Help with Multimeter Reading

Apollo7235 · May 29, 2021

Hi all,

Please forgive my slew of threads today; troubleshooting in full swing.

I just tested my display using a multimeter and the readings never stabilized. The meter read 0 before I began the tests and continued to go back to 0 each time I pulled the probes out out of the ground and the water and dried the water probe off.

The readings either continued to rise or continued to fall. I noticed that if I so much as bumped the sensors it would cause major spikes in the reading, so I just set the meter down on the tank stand in the hopes that it would settle on a number, or at least a range for that matter, but it continued to either climb or decline.

I have the black probe in the ground of a wall socket and the red probe in the water.

What am I doing wrong?

redfishbluefish · May 29, 2021

You want the meter set for AC volts and one probe in the COM outlet and the other in the V outlet. With AC, color doesn't matter. Now set the meter to AC Volts. With newer meters, this is a V with a wavy line over it. Now you're set. One probe in the water, the other on ground. I typically use the little screw on a cover plate for my ground. You can also use the round hole on an outlet. Again, color doesn't matter.

SamBackspins · May 29, 2021

It’s my understanding that the voltage you read will have some varying readings depending on all the equipment in the tank. The magnets, motors, and such that are in your tank will be generating some voltage depending on their current state.

I believe the test for if you have “stray” voltage is just if the level is elevated in general, although it should be shifting around a bit as time changes. I don’t know the specific range that it should be in, but it changing shouldn’t be an issue.

Rmckoy · May 29, 2021

With any stray voltage .
typically because we are grounded , just putting your hand in the water you should feel a little tingle or even a stronger zap .

capted · May 29, 2021

Also make sure your meter is not set to Mv. Should be set to ac volts not ac mv.

Apollo7235 · May 29, 2021

Okay, weird update:

I am going through and testing each piece of equipment one by one, but I haven’t had any high readings; everything has been around <0.1V in difference (AC).

I decided to test my sump where I have my heater, skimmer, and return pump (obviously) and I have the weirdest results.

my Jebao wave makers are in my display, yet, when they are on, my sump reading goes from 0.022V to 0.832V ???

I guess the current can travel down into the sump, but I have the return pump off and I’m getting this reading. I tested my display with the wave makers on and only got a 0.037V difference, but this is a huge jump in my sump, right?

SamBackspins · May 29, 2021

Since the wavemakers have a motor in them I wouldn’t be surprised if they generate the largest field.

are you doing this because you’re trying to diagnose issues in the tank?

Apollo7235 · May 29, 2021

Test Results:

38-Gallom Display:

Everything Off: 0.095V

Only Return Pump On: 0.195V

Only Wave Makers On: 0.132V

Sump:

Everything Off: 0.022V

Only Wave Makers On: 0.832V

Only Skimmer On: 1.346V

Only Heater On: 0.721V

Only Return Pump On: 1.132V

Apollo7235 · May 29, 2021

SamBackspins said:
Since the wavemakers have a motor in them I wouldn’t be surprised if they generate the largest field.

are you doing this because you’re trying to diagnose issues in the tank?

Yep, going down the list of troubleshooting to figure out why my display seems to kill 95% of what I put in it.

capted · May 29, 2021

What's the total or highest reading you're getting? Any magnetic motor can induce some slight voltage.

redfishbluefish · May 29, 2021

What multimeter and what settings do you have where you're getting tenths, hundredths and thousandths of AC Volts?

By the way, It's not uncommon to have a fairly large amount of induced voltage.

SamBackspins · May 29, 2021

Most other things I’m reading where people do end up having an issue the reading is more above 30V, so I don’t think stray voltage is an issue here.

then again, that’s not very scientific, so I’d take it with a grain of salt.

Apollo7235 · May 29, 2021

capted said:
What's the total or highest reading you're getting? Any magnetic motor can induce some slight voltage.

The highest was in my sump with the skimmer on, 1.346V.

Apollo7235 · May 29, 2021

redfishbluefish said:
What multimeter and what settings do you have where you're getting tenths, hundredths and thousandths of AC Volts?

By the way, It's not uncommon to have a fairly large amount of induced voltage.

It’s a Klein Tools Multimeter (hubby had it for work in the past so I’m assuming that’s why it reads into the thousands.

capted · May 29, 2021

Looks like the meter is set up correctly. Maybe test using another outlet ground just to make sure there are no issues with the ground in the outlet your using now.

redfishbluefish · May 29, 2021

Yep, your voltage is extreme!y low. And Klein is an excellent brand....electrician preferred. I'd suggest one more test.....check an outlet. Put one of each probes in the slits of an outlet. You should get 110-120 volts.

And if you only have a volt or so of leakage/induced voltage, that's not your problem. If I could be so lucky.