was getting .050v so I unplugged my grounding probe and re-tested and it came back .080v. Is this normal or do I have current leaking from somewhere?

 

[aguila88psi]

I think so, its probably a heater or power head, good thing you have the grounding probe

http://saltaquarium.about.com/od/aquariummaintenancecare/a/aastrayvoltage.htm

 

[BlueCoast]

most likely normal. Testing can be tricky. You need a very high quality mulitmeter to measure properly. Most household multimeters are not accurate enough and what you are seeing as a result is more or less a rounding error.

Stray current and stray voltage are two very different things. Your tank will always have some stray induced voltage. Pumps, power lines, heaters, lights, transformers all put out stray voltage. Go hold a fluorescent tube under a high voltage line and watch it glow, that is induced current. It is not enough to harm you, but is enough to excite the phosphors in a lightbulb.

personally, I do not run a ground probe, I do not want to create an easy path to ground. I would rather isolate my tank and force the current to work harder(increased resistance) to find a path to ground.

 

[spicytuna]

:deadhorse:

most likely normal. Testing can be tricky. You need a very high quality mulitmeter to measure properly. Most household multimeters are not accurate enough and what you are seeing as a result is more or less a rounding error.

Stray current and stray voltage are two very different things. Your tank will always have some stray induced voltage. Pumps, power lines, heaters, lights, transformers all put out stray voltage. Go hold a fluorescent tube under a high voltage line and watch it glow, that is induced current. It is not enough to harm you, but is enough to excite the phosphors in a lightbulb.

personally, I do not run a ground probe, I do not want to create an easy path to ground. I would rather isolate my tank and force the current to work harder(increased resistance) to find a path to ground.

Grounding probe is really just for my safety. I was shocked once by a 60 watt octopus nw110 pump and that scared the hell out of my. After some reading, I don't think I correctly tested my tank. Tonight I will try re testing again.

 

[BlueCoast]

Here is a document from Fluke, one of the better known companies on the topic
of measuring stray voltage.


http://www.fluke.com/Fluke/usen/community/fluke-news-plus/ArticleCategories/DMMs/Stray+Voltage.htm

 

[spicytuna]

Here is a document from Fluke, one of the better known companies on the topic
of measuring stray voltage.


http://www.fluke.com/Fluke/usen/community/fluke-news-plus/ArticleCategories/DMMs/Stray+Voltage.htm

Hey thanks for the help.

After testing correctly, I had no DC voltage, but 3.4v AC. Finally narrowed it down to a DIY LED light I use for actinics. The light is attached to a clamp on fan on my tank, and a small trail of salt creep from the heatsink, to the fan, to the glass, to the overflow box caused the voltage. Glad it was an easy fix instead of having to buy a new heater or pump.