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Salinity making me nuts
Posted: Tue Apr 30, 2013 5:39 pm
by Smotz
Hi all,
My salinity is calibrated with a refractometer to 35 ppt (possibly a bit more). I calibrate my salinity probe in in for over an hour but when installed, ra keeps reporting my salinity as dropping (slowly). Almost immediately its at 34.9 but an hour or so later it'll be at 34.3 - e few hours later 33.8..etc.
Help?
Salinity making me nuts
Posted: Tue Apr 30, 2013 5:49 pm
by lnevo
Check for stray voltage. Put the probe in a cup of tank water and see what happens
Re: Salinity making me nuts
Posted: Tue Apr 30, 2013 5:53 pm
by enigma32
+1 lnevo
Also, could the temperature of your water be changing during that time period? I think temperature is not taken into account in the standard code right now...
Salinity making me nuts
Posted: Tue Apr 30, 2013 6:07 pm
by lnevo
Not by default...good point though. Smotz, any correlation by chance?
Re: Salinity making me nuts
Posted: Tue Apr 30, 2013 6:12 pm
by rimai
Also, make sure that there is no bubbles either...
Bubbles tend to collect in the tip of the probe, which causes it to keep dropping.
Shake the probe inside the water.
Re: Salinity making me nuts
Posted: Wed May 01, 2013 6:11 am
by Smotz
+1 on the bubbles - My probe holder is built in to the same compartment as the protein skimmer and the microbubbles was throwing the conductivity probe way off - the fluctuations were crazy - had to move it to a different chamber (the fuge - low flow). That annoyed me but stabilized it.
Temp fluctuates +1/-1 throughout the day.
The cup thing pretty much did the same thing - as I said the salinity drops over several hours.
I am leaning towards me not calibrating it for a long enough time. Maybe I should let it calibrate for 2+ hours.
Re: Salinity making me nuts
Posted: Wed May 01, 2013 12:25 pm
by Smotz
...seems to of stabilized...
Re: Salinity making me nuts
Posted: Wed May 01, 2013 12:32 pm
by rossbryant1956
My unit has been doing this from day one. I did calibrate it carefully, moved it around to various places in my sump, etc., and yet the performance has been the same. Here is graph from the portal:
That is about a 24-36 hour slice of time. And there are no programmatic events happening at either the high or the low that causes a trend to reverse.
I did put the probe in a glass of water and the readings did stabilize and I agree that I have stray voltage in my sump (whatever that is) but have no clue what to do next.
My sump has two heaters, a main pump, a ph probe, and a temp probe in it. Do I just take out one thing (a heater?) and watch it a while? Then put it back and take out something else?
Your advice would be quite welcome. Thx
Re: Salinity making me nuts
Posted: Wed May 01, 2013 7:23 pm
by rossbryant1956
I found this article on the problem, will probably try as soon as this weekend:
Identifying, Locating and Curing Stray Voltage in a Saltwater Aquarium
How To Identify the Voltage Leak Source
By Stan & Debbie Hauter, About.com Guides
Whenever electric appliances are used in close proximity to saltwater aquariums, the potential for problems increases dramatically. Fortunately for most saltwater aquarists, a vast majority of equipment used in conjunction with an aquarium is of high quality and seldom fails. However, when an appliance does fail and leaks electricity into a tank, it is called "stray voltage".
Stray voltage, even in small amounts, can cause a number of subtle or dramatic problems in an aquarium.
How To Test for Stray Voltage
Purchase or borrow a voltage meter. They can generally be found for less than $20 at most automotive parts or hardware store.
Turn the selector to "120 AC Voltage".
Insert the tip of the black probe into the third or "grounding" hole in an electrical outlet.
Insert the metal tip of the red probe into the tank water.
Watch the meter needle for any movement. Any needle movement indicates a voltage leak in your system.
How To Identify the Voltage Leak Source
One at a time, disconnect each electrical appliance (heaters, pumps, lights, chiller) associated with your tank, retesting for voltage as described above after each unit is disconnected. Heaters and pumps (powerheads) are the most frequent cause of voltage leaks.
How To Solve the Voltage Leak
Replace (recommended) or repair the faulty unit. Test the tank once again to make sure that you have eliminated the problem.
Install a simple grounding probe in the tank to avoid damage to the tank inhabitants. This may temporarily take care of the symptoms of stray voltage, but it does not cure the cause of the problem.
Many aquarists test their tanks for stray voltage on a regular basis as a part of their normal tank maintenance routine. Detecting a voltage leak problem in its early stages can help eliminate or reduce problems in the future.
Re: Salinity making me nuts
Posted: Wed May 01, 2013 8:42 pm
by enigma32
That all sounds like a good idea to me.
I don't check for leakage too often in my system, but I do have a ground probe installed and everything hooked into a GFCI.
Just remember to not be holding on to the voltage meter probe while unplugging things
Re: Salinity making me nuts
Posted: Mon Jun 03, 2013 9:21 am
by thekameleon
One thing to remember the measurement of voltage is potential not actual current flow. Also you can't get rid of stray voltage completely. The fact that you have motors running in the water, current alternating in the water (e.g. AC cord to heater), any kind of magnet, other probes (Some use current to determine the reading) and anything living in your tank will produce some kind of electricity (Yes all living things are little power plants). Granted hopefully it is as small as possible.
I think the best idea is to figure out how you can isolate your measurement from your tank.
EDIT: I just removed my grounding probe to check my tank and I have 300 mV AC rolling around in there. I think that is pretty normal considering I have 7 pumps and 2 heaters plus 8 power heads.