AquaController pH Probe and Float Switches

[Brian Prestwood]

Hey All

My float switch is interferring with the pH probe on my AC3. When I plug the float switch in the pH reading drops from 8.2 to around 7.6. It also interferes with the ORP probe.

I tried putting a multi-meter between the tank water and ground and then plugging the float switch in to see if any voltage was flowing to ground. I get inconsistent results. It looks like there is about 0.5v all the time, float switch or not.

I used the float switches we group bought from AquaticEco...

Aquatic Eco Float Switch

about six years old. They work on the same principle as the door and window alarm sensors. There are a couple of permanent magnets in the float. I'm not sure what's in the rod the wires run into. Anyone know?

Assuming there isn't a crack in the rod the wires run into, is there any other way the float switch could interfer with the pH probe?

I'm hestitant to buy a new one until I know what's wrong with the old one.

Anyone got a float switch they are not using that I could borrow to test?

 

[xia]

Did you try moving your probes further away from the float switch and each other? Hmm ... I'm going to try pulling out my float switch, and see if it affects my ph readings.

 

[jlfnjlf]

Brian,

Are you using the float switch on your AC III? If so how are you interfacing the two? If not how are the float switches connected?What is the resistance with the float switch in the closed position? Typically interference comes in the form of switch bounce when the switch changes state. However this seems to be a fairly constant interference.

More data is needed before I can give an opinion.

John

 

[xia]

No it didn't make any difference for me. My ph meter is about 10-12 inches away and my orp is right next to it. My float switch is made by ultralife.

 

[Elite]

Brian,
Did you talk to Curt from Neptune? I had the same problem with mine and he sent me a different telephone cord. The shielded cord works much better. If you can try to mount your DC8 away from the electronic equipment.

 

[funman1]

I know that the switches from Aquahub are NOT rated to be under water.
I had to epoxy the heck out of mine because I knew when the main return pump shutdown they would become submerged.

Are you runing it low voltage (like 12 or so) or is it connected straight 120VAC?

 

[Brian Prestwood]

<a href=showthread.php?s=&postid=9611692#post9611692 target=_blank>Originally posted</a> by xia
Did you try moving your probes further away from the float switch and each other?

They were six feet apart and still did the same thing.

 

[Brian Prestwood]

<a href=showthread.php?s=&postid=9611756#post9611756 target=_blank>Originally posted</a> by jlfnjlf
Are you using the float switch on your AC III? If so how are you interfacing the two? If not how are the float switches connected?What is the resistance with the float switch in the closed position?

The float switch is currently wired into the input port of the AC3 (5v DC). It interfers even more when it is attached to 24v relay (little black box) it came with...

Marine Depot Float Switch

I couldn't plug it in without kicking my GFI.

I verified the top part where the wires go into the float switch does not have to be in the water for the interference to occur.

When the switch is closed the resistance is 0.2 ohms.

The interference occurs as soon as I plug the float switch into any power source and continues, swith on or off, until I unplug it.

FYI - Had two of these switches wired in series for redundancy...

I tried with just one, either one, and still got pH probe interference.

 

[Brian Prestwood]

Elite

I e-mailed Curt about a source for reliable float switches. I haven't heard back from him yet.

 

[Brian Prestwood]

Steve

I can see evidense of copper wire corrosion inside both of my float switches. They didn't do a very good job with the resin that seals the wires in. As with your probes, mine are submered when the power is off.

I don't think the corrosion is a factor in the interference. The float switch interferes with the pH probe even when the end with the faulty resin seal is in the water.

FYI - I rinsed the whole assembly in RO before I did this sealed-tip-only in the water test to make sure salt residue didn't conduct electricity through the faulty resin seal to the water.

I also tested it with the rod only, no float. It still interfers with the pH probe. That was a shot in the dark.

>Are you running low voltage?
These float switches are rated up to 32v. They are intended to trigger a 110V relay. My float switch is connected to the 5V DC input on my AquaController III.

 

[Brian Prestwood]

Problem Solved

Problem Solved

Problem Solved

It is the leaky resin seal at the top. When I submerged just the tip very carefully it didn't interfer with the pH probe. I did the first test in poor light. I must have submerged the resin without realizing it.

Other than the leaky resin seal at the top, the float switches seem to work fine. I'm going to seal them better and re-install them.

Thanks all for the help.

 

[jlfnjlf]

Oh I did not think about the conductivity of salt water...

Glad to hear you got it figured out.

John

 

[funman1]

That's exaxctly why I had to add extra stuff to the top of my switches because aquahub comes with a warning says switches are not submersible..

So mine are epoxy coated on the top.
Glad you got it pined down..

Now just be glad you weren't one of the ones that run 120VAC through your float switches