refractometer cal

[tommygun]

Hello I need some advice on calibrating a Refractometer. I have had and used a Refractometer for a long time I found them to be easy to use accurate or at the very least consistent if nothing else. I always used water as a baseline either RO or distilled, to be blunt I never had to change the reference and that concerned me because I like to keep on the high side for my mini reef 1.024-1.026. I misplaced my first Refractometer so I purchased two new ones and one was to be a backup and as luck would have it I found my original one a day after I placed my order. Finally I wanted to address the one little issue that has been on my mind since I first purchased it and that was am I reading accurately?

So I purchased a calibration fluid from BR. The standard on the fluid is 35 PPT but when tested it I read 38 PPT sounds simple right just turn it down. Not quite when I did my water baseline I was on the minus side, and my salt level now read 1.021. So I freaked out so before I did some water changes to raise my salt level I used the new and unused Refractometer and my salt level read 1.024 so I ran the cal fluid on that meter and the results came out 38 PPT so I did the same thing with my backup and it read 38PPT the same amount as my original one and all had a water baselines in the minus side.

I emailed BR$ to find out more about it and the advice was less than satisfactory the manager told me not to worry about it that the 35% PPT is a standard and that is closest to what reef keepers use ( I got that). His advice further bothered me and told me that was RO and distilled water both make a poor standard that I should go with the calibration fluid or try another calibration fluid brand if I have any doubts. He never addressed how can three Refractometers could be off by the same amount two of them brand new and unused. The manager further dismissed it by saying it's just a reference anyways. I'm leaning towards just using Distilled as a baseline and ignoring the cal standard. What are the chances someone has three Refractometer s Any advice and is anybody else having this issue? I'm not knocking anyone down I like BR$.

I'm having issues logging in every time I need to log in I have to submit a password reset so it may take a while for me to respond.

 

[ccCapt]

If you are saying all 3 read 38ppt with the calibration fluid, I don't see a problem. Just lower the adjustment screw so it reads 35ppt. It's normal that distilled water would then read less than 0. I would go with the calibration fluid as the proper setting for them.

 

[reefrunner69]

This is a pretty interesting read for you. http://reefkeeping.com/issues/2006-12/rhf/index.php

Are the refractometerrs ATC? If no was the appropriate temp observed? If they are did you leave the sample on the refractometer for 30 seconds to allow the temp compensation?

 

[Schism]

Using distilled and ro/di is a less accurate way pf calibrating because you are standardizing the refractometer to read 1.000 and thats only if its a pure same. Well of its off just a tiny amount at 1.000 then its way off at 1.026.

If you calibrate at 1.026 or 35ppt with the calibrating solution that is standardized then you will get a more accurate reading, ive used it for years and never had a problem. I think you need to adjust your screw to the calibration fluid. If originally calibrated with distilled then that is why you see the .003 difference.

Hope that makes sense.

 

[tommygun]

You don't work for BRS? Just kidding. I just having a hard time believing it's that simple but it could and plus I forgot I did a hydrometer test that confirmed that I was around 1.024. I'm not saying a hydrometer is accurate by any means. The cal fluid could be correct and right on the money but pure water having a specific gravity of - 0 by about 3-4 PPT is hard to trust. All my meters are ATC type as most are now days I waited the recommended time and then waited some more time. I could trust the fluid to be 35 PPT but if it's off by 3 PPT I could be actually be at 1.028-1.029 or higher SG if it's wrong and reading 1.025-1.026 on the meter
if that makes any sense.

I have four sources of water in which I used to get my zero baseline distilled my RO/DI system with 0 TDS tap water and water I distilled using as method recommended by a forum member in another topic by steaming it off a cold plate.

Just for the record I have a JBJ c-scope, a precession and a Milwaukee all ATC meters. I pretty sure I need to buy a cal fluid from another source to be sure.

I really appreciate you taking the time to respond

Thank you

 

[tommygun]

thank you reef runner 69

My refractometers are ATC type I waited the recommend 45 seconds and then waited some more I have waited even less with the same results 38 PPT.

Thank you

 

[tommygun]

Schism thank you

Good advice I originally didn't calibrate my old Refractometer until after I purchased the Cal fluid I didn't use DI and established 1.000 and then discovered I was off by 3 PPT when I did the cal fluid. I actually did the cal fluid first freaked out and then asked my LFS for advice it was them that told me about using DI. The cal fluid could be correct and all three meters were off the used one and 2 new ones.

Just to clarify I didn't establish (tweak) 1.000 with DI first and then did the cal fluid. I calibrated my Refractometer only with the cal fluid and I left the other two alone. They read 1.000 from the factory I never tweaked them to get that reading. The only thing I can come up with is all three Refractometer s all three from different brands may have used the same standard of using DI to establish 1.000.


I think what I need to do is use another brand of cal fluid just to be sure.

Thank you

 

[Schism]

Good advice I originally didn't calibrate my old Refractometer until after I purchased the Cal fluid I didn't use DI and established 1.000 and then discovered I was off by 3 PPT when I did the cal fluid. I actually did the cal fluid first freaked out and then asked my LFS for advice it was them that told me about using DI. The cal fluid could be correct and all three meters were off the used one and 2 new ones.

Just to clarify I didn't establish (tweak) 1.000 with DI first and then did the cal fluid. I calibrated my Refractometer only with the cal fluid and I left the other two alone. They read 1.000 from the factory I never tweaked them to get that reading. The only thing I can come up with is all three Refractometer s all three from different brands may have used the same standard of using DI to establish 1.000.


I think what I need to do is use another brand of cal fluid just to be sure.

Thank you

Try marine depot. Thats where i got mine, pinpoint salinity calibration fluid. Never had a problem with it. Also make sure your shaking the bottle up fairly well too

 

[tommygun]

Update I purchased a bottle of pinpoint salinity monitor cal fluid. it verified that the aqua craft products was accurate both solutions read exactly the same 35 PPT on the Refractometer I previously calibrated and 38 PPT on the other two I also tested my brothers which also read 38 PPT. The only thing I can come up with is all the manufactures must use DI to calibrate from the factory the odd thing is my brother just received his from BRS. The pinpoint solution is slightly more expensive and a little harder to use and wasteful because you need a pipette to draw a sample where as the aqua craft has its own dropper. I guess it's time to raise my salinity?

 

[Schism]

Update I purchased a bottle of pinpoint salinity monitor cal fluid. it verified that the aqua craft products was accurate both solutions read exactly the same 35 PPT on the Refractometer I previously calibrated and 38 PPT on the other two I also tested my brothers which also read 38 PPT. The only thing I can come up with is all the manufactures must use DI to calibrate from the factory the odd thing is my brother just received his from BRS. The pinpoint solution is slightly more expensive and a little harder to use and wasteful because you need a pipette to draw a sample where as the aqua craft has its own dropper. I guess it's time to raise my salinity?

Glad you got it all figured out. You dont need to calibrate that often. One bottle of calibration fluid should last years. I use a pipette to get a few drops and thats it. Im sure you could find a dropper cap to fit also.