Best practice in calibrating the 2016 salinity probe

Guys, I think I got it. But hard to be confident at this point. And my readings are low based on the probe! Which was a previous concern based on my refractometer. Which is why I got into recalibrating to begin with. Can I remove the probe and stick it back in calibration fluid? Can it be in the air for any length of time and still be calibrated? If I remove it from the tank and place it in calibration fluid that I've acclimated to the tank it should be 35ppt. If I can do that, it would go a long way for my confidence. Guidance?

It does tend to drift a bit if it's been out of the water more than a day before calibration. Usually not more than 0.5 port, but it does impact it to a degree.

You might be an engineer if...You have no life and can prove it mathematically.

I left my TEmp Control setting at zero. Is that correct?

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Originally Posted by RussC

I left my TEmp Control setting at zero. Is that correct?

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No. You want roughly 2.2. The actual amount may vary slightly in the range of 1.9 to 2.4 depending on the type of salt you use if you keep it at 35ppt. It shouldn't make a difference on the reading after calibration if it was done between 76 and 78F and won't make a huge difference even up to 80 (it may change your reading like 0.2 ppt). The way to determine the exact value is to watch how to cond value reacts to changes in tank temp. If cond rises as temp rises, you need to increase the number 0.1 and if cond falls as temp rises, you need to decrease by 0.1. Most tanks will fall at 2.2 though.

You might be an engineer if...You have no life and can prove it mathematically.

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Originally Posted by zombie

No. You want roughly 2.2. The actual amount may vary slightly in the range of 1.9 to 2.4 depending on the type of salt you use if you keep it at 35ppt. It shouldn't make a difference on the reading after calibration if it was done between 76 and 78F and won't make a huge difference even up to 80 (it may change your reading like 0.2 ppt). The way to determine the exact value is to watch how to cond value reacts to changes in tank temp. If cond rises as temp rises, you need to increase the number 0.1 and if cond falls as temp rises, you need to decrease by 0.1. Most tanks will fall at 2.2 though.

You might be an engineer if...You have no life and can prove it mathematically.

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Can compensation done after calibration? If possible, where do I do this in Apex Fusion? Is it at Inputs>PH probe>pH Probe Configuration>Advance?

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Originally Posted by 2mk

Can compensation done after calibration? If possible, where do I do this in Apex Fusion? Is it at Inputs>PH probe>pH Probe Configuration>Advance?

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Yes and because you have the 2016 model, yes to the second question.

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Originally Posted by iamchadster

Yes and because you have the 2016 model, yes to the second question.

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Somehow there seem to be no place to put compassion value? Is it because it was not originally calibrated manually?

No, are you in the inputs screen? In the inputs screen under the Type heading find "Base_Cond". Click into that and select the advanced tab to find the compensation factor.

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Originally Posted by iamchadster

No, are you in the inputs screen? In the inputs screen under the Type heading find "Base_Cond". Click into that and select the advanced tab to find the compensation factor.

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Thanks. I was at the wrong screen. Went to the correct screen you told me, adjusted TC to 2.2, and readings have less swings, but it took the ppt readings higher. Have now adjusted TC to 1.1 and it came a bit down but still higher ppt than when TC was 0.0. Will obsere and see what happens over the next few hours.

Does the probe needs to be re-calibrated if I decide to take TC back to 0.0? Salt reading was a lot stabler before.

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Originally Posted by 2mk

Thanks. I was at the wrong screen. Went to the correct screen you told me, adjusted TC to 2.2, and readings have less swings, but it took the ppt readings higher. Have now adjusted TC to 1.1 and it came a bit down but still higher ppt than when TC was 0.0. Will obsere and see what happens over the next few hours.

Does the probe needs to be re-calibrated if I decide to take TC back to 0.0? Salt reading was a lot stabler before.

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Use a TC that is stable not what gives you the value you want. If your tank temp is close to 77F, the error will be minimal and recalibration is not necessary. If you keep your tank at 79 or above you might consider recalibrating.

You might be an engineer if...You have no life and can prove it mathematically.

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Originally Posted by zombie

Use a TC that is stable not what gives you the value you want. If your tank temp is close to 77F, the error will be minimal and recalibration is not necessary. If you keep your tank at 79 or above you might consider recalibrating.

You might be an engineer if...You have no life and can prove it mathematically.

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Calibrated the probe for a week now and it seems stable but creeping up. Surprisingly, readings dropped below 37 after my water change on saturday night, has been increasing since.

