Shielding probe wires

[Jeremy King]

I was reading a thread where it seemed like the reefer moved his pH probe wired, and the reading came up 0.2. That made me wonder. This kinda sounds like the probe was picking up noise that was throwing off the reading. I know bubbles can mess up probe readings, and maybe having them in low flow areas, but is electrical noise that common? As an electrical engineer, I can see where all those wires I run all over my aquarium could be causing cross-talk and noise. None of them seem to be LVDS or shielded or have any other protection from outside influence.

Tldr; Should I be shielding the probe wires for pH, salinity, ORP, O2, etc?

 

[GoVols]

@Brew12
Do you want to take a shot at this one?

Thanks, Freddie

 

[zachxlutz]

I know that Neptune recommends keeping the salinity probe wire away from all other power cords and wires. That presents a problem with the way my system is setup. Following along for ideas on how to shield the probe wires without having to re-route things.

 

[cope413]

Cheap and easy shielding - wrap the wire in aluminum foil, and then put a layer of heat shrink tubing (or other wire wrap of your choice).

 

[Brew12]

I was reading a thread where it seemed like the reefer moved his pH probe wired, and the reading came up 0.2. That made me wonder. This kinda sounds like the probe was picking up noise that was throwing off the reading. I know bubbles can mess up probe readings, and maybe having them in low flow areas, but is electrical noise that common? As an electrical engineer, I can see where all those wires I run all over my aquarium could be causing cross-talk and noise. None of them seem to be LVDS or shielded or have any other protection from outside influence.

Tldr; Should I be shielding the probe wires for pH, salinity, ORP, O2, etc?

Yup, electrical noise can be an issue, especially for those who use DC pumps.

You don't necessarily need to shield them if you are careful with your cable routing. All your wires for pH, salinity, ORP, O2 and temp can all be run together. If you can keep them a few inches away from any power cables, that would be best. You can minimize the impact by having any power cables cross at a 90 degree angle. Otherwise, as @cope413 suggests, you have a few options for easy shielding options.

 

[cope413]

Also, if you don't want to shield, or can't, you can help reduce noise by not running wires parallel to each other. If wires need to cross each other, make it a perpendicular crossing if possible.

 

[Jeremy King]

Wrapping the wires seems like too much work, since I'm going to be pulling all of the probes out to clean and calibrate periodically. Even the pumps get pulled out and cleaned and/or replaced from time to time, so there is no such thing as a permanent installation. I was thinking some cheap 3/4" electrical conduit might work, but that would be hard to feed probes in and out when I want to calibrate or replace them. I did find this stuff (https://www.pentairprotect.com/en/hoffman/clean-tray-type-1) which would work I suppose. You'd have to ground the metal conduit or duct work.

I think the easier way would be to put a couple screw hooks on the back of the stand to hold them, and make sure to keep the power and signal wires away from each other, unless crossing at right angles. This will also help with my being OCD about "Wires must be routed together and look pretty!!"

And I do have the salinity probe ~4" from the others, but held in in the same probe bracket. (Salinity on far left, then temp, then titanium grounding probe, then ORP, the pH. maybe an extra blank in the middle, too.)

Thanks for the info!