ORP and ph probes affecting eachother

[nbsdsailor]

I have an AC3. I just started dosing ozone for the first time and bought a ORP probe. I have run a pH probe for a long time now and have never had any problems with them. After calibrating the ORP probe with quinhydrone 4 & 7, I checked it against the 400mv premixed solutions from pinpoint and it was pretty close.

Now, when I put the ORP probe into the tank, the pH reading drops very quickly by about .5 pH. Also when put the ORP probe in and then put the pH probe in, the ORP drops. Both probes calibrate fine. It seems like I am dealing with a stray voltage problem but I cant find any.

Any suggestions?

[rbarker33]

Sounds like a typical ground loop problem. With a ground loop (AC voltage in the water), it can attack both ORP and pH sensors, it basically uses the sensors as a grounding rod effecting the readings on both sensors.

An easy way to test to see how much ground loop you have is to get a multimeter and drop the red wire in the tank and put the black wire in an earth ground and measure the AC and DC voltage.

To correct, you can purchase a differential pH or ORP sensor or try to ground out your AC3.

Good luck.

[aquamanic]

The other thing you can do is put the pH probe in a cup of tank water, then put your ORP probe in the tank. Now they're isolated as far as the water goes. If the pH probe still reacts then you're getting some other type of interference, not through the water.

[Crackem]

I have this same problem that affects my conductivity probe every time my power compacts or metal halide comes on. I bought a multimeter and when I tested it I still got a zero ac reading. I have no idea what to do. I also put a ground probe in but that didn't help.

[Crackem]

Sounds like a typical ground loop problem. With a ground loop (AC voltage in the water), it can attack both ORP and pH sensors, it basically uses the sensors as a grounding rod effecting the readings on both sensors.

An easy way to test to see how much ground loop you have is to get a multimeter and drop the red wire in the tank and put the black wire in an earth ground and measure the AC and DC voltage.

To correct, you can purchase a differential pH or ORP sensor or try to ground out your AC3.

Good luck.

What is a differential ph or orp sensor and how would I ground out my apex?
I thought a gfci and a ground probe would take care of that.

[rockdoc2010]

Which one is the pH and ORP sensor.. one is red and the other is blue and there is nothing on either probe.. setting up for the first time.

Thanks!

Douglas

[aquamanic]

Red is the ORP probe, Blue is pH.

[nbsdsailor]

The other thing you can do is put the pH probe in a cup of tank water, then put your ORP probe in the tank. Now they're isolated as far as the water goes. If the pH probe still reacts then you're getting some other type of interference, not through the water.

This is what I am doing and it works, but I'd like to get a real time reading on my pH. Would a grounding probe help?

[Crackem]

A grounding probe is supposed to help with stray voltage. To test for stray voltage you need a multimeter. Also I believe that it is recommended that you use a gfci if you use a ground probe. I have the same issue except my light ballasts are affecting my conductivity probe and I can't believe I'm the only one with this problem, but no one has offered any ideas or a solution.

[bazineta]

This is what I am doing and it works, but I'd like to get a real time reading on my pH. Would a grounding probe help?

A grounding probe in this instance is sort of like dealing with a flat tire by just pumping air into it constantly.

Next step would be to locate the cause; basically, that means recreating the problem, then temporarily unplugging your equipment from the energy bar, and validating that the problem is gone. You then plug your gear back in one by one until you see the problem; the last piece of gear plugged in is the cause. Commonly, it'll be a pump or heater with a cracked housing.

[nbsdsailor]

Well I plugged every item in one at a time. I used a fluke multimeter and got 1 volt AC and it would randomly come and go. I installed a GFCI breaker on the aquarium circuit. Still getting the probe issue. Thanks for all the advise so far, much appreciated!

[Crackem]

Are your probes right next to eachother or are they at least 6" apart? Is there a lot of flow where you have them ?

[bazineta]

Installing the GFCI is in my opinion absolutely the right thing to do, as it could save your life. I've seen arguments from time to time here that doing so puts your tank at risk, and honestly, I admire those folks for their selflessness. In my case, if it's me or the fish, I choose me. That's just how I roll.

GFCIs generally trip at 5mA of current difference; frankly, that's not a lot, so it's a bit strange that you'd be measuring voltage in the tank but it wouldn't be tripping. Are you confident that it's correctly installed? It's very easy to get the legs reversed.

[bazineta]

Double post.

[nbsdsailor]

Pretty sure, it was dummy proof I think. Only one way to install it and there was a curly cord that ran to the neutral bus. With only 1 volt it may not have the 5mA. I am trying to think of a way to isolate and put the meter inline in the circuit to read amperage. Any advise? I think I would have to read every devise one at a time. Also from my understanding, a GFCI compares current not traveling back to neutral and assumes a direct path to ground. If I have the tank isolated from ground, it won't trip, right? Or am I way off here? Sorry for the newb questions. I guess I'll find out when I install a grounding probe.

Are your probes right next to eachother or are they at least 6" apart? Is there a lot of flow where you have them ?

They have to be 6" apart? Going to try that now. Lot of flow, they are in the sump.

[bazineta]

GFCI current delta measurement is between the hot and the neutral, yes. As you say, hard to screw up in the panel, but reversing hot and neutral at the outlet end is extremely common. One easy way to check is using one of the inexpensive yellow test plugs with three lights on them; they'll tell if you have a reversed hot and neutral at the outlet.

[nbsdsailor]

I'll check. I really should be sure, its my life. Although, that would be on the electrician that installed my wiring when the house was built. I put the GFCI in the panel.

Does ghost voltage effect these probes? Do I need to keep them away from the AC magnetic field of the pumps?