salinity monitor

[boxfishpooalot]

I tested my salinity after receiving my new pinpoint salinity monitor. I calibrated the meter with the 53ms vial it came with let it sit for 2 mins to temp compensate. Read to 53ms but it jumps around. It says +/- 5%?

Anyways i checked my refractometer(milwalkee atc) and at its current calibration the salinity of the vial shown 1.025 . Then i decided to calibrate it to 35ppt.

After checking the tank salinity with the refractometer the salinity shows 1.025 . Ok that seems good.

But after checking ms with the pinpoint the tank reads an astounding 38ms or 1.018. Whoa!

Should i believe my eyes?

I tested the water in a cup same thing 38ms. I shaked the probe, same thing 38ms.

When calibrating i used a measuring cup, but the calbration fluid was not completly covering the probe but most was covered. Could this be the problem?

Anyways what should i believe, refract or salinity monitor?

[Randy Holmes-Farley]

You need to make sure there are no bubbles on the conductivity probe. That might be part of the answer. So if you now put it into the calibration fluid it still reads 53 mS/cm and the tank reads 38 mS/cm?

What temperature was the fluid? The temperature compensation of the probe is not perfect, but the error is a few mS/cm for a reasonable temperature difference.

[boxfishpooalot]

Ok i recalibrated it again. This time its pictorial explanation to be sure you can see exactly whats going on.


Here is the clenex box i used to wipe the probe dry of any impurities to preserve the calibration solution.



Here i am wiping it clean


Here i am wiping the inside dry


Here is the solution in the measuring cup. Its about 3/4 cup.


Here is the probe sittin in the calibration for 2 minutes exacly set on microwave timer.


Here is the temp. It looks like 76f . I then calibrated it to 53ms/cm.



Here it is calibrated spot at 53, but it jump from 52.6 to 53.6 or somthing. Just so happened to be exaclty 53 at time of flash


Heres what it readin in the tank after a minute.


Heres the probe sitting in the sump.

[loudell]

Try a battery instead of the AC Kit....

[boxfishpooalot]

ok tried the battery same thing. 38ms/cm....

Im begining to think that this thing is accurate.

What should it read if i add 1 cup of Instant ocean salt to 2liters of water about?

I just cant believe my salinity is so low.... Maybee thats why-

-my unicorn tang died for no apparent reason
-a cleaner shrimp died in 1 day(but maybee 70ppm nitrate did it)


I have a blue linkia starfish thats been alive 4 months and a sea urchin that long.

I made Randys calibration solution and it read 45ms/cm..... While my refractometer reads that solution at a little under 1.026 .

[Billybeau1]

Hi Box,

If you calibrate your refract with the pinpoint 53 fluid, what do you get ?

[boxfishpooalot]

I get 1.026 bit under maybee 1.0256 .

[Billybeau1]

If your refractometer (calibrated with pinpoint 53 solution at 35 ppt) is good, I would trust that measurment.

This is not an exact science like we would hope for, but I have found that calibrating my refract with the pinpoint fluid, you show, gives me results I can rely on. Thats what I would trust.

Happy New Year

[Bryan]

The monitor is prone to stray electrical fields , test your tank water from a sample away from any pumps light etc.

Take a sample from the tank using a cup and measure far away from any source of electrical fields.

[loudell]

Sounds like the meter is working perfectly and you may have discovered something that would have been missed if you did not have a meter. If you would like to send me a sample of your tank water I would be happy to check it...Lou Dell/AMI

[Randy Holmes-Farley]

When you made my salinity standard, what exactly did you do to make it?

[boxfishpooalot]

If your refractometer (calibrated with pinpoint 53 solution at 35 ppt) is good, I would trust that measurment.

Ok, good to know. But i got this meter and want to know my salinity via Pinpoint conductivity.

The monitor is prone to stray electrical fields , test your tank water from a sample away from any pumps light etc.
Really? Ill have to try this. Maybee ill do it on the balcony.

Sounds like the meter is working perfectly and you may have discovered something that would have been missed if you did not have a meter. If you would like to send me a sample of your tank water I would be happy to check it...Lou Dell/AMI
Yes that would make me really happy. What address? How much water do you need?

When you made my salinity standard, what exactly did you do to make it?

Fill a 2 liter coke bottle to the rim with ro water(no di). Dump that into a big stainless steel bowl. Add 3 tbls of ro water to that, and add 1 level scoop of 1/4 cup iodized salt. Mix it up for about 5 minutes. The solution remains foggy, i dont know why. Tested it in the metal bowl and it read 45ms/cm . Perhaps my measures are off or my salt is the wrong kind? Maybee the US measures are very different than Canadian?

