Lighting interference w/ pH pen

[cr500_af]

Just an FYI:

I had trouble with very inconsistent readings when using my probe (a Milwaukee PH51) in the top of my tank when the lights were on. At the time I was running T5s and blamed it on the ballast being so close to the probe.

I usually check my pH in a container removed from the tank (before I use that water for parameter tests), so today happened to be the first time I've dipped it in the top in a long time. Now I have halides with the ballasts four feet away.

I got three readings one after the other... 3, 44 and 50!

Anybody else experienced this?

Moral: don't use these near your lights if you want a good reading. Luckily it was so ridiculous that I knew it was acting goofy; it could be bad if it was only a little off.

 

[ichthyoid]

Barry,

Just curious, so a couple of questions...

1) is your T-5 ballast electronic
( I'm assuming yes, as I have not seen any magnetics )

2) is your reflector 'grounded' ?

Thx

 

[tgray3]

I use a Hanna hand held PH meter. I've got 2 T5 2 bulb retros with the ballast mounted in the fixture (Coralvue's) when i dip the tester it's probably no more than 6 to 8 inches from the ballast. I get the same consistent reading doing it this way as i get when i take some water out and test away from the tank.

 

[ichthyoid]

This sounds to me like possibly either:

1) electical interference (electronic ballast- notorious for producing electrical 'noise' especially if no ground plane/grounded reflector is used), or
2) low batteries, or
3) bad probe, or
4) stray tank voltage, possibly heater or ph is bad

Does it work ok away from the tank? If yes, it's not #2 or #3, and possibly #1 or #4.

Does it work with lights off? If yes it's #1, if no possibly #4

If still no, replace batteries.

If still no, then maybe a bad probe.

 

[cr500_af]

Probe works wonderfully in the sump or away from the tank, as well as with lights off. I'd already checked the batteries and made sure the probe itself was OK. It worked fine near LilRobb's T5s but not with mine. It freaks out near my halides or DrNecropolis' halides also. I check my tank for stray voltage regularly.

I knew it was electrical interference, just wanted to pass it along in case somebody is getting funky readings.