I was just wondering if TC can fix the slowly rising problem. It turns out it doesn't. I have now set TC back to 0.0 and see waht will happen. Hopefully I don't have to recalibrate. Please see chart below. Attachment 8058
I recalibrat

The slowly rising thing is either new probe break in (took 4 days for mine) or bubble accumulation (I use a magnetic probe rack at a 10 degree angle and in a section with minimal bubbles to prevent this). Temp compensation is solely used to smooth changes due to temp. I consider stable for that oscillations of no more than +- 0.2 ppt per degree F change.

You might be an engineer if...You have no life and can prove it mathematically.

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Originally Posted by zombie

The slowly rising thing is either new probe break in (took 4 days for mine) or bubble accumulation (I use a magnetic probe rack at a 10 degree angle and in a section with minimal bubbles to prevent this). Temp compensation is solely used to smooth changes due to temp. I consider stable for that oscillations of no more than +- 0.2 ppt per degree F change.

You might be an engineer if...You have no life and can prove it mathematically.

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Thanks. I will recalibrate it again keeping all of the points you mentioned concerning Temperature, Temp Comp, interferecnes, and etc. So far the fluctuations are still higher that +-0.2 ppt per F degree.

I'm not sure I'm getting this right. after washing the probe thoroughly in RO, I let it sit out for a day, then heated up a cup of water to about 77°+/-. I let the salinity packet (53.0 µS) soak in the water for about 20 minutes, then proceeded to do the calibration. Unfortunately, even after 24 hours, the automatic calibration would not consider the probe dry. we even used a hand blower for my PC to dry it more. Didn't work. The automatic calibration won't accept the probe. We did it on manual, but I'm guessing it didn't work, as my salt levels are chaotic. Overall, the tank is about 34 with the refractometer, but the Apex probe is showing up at 24.7 at the moment. any ideas?

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Originally Posted by boneless3vil

I'm not sure I'm getting this right. after washing the probe thoroughly in RO, I let it sit out for a day, then heated up a cup of water to about 77°+/-. I let the salinity packet (53.0 µS) soak in the water for about 20 minutes, then proceeded to do the calibration. Unfortunately, even after 24 hours, the automatic calibration would not consider the probe dry. we even used a hand blower for my PC to dry it more. Didn't work. The automatic calibration won't accept the probe. We did it on manual, but I'm guessing it didn't work, as my salt levels are chaotic. Overall, the tank is about 34 with the refractometer, but the Apex probe is showing up at 24.7 at the moment. any ideas?

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Try to heat the tank up to 77f if you use a chiller and keep the temp below 77f. Dunk the calibration liquid pack in the tank for an hour or so. Also note that I became aware that there is a break in period for these probes. Just let it sit in the tank and recalibrate after a couple of weeks.

Also note that there is temperature correction involved for calibration if you water is not at 77f. Technically, if your temp is at 77f, there is no need to use temp correction.

make sure your temp is stable enough, meaning no clogged chillers can cause problems in calibration. I had this as my major problem. Once the clogging is fixed, calibration is as easy as it said here by everyone else.

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Originally Posted by 2mk

Also note that there is temperature correction involved for calibration if you water is not at 77f. Technically, if your temp is at 77f, there is no need to use temp correction.

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I will rephrase so this doesn't get misinterpreted. At 77F the salinity measurement before and after temperature compensation is equal because it's the basepoint used to determine how much ppt to add or subtract from the raw measurement. If you calibrate at 77F then if you discover later that you need to tweak the temperature compensation value so that cond doesn't oscillate with temp, you don't have to recalibrate to get an accurate reading. Temperature compensation is still a must regardless of the calibration temperature because nearly all tanks do not have a target temp of 77F and heaters and chillers will vary the temp even if the target is 77F.

You might be an engineer if...You have no life and can prove it mathematically.

I have probably went through 6 calibration packets already. I followed the steps to the T and the probe reads 34.7 PPT in the solution when I am done. But once I put it in my tank, it reads 27.5 ppt when it is 35 ppt. My water temp is 81 and I calibrated at 77 with the temperature probe at 77 as well. Temperature compensation was on 2.2 when I calibrated. I could see that as the temperature started rising when I put both probes back into my tank, that the salinity was going down in an inverse relationship. I changed temperature compensation to 0 and now it reads 34.3 which is at least closer to what it is. I use a Milwaukee electronic salinity checker and a handheld refractometer to verify that my salinity is indeed 1.026(35ppt).

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Originally Posted by 2mk

Calibrated the probe for a week now and it seems stable but creeping up. Surprisingly, readings dropped below 37 after my water change on saturday night, has been increasing since.

