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Innovative Marine Aquariums

Help with Refractometer


Jwilken02

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I just purchased a new refractometer after losing faith in my last one, it was showing weird numbers with the calibration fluid, RODI water, and then tested it on lfs tanks and it would change sporadically between all of them. Well now I have a new one from the LFS, we even tested it on several tanks with different salinity to make sure it worked. Well now I have finally got my salinity reading back to 1.024 (still need to get it to .025) and was going to recalibrate it with fluid 35 ppt, which read 40 on the refractometer so I got nervous and tested it on my RODI which read .001. Should I trust the reading? Should I calibrate back to 35ppt with the fluid? My water would be way off then. Everything seems pretty good right now, still recovering from my salinity dropping to less than 1.020. I am about to drop the this whole refractometer for the old school swing arm that I have always used till this build if I can't figure it out. Thank you for any help

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What do the instructions say for calibration?

 

Follow them to calibrate. Also if the calibration fluid is old it might be off from what it should be.

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a brand would help as well, some hold calibration better than others, some need to be calibrated everytime they are used. i calibrate with pure RO water and calibration fluid, i use the fluid first then check with RO water. oddly enough my meter from national industrial supply only lost 1 PPT in about 7-8 months, but like i said every meter is different.

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It says ATC on it, this is just driving me nuts how much more difficult it is to trust over a swing arm. I know the swing arm isn't as precise but I mean if you have to recalibrate daily with 2 different test and then test your water and everything needs to be at the same temp, by that point I am already thinking something is wrong

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It says ATC on it, this is just driving me nuts how much more difficult it is to trust over a swing arm. I know the swing arm isn't as precise but I mean if you have to recalibrate daily with 2 different test and then test your water and everything needs to be at the same temp, by that point I am already thinking something is wrong

ATC stands for Auto Temp compensation, so the temp really doesnt matter a whole lot, also the amount of water used equalizes quickly anyway. is there any sort of brand info?

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The case says National Industry Supply, not real sure how old the calibration fluid is, got it from another reefer. It's just weird that when I test the calibration fluid it seems pretty far off, test RODI it's just barely off, and when I test my saltwater it seems to be exactly where it measured a few days ago after my water change

As an instrument rated pilot I can't stand losing faith in an instrument. I just find it hard to believe if I recalibrate from 40 ppt back down to 35 ppt I will be looking at a salinity of about 1.020 if I were to guess, after the first issue last week I added a bunch of salt to get it back up so I can not fathom my salinity being low, I was freaking out that I was going to end up with hyper salinity

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The case says National Industry Supply, not real sure how old the calibration fluid is, got it from another reefer. It's just weird that when I test the calibration fluid it seems pretty far off, test RODI it's just barely off, and when I test my saltwater it seems to be exactly where it measured a few days ago after my water change

As an instrument rated pilot I can't stand losing faith in an instrument. I just find it hard to believe if I recalibrate from 40 ppt back down to 35 ppt I will be looking at a salinity of about 1.020 if I were to guess, after the first issue last week I added a bunch of salt to get it back up so I can not fathom my salinity being low, I was freaking out that I was going to end up with hyper salinity

make sure its not one designed to measure something else, they make a lot of different meters. i wouldnt trust that solution just because you dont know its history, so for now id trust the RO water before the fluid as long as the TDS is zero. also try to remember that a refractometer is by no means as accurate as aircraft instruments, as long as its within a couple points up or down its safe. trust i feel your pain about having inaccurate instruments, my father was an aircraft mechanic and by proxy spent many youthful hours watching them being repaired. look for consistency, like is it always 2 PPT high or does it vary all the time.

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I check my RODI real quick, yesterday morning it read .001

I really appreciate the help by the way, can't thank you enough. I am a student and this has been stressing no me out all day throughout my classes this week

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So my RODI measured in again around the .001-.002 (hard to decipher it) and yesterday afternoon I added a tad bit of salt and am now reading in between 1.024-1.025 it looks like.

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I've had some struggles with refractometers as well, many people rave about them, but I've found them to not be as trustworthy as I like them to be. I had an ATC Refractometer, but it was very affected by it's temperature.

 

My advise would be to not wholeheartedly trust in how your meter reads, when things don't seem right in your tank.

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you can take it to your lfs to see if it compares to these unit, sometime they can help you calibrate it. dont calibrate at 0, always should calibrate at 35 (1.026)

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you can take it to your lfs to see if it compares to these unit, sometime they can help you calibrate it. dont calibrate at 0, always should calibrate at 35 (1.026)

Disagree.

 

Always calibrate using manufacturer methods. For some that's 35ppt for others its use rodi water.

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Disagree.

 

Always calibrate using manufacturer methods. For some that's 35ppt for others its use rodi water.

 

OK , I understand why you would follow the manufactures directions...but i dont understand why you wouldnt calibrate at 35 ppt when thats what we measure. I think its possible the manufactures recommendations are based on using the refrag on other liquids and using RODI water would be the universal baseline.

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you can take it to your lfs to see if it compares to these unit, sometime they can help you calibrate it. dont calibrate at 0, always should calibrate at 35 (1.026)

I don't agree with this. I am almost 100% confident that my RO/DI is 1.000. I am not confident that my calibration solution is 1.026 long term as you don't know what they used to make it. It is a good check to see what the calibration solution is, but reliably RO/DI is your best calibration. Keep in mind that ATC requires you to wait for temperature to stop changing, so in reality room temp. Keep in mind that your refractometer is only going to be accurate at best to +/- 0.002 depending on the model.

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If you almost 100% sure, then your NOT sure. The water you make can be affected by worn filters etc.

BRS recommends calibrating at 35, if you Google you will find old salts doing it at 35.

If you are happy and consistent then do it the way you want.

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when we calibrate our equipemnt we are looking for and if needed correcting deviation in measurement. if the refractometer is made correctly the deviation should be consistent. if the deviation is one hash line at the RO/DI water level it should be deviated one line at all points along the scale. if its not, either the fluid is off or something is wrong with the meter. that being said, calibration fluid is, or supposed to be, a known level, the same as RO/DI water. for our refractometers, it doesnt matter if you use store bought fluid, homemade fluid, or RO/DI. as long as the value is known, it will work. i suggest using calibration fluid and RO/DI as a double check if you will.

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when we calibrate our equipemnt we are looking for and if needed correcting deviation in measurement. if the refractometer is made correctly the deviation should be consistent. if the deviation is one hash line at the RO/DI water level it should be deviated one line at all points along the scale. if its not, either the fluid is off or something is wrong with the meter. that being said, calibration fluid is, or supposed to be, a known level, the same as RO/DI water. for our refractometers, it doesnt matter if you use store bought fluid, homemade fluid, or RO/DI. as long as the value is known, it will work. i suggest using calibration fluid and RO/DI as a double check if you will.

I agree. most of us may not have lab grade refractometers and thus the deviation.

 

*less deviation if calibrated at 35 vs 0 since we are testing at 35

 

at the very least, ask another reefer or LFS to double check the salinity of your water.

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I have 2 refractometers, one from Red Sea and a generic from ebay. Red Sea one is a bit heavier and seem to have better build quality.

The biggest difference was the deviation when I calibrated at 0 and 35.

 

Red Sea calibrated at '1.026' then used DO water and read '0'; calibrated at '0' used calibration fluid read 1.026'

Generic calibrated at '1.026' then used DO water and read '-.02'; calibrated at '0' used calibration fluid read '1.028'

 

This test tells me if the refractometer is poorly made, it would be best to calibrate at1.026 (35). For better refractometers it wouldn't matter as much.

 

20160217_002120.jpg

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