Ph Probe Issues - Please help troubleshoot

tmoore103 · Post by **tmoore103** » Sun Jul 31, 2016 10:44 am

Hey Guys,

So my ph probe is driving me crazy! I'm really hoping you guys can help me troubleshoot this. It hasn't really worked correctly since February. It was consistently reading less than 5 and sometimes 0. After I did some digging on the forums here I learned that they don't really last that long and I think my probe and RA unit were about 6 months old at this time, so I thought this might be the issue. I replaced the probe, calibrated the new one put it in the tank and it immediately got a reading of 3.44 without the reading ever changing. After doing a little more searching on here I came across some people having issues because of stray voltages so I decided to try this angle. I found a voltage reading of 48v when I measured the tank with a DMM. This however turned out to be a ghost voltage as I was only measuring 1.6v with an analog meter. I was unable to trace the 1.6v down to a single piece of equipment, other than my ups back up power supply at least. If I unplug the back up power supply the voltage in the tank drops to zero, not sure why. To be on the safe side I added a couple of ground probes anyway and even order a new probe just in case the voltage messed up the other one. This time I ordered one of the double junction lab grade probes hoping I could be sure the probe was not the issue. I even measured the current on the probe to make sure no current was actually passing through it and it was indeed at 0 amps. The probe calibrated fine outside of the tank but when I put it in, again it read on the low side. This time it is reading in the 5.17 to 7.6 range at least but it also isn't holding it's value with any stability. I measured tank water outside the tank and it read 8.0. Since I have ground probes installed I don't think a stray voltage is the issue. Maybe the 48v ghost voltage was messing up the probe before but now the tank is at 0v to ground. Now I'm stuck and all out of ideas. If anyone has any please shoot them off. I'll try posting the chart of my Ph so you can see how it's bouncing around.

Reef Angel Web Chart.pdf: (47.34 KiB) Downloaded 474 times

Thanks,
Tori

cosmith71 · Post by **cosmith71** » Mon Aug 01, 2016 2:49 am

What happens if you stick the probe in a cup of tank water?

tmoore103 · Post by **tmoore103** » Tue Aug 02, 2016 9:00 pm

It read normally in a cup of water outside the tank. Looks like it was a float switch after all. Really weird because I didn't measure a voltage difference when I unplugged the float switches. The first time around when I unplugged everything one by one the ph remained stuck at 3.44 so I couldn't tell it was a float switch that was causing the issue. When I replaced the probe the ph reading with the new probe read low and moved all over the place but at least it wasn't just stuck on one reading. I decided to try unplugging everything one by one again and the ph reading raised a little and stabilized this time when I unplugged one of the float switches. Strange that I couldn't detect a change in voltage with my Fluke meter though. Hopefully this helps someone else.

cosmith71 · Post by **cosmith71** » Wed Aug 03, 2016 5:35 am

You won't always be able to tell with a meter. Our pH probe is a much better indicator of stray voltage.

OceanWolf · Post by **OceanWolf** » Sun Aug 21, 2016 5:03 pm

I had a similar issue. My Led lamp for the cheato started to get moisture in. The ph meter was out of whack. I couldn't figure it out for a while what it was until the lamp stopped working. I bought an outdoors lamp this time.

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