I was just wondering if TC can fix the slowly rising problem. It turns out it doesn't. I have now set TC back to 0.0 and see waht will happen. Hopefully I don't have to recalibrate. Please see chart below. Attachment 8058
I recalibrat

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If you condense your graph down to a day the changes wouldn't look so drastic. How big is your tank and how often is your ATO coming on? The changes you are seeing are less than 1 PPT in most cases which to me seems pretty good.

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Originally Posted by ShadowR55

I have probably went through 6 calibration packets already. I followed the steps to the T and the probe reads 34.7 PPT in the solution when I am done. But once I put it in my tank, it reads 27.5 ppt when it is 35 ppt. My water temp is 81 and I calibrated at 77 with the temperature probe at 77 as well. Temperature compensation was on 2.2 when I calibrated. I could see that as the temperature started rising when I put both probes back into my tank, that the salinity was going down in an inverse relationship. I changed temperature compensation to 0 and now it reads 34.3 which is at least closer to what it is. I use a Milwaukee electronic salinity checker and a handheld refractometer to verify that my salinity is indeed 1.026(35ppt).

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I wish I sold calibration fluid. :) How long are allowing the probe to settle in the tank. You certainly shouldn't have to calibrate 6 times and I would suggest keeping the comp at 2.2 as long as you have your temp probe set up correctly to work with your cond probe. IE, plugged into a pm2 or the Apex base unit on the 2016 model. I didn't look to see which Apex you had as I was too lazy to open another window.

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Originally Posted by iamchadster

I wish I sold calibration fluid. :) How long are allowing the probe to settle in the tank. You certainly shouldn't have to calibrate 6 times and I would suggest keeping the comp at 2.2 as long as you have your temp probe set up correctly to work with your cond probe. IE, plugged into a pm2 or the Apex base unit on the 2016 model. I didn't look to see which Apex you had as I was too lazy to open another window.

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I have a 2016 unit, it’s a unit I installed in December and I have never had an accurate salinity reading. I think my probe might be defective. I left it for 5 minutes and I let everything settle, the first number settled at 88 and the second settled at 535. I tried EVERYTHING, I don’t know what else to do, pretty frustrating.

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Originally Posted by ShadowR55

I have a 2016 unit, it’s a unit I installed in December and I have never had an accurate salinity reading. I think my probe might be defective. I left it for 5 minutes and I let everything settle, the first number settled at 88 and the second settled at 535. I tried EVERYTHING, I don’t know what else to do, pretty frustrating.

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One thing that can help is to "reset" the port. You unplug the probe and run a calibration without it. Then you can try the calibration again with it plugged in.

You might be an engineer if...You have no life and can prove it mathematically.

Finally got it calibrated correctly. I changed the temp compensation back to 2.2 and then used my Milwaukee digital refractometer(calibrated it first) to make sure my tank was at 35ppt and then I did a manual calibration by selecting the same 53ms under the calibration fluid drop down and putting the probe back in my tank. I happened upon someone posting on reef2reef about how calibration fluids are pointless and to calibrate it in the tank. He was so right, I wish I didn’t already buy 6 more packets of fluid...

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Originally Posted by ShadowR55

I happened upon someone posting on reef2reef about how calibration fluids are pointless and to calibrate it in the tank. He was so right, I wish I didn’t already buy 6 more packets of fluid...

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I might have to try that. I've done everything everyone's told me and still, my salinity shows 24.3, when it's 34. It's so far off LOL

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Originally Posted by boneless3vil

I might have to try that. I've done everything everyone's told me and still, my salinity shows 24.3, when it's 34. It's so far off LOL

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That big of a difference (assuming your packet matches tank temp) would indicate that you likely need to "reset" the probe. Run a calibration with it unplugged, then try the proper calibration procedure. The only reason the "calibrating in the tank" works so well is that it eliminates the most common mistakes in calibration, but it's by no means accurate. Even with a well calibrated refractometer the best you can do is be within 0.5-1 ppt of actual. Proper calibration with a packet can get you within 0.1.

You might be an engineer if...You have no life and can prove it mathematically.

I too bad problems when I first got my apex 2016. After losing some of the same questions y'all are posting we all came to the same conclusions zombie mentioned above.
1 let the probe soak for a week (mine took about 3 before it would calibrate correctly)
2 deliberating monthly is best
3 always double check with a refractometer occasionally. I do it weekly because it still wonders occasionally.
@zombie your help on all our questions is greatly appreciated