The other stuff i had left over from a previous cali check i made for the refractomer, IIRC measured 45ms/cm also.... I thought they should be different?

Box

[Randy Holmes-Farley]

How did you measure that 1/4 cup? If it was by eye in a full 1 cup, it may be substantially off. The refractometer salt standard is not very different, FWIW.

I can't really say what to go with, or what might be wrong at this point.

[boxfishpooalot]

How did you measure that 1/4 cup? If it was by eye in a full 1 cup, it may be substantially off. The refractometer salt standard is not very different, FWIW

I used a straw to wipe off excess salt. Is this an bad way to do it?
I really want to get a pharmacist to do this... Although it does not seem hard to do.

Why does the salt cali soultion remain foggy even after a month? Does this hint to any problems with the salt i used?

[Randy Holmes-Farley]

There will be a little insoluble material in commercial salts.

So the solution of mine that you made reads 45 mS/cm and the tank reads 38 mS/cm? What if you let tank temperature water cool to room temperature (or whatever temp you used for the salt and Pinpoint standard?

IME, the detected conductivity of the Pinpoint rises a few mS/cm as the temperature drops. I'm not sure how cold you are up there now.

[boxfishpooalot]

So the solution of mine that you made reads 45 mS/cm and the tank reads 38 mS/cm? What if you let tank temperature water cool to room temperature (or whatever temp you used for the salt and Pinpoint standard?

Close to it. Id say 44.5ms/cm. Then i stuck it in the microwave for 10 seconds in a cup and got the temp to about 83f . Stuck the probe in and it read 48ms initially. But after a minute or so the ms started to drop again back down to 45ms/cm. Actually 45ms was yesterday when calibrated with brand new cali soultion. But now it reads 44ms/cm of your solution check. But i think its just salt residue on the probe after re-calibration.

IME, the detected conductivity of the Pinpoint rises a few mS/cm as the temperature drops. I'm not sure how cold you are up there now

Really? I thought this probe will temp compensate for temperature diffs from as low as 32f.

This winter has been so strange. Its actually +3 c right now. When we should be -30 c ! Global warming must have somthing to do with it. We got a huge snow fall 2 days ago was abou 12" of snow. Could not get to work

[Randy Holmes-Farley]

Really? I thought this probe will temp compensate for temperature diffs from as low as 32f.


It mostly does, but not perfectly. Take some warm tank water and put the probe in, then let it cool and see if it changes conductivity. Perfect correction would not, but I see it rise a few mS/cm on going from 80 deg F to 63 deg F.

My very expensive Orion meter also rises some, but not quite as much.

[boxfishpooalot]

Yes i checked its conductivity raising effect. At 85f the conductivity is 38mS/cm and at 76f its about 39mS/cm. And at 72f its reading 39.9ms/cm.

What should i take of this? You sure this raising effect is not just evaporation?

[Randy Holmes-Farley]

In my case, yes, I'm sure. Cover it with saran wrap and try again.

[boxfishpooalot]

also, would phosphates in your diy standard effect the conductivity measurment if at .25ppm Po4?

O yea and i bought a fastest nitrate kit. It reports the value as nitrate-N . Is that different than say salifert nitrate kit? Cause it reads about 95ppm. OUCH.!

[Randy Holmes-Farley]

Phosphate in seawater (even 5 ppm) has a trivially small impact on conductivity.

A kit reading in nitrate-N needs to be multiplied by 4.4 to get ppm nitrate ion. Hopefully it is inaccurate.

[boxfishpooalot]

Hope im not dragging this thread.

I tested some Limewater and it came out at 9mS/cm. It was 1 cup with 2 tsp kalk unsettled. Does it got to be 10.3mS/cm.

I have the stuff that does not heat on contact. Calcium hydroxide? Does that make a difference.

Does unsettled lime make a difference?

What does that say?

[Randy Holmes-Farley]

Limewater saturation is very temperature dependent, and that will impact the conductivity. So I do not know that you can conclude much. What temperature was it at?

[boxfishpooalot]

O im not sure it was from RO water so guessing it might be 60-70f.

I can check it again. What temp should i have it at?

[Randy Holmes-Farley]

Well, that depends. I probably wouldn't try to use it as a conductivity standard, except perhaps at 25 deg C. Then some others of us can measure the conductivity at that temp.