Conductivity Probe Survival Guide

[cshutchinson]

I had a fun weekend getting the Apex configured and programmed, and still have much to do. However, one problem plagued me all weekend. The conductivity probe!

Using the PM2, I would perform the calibration, it would look great in the cal solution, put it in the tank and it would go crazy. Now I know my salinity isn't that far off. I must have done this 15 times. Even made my own cal solution with an article from reefkeeping.com. That was fun.

I thought I had it figured out last night, was getting good salinity numbers, so I went home for the evening. Came back to check on things this morning, and the numbers for the salinity probe were crazy high! Good thing, I know I must have a broken probe.

Ok, one more try. Let's calibrate it again. Did that again and it looked great. All day in fact. Then the T5 fluorescents cut off. Crazy numbers again, but I was clued in on the problem. I searched the forum here and found this long solution about wrapping the ballasts in tin foil etc. etc. etc. No way was I doing that. Not on my beautiful light rack! The last post mentioned a grounding probe.

Hey, I have got one of those. Took it out of the package, plugged it in, submersed the probe in the tank....... what do you know, problem solved ! :dance:

Now when the T5's turn on and off the conductivity probe stays rock solid. I know this has been resolved before, but this might save someone from pulling their hair out!

Hope this helps. :jester:

 

[cshutchinson]

While I have eliminated the huge swing I was seeing , it looks like I still have a -1.0 ppt swing during the light cycle. Anyone have any ideas?

Both of the temp probes and the PH probe are not being offset by the light cycle.

 

[kurt_n]

Could it be related to having temperature compensation turned off for the cond. probe?

There was a post here within the last couple weeks regarding that issue, but I didn't pay much attention to it since I don't have that module.

 

[Deleted member 143833]

I had a fun weekend getting the Apex configured and programmed, and still have much to do. However, one problem plagued me all weekend. The conductivity probe!

Using the PM2, I would perform the calibration, it would look great in the cal solution, put it in the tank and it would go crazy. Now I know my salinity isn't that far off. I must have done this 15 times. Even made my own cal solution with an article from reefkeeping.com. That was fun.

I thought I had it figured out last night, was getting good salinity numbers, so I went home for the evening. Came back to check on things this morning, and the numbers for the salinity probe were crazy high! Good thing, I know I must have a broken probe.

Ok, one more try. Let's calibrate it again. Did that again and it looked great. All day in fact. Then the T5 fluorescents cut off. Crazy numbers again, but I was clued in on the problem. I searched the forum here and found this long solution about wrapping the ballasts in tin foil etc. etc. etc. No way was I doing that. Not on my beautiful light rack! The last post mentioned a grounding probe.

Hey, I have got one of those. Took it out of the package, plugged it in, submersed the probe in the tank....... what do you know, problem solved ! :dance:

Now when the T5's turn on and off the conductivity probe stays rock solid. I know this has been resolved before, but this might save someone from pulling their hair out!

Hope this helps. :jester:

If the grounding probe changed the reading then you still have a problem; but the grounding probe is masking it (and potentially going to cause you more problems).

IMO you should remove the grounding probe and start removing/moving wetted electrical devices until you locate the one inducing electical current into the water. Something must be leaking current into the water and locating that is important for your health and the tank inhabitance.

 

[schwaggs]

IMO you should remove the grounding probe and start removing/moving wetted electrical devices until you locate the one inducing electical current into the water. Something must be leaking current into the water and locating that is important for your health and the tank inhabitance.

I agree with Ken. I had a similar situation with a light seeming to cause voltage to be introduced to the tank but the problem ended up being a bad heater. Once the heater was replaced, turning on the light didn't cause any probems.

 

[cshutchinson]

I agree with Ken. I had a similar situation with a light seeming to cause voltage to be introduced to the tank but the problem ended up being a bad heater. Once the heater was replaced, turning on the light didn't cause any probems.

After reading your post, I couldn't sleep, so i got out of bed and came to the office to run some tests.

I removed the ground probe before any of these tests. In fact it is still out of the system.

First, I turned on all the lights, T5s and MHs and noted the conductivity reading. Then, one by one, unplugged each device in my system, noting the conductivity reading; including heaters, skimmer, etc. etc.

Then I turned off the light circuits one by one and noted the reading. Here are the results:

Conductivity with all on: 31.9

Unplugging each non-light device one by one: no change, still 31.9

Minus Right MH: 32.6
Minus Mid MH: 33.3
Minus Left MH: 34.9
Minus Back T5 circuit: 34.9
Minus Front T5 circuit: 34.9

Then I tried touching the ground probe to the hanging light frame. My light frame is suspended, with no contact with tank whatsoever. No change in reading. I also touched probe to the T5 ballast case, with no change. And, the MH reflector with no change.

Can you guys recommend a course of action now?

 

[cshutchinson]

New discovery or two.

Moving the conductivity probe cable as far away as possible from other electrical cords seems to change the reading.

The overhead light in the reef room is on the regular house circuits for the room. All the reef tank outlets are pulled directly from the outside panel and are all GFI circuits. They have their own 20 amp breakers. Three dedicated circuits.

