Intrepreting multimeter results

[Rosco's Reefs]

I have been battling what many think is a stray voltage problem in my tanks.  Weird pH probe readings, salinity probe being off etc.  I purchased a digital multimeter from Home Depot and am trying to figure out what it means when I use it.  Using it for testing AC it has two settings, 200V and 600V.  

 

I have two tanks, nothing hooked up to them right now but main pumps (eheim 1262's). When I test one tank I get a reading between 1.0 and 2.0.  Testing the other tank returns the same value.  One of the tanks has a grounding probe on it, and if plugged in, it comes out as 0.00.  The only real difference between the two settings is decimal point accuracy

 

What readings should I see? Can anyone help me understand all of this?  Thanks in advance.

[Origami]

The meter should have two probes. One red and one black. The black probe should be plugged into the socket marked COM. The red probe will probably be plugged into the socket  marked V or V-Ohms.

 

Put the meter first in the AC mode. Pick the 200VAC range if this is the lowest range that you have. If the meter has a Volt-Ohms switch, make sure that it's set to volts. Insert the black probe into an the bottom opening (the earth ground) of a wall socket (the sort of rounded hole). Make sure it makes contact. Put the red probe in the tank water and read the meter. The scale on the meter can be complex. One of the scales probably goes up to 200. This is the scale that you want to read from.

 

After you've read the AC voltage, I like to follow up with a DC voltage check. This is a different setting on the meter. Just dial over to it and take the reading. Make sure that the scale you read from is matched to the range that you selected on the multimeter's dial.

 

It might help if you posted a picture of the meter or a link to the model.

[Rosco's Reefs]

thanks Tom.  I will do all this to make sure I am doing it right.  Now, what does it mean? I get the 1.0 to 2.0 without a grounding probe, 0.00 with the grounding probe, and 0.00 if the pump is turned off.  Do I have a stray voltage problem? 

 

Here is the meter:

 

http://www.homedepot.com/p/Commercial-Electric-Digital-Multimeter-MAS830B/202353293#.UdhJdvnbOSo

[Origami]

No problem that I can see from your readings.

 

(Sent from my phone)

 

 

[Rosco's Reefs]

last question, and thank you, BTW.  What readings WOULD I SEE if there was a stray voltage problem in these tanks?  Again, thx!

[Origami]

10, 20, 30 or more volts would be reason enough in my opinion to go looking for a source.

[Coral Hind]

The reason the reading goes to zero with the probe in is because it is bleeding off any induced voltage. When you are testing you have one probe in the tank water and the other should be grounded, like to the ground hole on a grounded outlet or a nearby metal pipe. Is that how you are doing it? As for you voltage question. It isn't just the voltage that you need to worry about since the amperage is what kills, but reading voltage indicates there is an issue. I have seen tanks with up to 30v from induced magnetic loads but were not dangerous. If you do get a reading of 90v or more that is an instant red flag.