Stray Voltage in Tank and Probe Accuracy

[balloonpilot]

I've been fighting with my tank, trying to find reason(s) as to why I can not raise any Acro's in my tank. After establishing that the chemistry is on target, another board member suggested testing for stray voltage.

So I took out the digital volt meter and found that my tank was carrying 40 volts (yes Forty). Obtained a titanium Ground Probe and took care of that. Although I'm still trying to trace down what gear is actually causing the voltage.

Anyways - My concern is...

1) What affect does this stray voltage have on the readings various probes attached to the Profilux are reporting?

2) If I had a ORP probe (which I think measures in milivolts) - How would this be affected by stray voltage in the tank.

3) Does using a Grounding Probe mean that I can not use the ORP probe?

 

[AQD_ottawa]

stray voltage will have all sorts of issues with probes, but GHl probes normally do not suffer too badly with this due to the high design.

I would seriosuly find what component is giving 40volts in your tank and remove it fast!

 

[balloonpilot]

Yes - I agree... Simply putting a Grounding Probe in the tank seems like putting a bandage on the situation rather than fixing it.

So I took the tank apart last night, un plugging each power-cord one at at time and could not make voltage go away. Then I took all plugs out of all power bars - no change, unplugged all power bars - no change. Actually there was a change! The voltage rose from 40V to 58V...

Got down to the only thing left plugged in was the Profilux IIEX and the Profilux Dosing Pump. Unplugged the dosing pump - No change... Voltage remained now at 58volts measured from the main tank to 'good ground'.

Unplugged the Profilx - Voltage went away. Plugged it back in = 58 volts measured in the tank.

On my Profilux - I've got pH, Temp, Salinity probes and two level switches for my ATO. One at a time, I took the pH, Temp, and Salinity probe out of the tank and left them out - still 58 volts with Profilux plugged in and the level sensors "in the water" ---

Could there be this big of a 'potential difference' between the Profilux and Ground and its coming via the level circuit? Doesnt make sense because I thought Profilux operated via 12 volt power supply.

I'm hoping that I've missed something, done something wrong, etc.

Any suggestions?

 

[AQD_ottawa]

The ProfiLux is grounded for starters and yes only run on 12V even 14 V will blow it sky high so it is not the ProfiLux 100% its physically impossible.

My guess is the stray voltage is coming from a ballast this is the usual culprit.

 

[AQD_ottawa]

The level sensors have a 5Volt power line also.

I think you are reading things wrong for sure.

Furthermore if you had 58Volt loose in the tank the fish would be dead due to shock and you would get quite the belt also.

 

[balloonpilot]

Ive double checked my work...

Yes - Ive read about balast and heaters being the usual cause. Under my testing, I removed (unplugged not just turned off) everything from my A/C source except for the Profilux and measured 58volts between tank water and ground. If I unplug the Profilux voltage goes away - If I put a ground probe in it goes away.

I too would expect to have fish for dinner - but perhaps its extremely low amps and not causing any mortal issue with the fish. I have in the past noticed fish will shake sometimes (almost as if they have a chill).

Since this doesnt make sense, and I cant explain where 58volts is coming from on a 12/5 volt source... I'm just stumped because Profilux was the only thing plugged into the wall.

 

[AQD_ottawa]

how are you reading the voltage in water as just putting a volt meter in the water will not give you any reading, my only other guess is that you are reading milivolts, now that will make sense.

58Volt up the back side of the Profilux will fry it to bits I can assure you

5.8 Volt will make more sense if there was a break in the float switch line.

opticals work on 12 volt

 

[balloonpilot]

Im taking a digital volt meter, one lead (red) placed into tank and other lead is attached to known good ground.

I will double check again on the 'scale' - its auto sensing.

Also interesting is that when I only have Profilux plugged in I get the 58, but as I start to plug in other devices (pumps, lights) the voltage drops - With everything plugged and and tank in normal operations this voltage drops to 40. When I apply the grounding probe this voltage drops to 0.015 volts

 

[AQD_ottawa]

I am sure you will find the answer but to reasure you a 12V device that only has a 12V input physically can not produce 58 Volts.

If you are still worried just measure the output of the ACDC power supply, it will read around 12V, and the ProfiLux has no ability to step up voltages.

 

[balloonpilot]

Update -

I confirmed that readings are correct on my DVM (Digital Volt Meter) and the reading fluxuates between 40 and 58 volts.

But here's the strange thing... Its Gone !

Yes, I removed the grounding probe and still no voltage. So I moved on to something else (changing Profilux setup) that required hooking my laptop to the comms port on the Profilux. Laptop battery was dead so had to use wall charger --- Once I hooked the laptop to the Profilux and the charger into the laptop - Bingo 58Volts. Disconnected comms port and goes away.

So by itself - the Profilux is NOT the cause of this stray voltage! I'm relieved.

But Im not sure why or how I'm getting voltage from the laptop, over the comms port, into Profilux and into tank.

I will probably play with this more this weekend as I dont like not having a diffinative answer

 

[AQD_ottawa]

unearthed comm port in the laptop going into the profiLux -

BAD IDEA!!!!! Earth your laptop!! or make sure the comm port is tied to earth!!

We have seen fried ProfiLux's with this!

 

[balloonpilot]

So if I take a wire from ground, put a "ring-lug" connector on it and ground the casing of the DB-9 (Comms Port) that should take care of this?

I'm thinking I'll put this on the Profilux side so that the comms port is always grounded regardless of what computer I attach to it... Ok?

Or - Is there something "special" about the communications cable from Profilux that would point me in a different dirrection and put the grounding wire on the other end (computer side).

 

[AQD_ottawa]

as the issue is with your laptop I really can not advise what to do, that would open a whole can of worms.

You will need to speak with your lap top manufacturer on how to resolve a non grounded component inside the laptop.

But as you have ordered a P3 upgrade (i think) you will be switching to LAN most likely so you have no concerns

 

[balloonpilot]

Yes - Version 3 upgrade is on order (from Progressive).

I guess I'll reduce my laptop connections to a min. until V3 arrives and consider myself lucky that nothing has happened so far

Just glad it wasnt an issue with Profilux.

Laptop is owned by work so hands are kinda tied with that one as well.