Now, get this. Turning the overhead fluorescent light on in the room immediately changed the conductivity reading by a whopping 1.1 ppt! Turning it off reduces the reading by 1.1 ppt.

 

[cshutchinson]

Here is what I think the problem is....

Neptune is running a floating system via these USB cables. The expansion modules do not have an earth ground. With no true ground the conductivity cable is affected by EVERY electrical device emanating EMI around it.

My support for this statement lies in the fact that if you touch a true ground to the casing of the expansion connector on the PM2, these fluctuations that I am seeing go away.

Tell me if I am wrong guys. Just kind of frustrating.

I am seriously considering cracking open my PM2 and adding a true earth ground to the metal casing of my conductivity probe.

 

[jeffreylesser]

Tagging along. I had similar issues with the temp probe and MH ballasts as I am sure others have. This sounds very similar.

 

[aquamanic]

If you go to the Marine Depot website and look at the user comments for the Pinpoint salinity probe http://www.marinedepot.com/American_Marine_Pinpoint_Salinity_Monitor_Single_Item_Monitors_Controllers_for_Saltwater_Aquariums-Pinpoint_Monitors-AM1115-FITEMOID-4-vi.html, you'll see two remarks about EMI with this probe. In fact, one person said he called American Marine and they were aware of it. Granted this is a self contained monitor and probe but I think it's the same probe Neptune uses. They could verify.

My point (no pun intended) is it may be the probe, not the PM2 module.

 

[cshutchinson]

My point (no pun intended) is it may be the probe, not the PM2 module.

You are right, the PinPoint has the same problem. I feel like I just threw away $200.00.

I respect your level of knowledge here. Should i just pull the probe and not use it? I don't see how it can be useable like this and the PM2 was really intended for this particular probe right?

If you know of a better probe for the PM2 could you share the info?

The pinpoint probe doesn't really look like my lab grade conductivity probe from Neptune.

 

[cshutchinson]

No big deal. The ultimate solution appears to be to take the probe out of the tank and not use it. And....do better research next time.

Thanks for all the help guys.

 

[aquamanic]

I think I would try the grounding first and see if that works. You can always connect another salinity probe but the grounding would be cheap and easy. If it doesn't work long term you're no worse off than you are now.

Also, I would contact Pinpoint support and see what they say. I don't know if a choke or some other type of electrical suppression device might work but they would know. Just a thought.

 

[cshutchinson]

I think I would try the grounding first and see if that works. You can always connect another salinity probe but the grounding would be cheap and easy. If it doesn't work long term you're no worse off than you are now.

Also, I would contact Pinpoint support and see what they say. I don't know if a choke or some other type of electrical suppression device might work but they would know. Just a thought.

You know, a choke is a great idea! I will try and ground the PM2 via the metal plug casing surrounding the conductivity probe and will also try a choke coil on the probe lead.

Thanks for the idea.

 

[aquamanic]

Radio Shack and Home Depot

Man's Best Friends

 

[jeffreylesser]

FWIW I put chokes on not only my temp probe(I know not a conductivity probe, but I have one of those too), but on my aquabus cables as well. I got my temp fluctuations down to under a minute of odd temps when the MH come on, and the stabilized temp is the same as before the lights came on. I think with chokes you can get to a liveable point. I am intrigued by the grounding though, and I would like to hear more about it. I am sensing a DIY project for myself.

 

[schwaggs]

Two things:

1) Contact Neptune and get their suggestions.

2) If you want to ground the PM2, how about cutting the end off a USB cable and using the shield on the cut end to ground the PM2?

 

[cshutchinson]

Today, I bought chokes for every USB cable and every probe. I was not able to eliminate the delta on the conductivity probe with my overhead fluorescent lights, not to mention the halides.

I tried all sorts of combinations and just couldn't make it function close to normal.

I haven't tried grounding a spare USB port like Schwaggs suggested, as I figured a could possibly ruin an entire Apex system pretty quick over a conductivity probe that I don't have to have in the system.

I will leave the tinkering up to Neptune's engineer.

I have a handful of chokes if anyone needs one

Any more ideas?

 

[Deleted member 143833]

Two things:

1) Contact Neptune and get their suggestions.

2) If you want to ground the PM2, how about cutting the end off a USB cable and using the shield on the cut end to ground the PM2?

I'm alwasy cautious about grounding out components; devices tend to be unfriendly to having ground references chagned and grounding something may cause damage or cause things to malfunction.

Moving things further away is often the best solution (for example I have some probe variation (temp and PH) and found the cause to be induced by MHD ballasts into the EB8; moved the EB8 about a foot away and problem has never since returned).

 

[schwaggs]

I didn't intend to suggest you ground the PM2, just offering an easy way to ground it if you wanted to as opposed to tearing the PM2 apart and trying to wire something to the probe shield like you mentioned.

Where is the Cond probe in the system? In the main display, the sump, an over flow? Can you move the PM2 and probe further away from the lights? How long is the AquaBus cable that leads into the PM2?