Conductivity Probe Survival Guide

[cshutchinson]

Here is the configuration:

the cable going to the PM2 is 15'
the conductivity probe is in the sump. Moving it to the tank didn't change the EMI problem.
The pm2 is 5 feet from the closest halide fixture, and 12 feet from the MH ballasts
The pm2 is 8 feet from the overhead fluorescent light which causes EMI variation in the probe too.

My first EB8 is right beside my metal halide ballasts. This may be the problem. Here are some pictures. The PM2 you see is right over the sump. The WXM is beside the tank at the end of the sump.

 

[schwaggs]

Nice setup!

I can't tell from the pictures, where is the AquaBus cable that runs from the EB8 to the PM2 routed?

 

[cshutchinson]

Nice setup!

I can't tell from the pictures, where is the AquaBus cable that runs from the EB8 to the PM2 routed?

There is an EB8 under the tank near the floor and return pump. The aquabus cable runs from there (floor) to the wire tray behind the sump and over to the PM2.

It used to lay on the floor behind the sump, then straight up to the PM2, but no difference in the quality of the reading.

 

[aquamanic]

I see the problem. Your setup is too clean and organized! You got to clutter it up a little!

Actually, a question and a thought. First, what's the difference between picture #1 and #3. Look like they were taken at different times.

Second, joking aside, maybe part of the problem is running all those cables parallel to each other. Sometimes just crossing cables at 90 degrees can reduce inductance. Have you tried placing your PM2 signal cable and the probe outside of those wire management channels?

 

[cshutchinson]

It was comical today, I had a friend flipping the light switch off and on in the room while I move these chokes around. He had not a clue what the heck I was doing. Crazy when you turn the room lights on and off and the conductivity changes

 

[cshutchinson]

I see the problem. Your setup is too clean and organized! You got to clutter it up a little!

Actually, a question and a thought. First, what's the difference between picture #1 and #3. Look like they were taken at different times.

Second, joking aside, maybe part of the problem is running all those cables parallel to each other. Sometimes just crossing cables at 90 degrees can reduce inductance. Have you tried placing your PM2 signal cable and the probe outside of those wire management channels?

Yes, I pulled all the cables out today and moved them all over the room. No difference. I was expecting one. I was very wary to keep them away from halide and t5 power. But you see, they don't come close to any halide or t5 power cables.

Picture one was in earlier in time. Picture 3 was closer to completion.

 

[aquamanic]

Do you have a piece of metal conduit laying around you could thread the probe wire through to deflect some of the EMI?

 

[cshutchinson]

Do you have a piece of metal conduit laying around you could thread the probe wire through to deflect some of the EMI?

That's an idea. What if I wrap the conductivity cable in aluminum foil... the cable is so long..... Like 15 feet!

 

[cshutchinson]

I wonder if it would work to coil the extra probe cable, wrap it in foil, and hang out just enough to drop in the sump, but keep the foil wrapped coil dry?

I think I will go to the office and try that now. will report back.

 

[cshutchinson]

Well, sometimes even the best ideas don't work. Don't laugh! :hmm4:

 

[aquamanic]

Honestly I didn't think the aluminum foil would work. But your room is looking good now!

On the conduit, you would only need a piece that could run the couple feet between the PM2 module and your probe. You could fold the wire inside, use a couple of pieces of electrical tape to make it more manageable.

 

[cshutchinson]

Honestly But your room is looking good now!

On the conduit, you would only need a piece that could run the couple feet between the PM2 module and your probe. You could fold the wire inside, use a couple of pieces of electrical tape to make it more manageable.

Thank goodness the AF didn't work. I will get a piece of conduit tomorrow and give it a shot.

 

[aquamanic]

Here's my solution - each cable precisely positioned to maximize confusion and minimize EMI

 

[cshutchinson]

Honestly I didn't think the aluminum foil would work. But your room is looking good now!

On the conduit, you would only need a piece that could run the couple feet between the PM2 module and your probe. You could fold the wire inside, use a couple of pieces of electrical tape to make it more manageable.

Well, just to put the final nail in the coffin, an update...

I cut a 24" piece of 1/2 metal conduit and slid all the probe cable inside, leaving 6" exposed on each end to plug it in, and 6" for the probe in the sump.

The results...not too encouraging. No major changes. Still had the fluctuations when the overhead lights in the room were turned on.

So, I removed the probe from the PM2 and smiled.

Now, is it possible that I just had a bad Lab Grade conductivity probe or should these fluctuations be considered par for the course?

Does ANYONE have a conductivity probe hooked to a PM2 that doesn't fluctuate when your lighting tank lighting goes from an on to off state or vice versa?

Thanks for all the help and ideas in this thread.

 

[cshutchinson]

I can't help but thinking I could solve this problem, but I hate to keep throwing money at a sinking ship so to speak.

 

[schwaggs]

Have you contacted Neptune for their thoughts?

I have one last idea that you may not like... Try connecting the PM2 to a EB8 with the short AquaBus cable (~3 foot). Either place the EB8 near your PM2 location or place the PM2 near your EB8 location. I suspect the AquaBus is grounded and placing the PM2 close to the EB8 might help to eliminate the interfearance.

 

[cshutchinson]

I think your idea is definitely worth a try. I will report back tomorrow after I give it a shot.

 

[pencil3]

Does not happen on my two (one hooked to a EB8 the other to a PM3). If you haven't already contacted support I would as a next step.

Does ANYONE have a conductivity probe hooked to a PM2 that doesn't fluctuate when your lighting tank lighting goes from an on to off state or vice versa?

 

[mike_dani]

Any update on this issue?

 

[cshutchinson]

I have concluded that i have one of two issues with the PM2:

1. the aftermarket cable (15 feet) is causing interference problems
2. or, the PM2 has a problem

I because of all the things (digital inputs) I have wired to my existing PM2, I have decided to buy another PM2 to resolve the problem.

The only issue is that I can't find a PM2 anywhere. It appears everyone is OUT of them and have been now for over 5 weeks. I am still waiting.