tibbsy07 Posted June 12, 2014 Share Posted June 12, 2014 I'm not one to pick apart someones product without trying it, but this seems a bit misleading I agree. The refractometer is probably great, but this claim seems to be a bit of a stretch. My place is always at 72 degrees. Not 77. There would have to be a compensation based on their calibration and algorithm. Quote Link to comment
jedimasterben Posted June 12, 2014 Share Posted June 12, 2014 I agree. The refractometer is probably great, but this claim seems to be a bit of a stretch. My place is always at 72 degrees. Not 77. There would have to be a compensation based on their calibration and algorithm. Tanks are almost never kept at ambient temperature. I'm not one to pick apart someones product without trying it, but this seems a bit misleading I would, but only if crazy claims are made lol A muy importante article on salinity and refractometers: http://reefkeeping.com/issues/2006-12/rhf/ 1 Quote Link to comment
tibbsy07 Posted June 12, 2014 Share Posted June 12, 2014 Tanks are almost never kept at ambient temperature. I would, but only if crazy claims are made lol Right but the refractometers are, and the few drops of water used lose their temperature very quickly as soon as they hit the refrac glass. My point is that all refracs have a calculation for optimal temperature and rarely do people hit that exact temp, meaning their results are off. Their tanks tend to be fine. I think stability is more the issue with salt and water. 1 Quote Link to comment
metrokat Posted June 12, 2014 Author Share Posted June 12, 2014 I suppose it is possible that Red Sea would put out a product and give people utterly wrong instructions on how to calibrate it. I agree. The refractometer is probably great, but this claim seems to be a bit of a stretch. My place is always at 72 degrees. Not 77. There would have to be a compensation based on their calibration and algorithm.Can I move into your place because the brother insists on keeping it 75+ degrees here. I swear I need a portable air conditioner around my neck. Quote Link to comment
Veng Posted June 12, 2014 Share Posted June 12, 2014 A refractometer should read 35 ppt when testing with 35 ppt calibration fluid. If it doesn't it's not calibrated properly or the calibration fluid is bad, period. Calibrating with distilled water is simply wrong and will lead to errors. I would NEVER trust a refractometer that was calibrated w/ RODI over one that was calibrated with 35 ppt fluid. I'm a big fan of Red Sea, but this is simply wrong. 1 Quote Link to comment
tibbsy07 Posted June 12, 2014 Share Posted June 12, 2014 If the refractometer is supposed to be calibrated with di water, cool. Do that. But i think that because of the way the red sea refrac algorithm is, it won't read the 35ppt fluid the way the other refractometer will. They use different methods and the 35ppt fluid is designed for the standard refrac. Quote Link to comment
jbb Posted June 12, 2014 Share Posted June 12, 2014 One of the reasons I like my Milwaukee so much is that it displays the sample temp. Directions say to let it sit for 45 seconds to let the temp level out before reading the sample. So far the temp has stopped moving around the 30 second mark. I have tried calibrating with 35ppt solution - dead on , Tried again with my RO/DI - zero. Those results made me feel pretty good about trusting it. Oh, and I'm with tibbs , my house stays very cool . I leave the stat on 68* 3 Quote Link to comment
jedimasterben Posted June 12, 2014 Share Posted June 12, 2014 A refractometer should read 35 ppt when testing with 35 ppt calibration fluid. If it doesn't it's not calibrated properly or the calibration fluid is bad, period. Calibrating with distilled water is simply wrong and will lead to errors. I would NEVER trust a refractometer that was calibrated w/ RODI over one that was calibrated with 35 ppt fluid. I'm a big fan of Red Sea, but this is simply wrong. Precisely - what we want to measure is the refractive index - as long as the target you want is a known number and you have a calibration solution that matches that refractive index, that is what matters, per RHF in the article I linked to. If the refractometer is supposed to be calibrated with di water, cool. Do that. But i think that because of the way the red sea refrac algorithm is, it won't read the 35ppt fluid the way the other refractometer will. They use different methods and the 35ppt fluid is designed for the standard refrac. As long as the refractive index of the calibration solution is the refractive index you are hoping to measure, then they will be identical, as that is the only measurement you are taking. For example, to measure the salinity of seawater at 35 ppt, calibrate a refractometer using a standard with the same refractive index, and the slope miscalibration error disappears when measuring seawater samples near that salinity (Figure 14). - RHF Quote Link to comment
metrokat Posted June 12, 2014 Author Share Posted June 12, 2014 I realize that , but one statement says it isn't needed "No need for seawater or temperature compensation factors", but then they go on to say that it is included "for accurate measurement at standard ambient temperature". so is it needed or no ? I understood these statements to mean that the user does not need to warm or cool the water to be tested because the instrument comes with ATC. Yes, so does my other refractometer. However since it is set to measure the refractive index of brine and not seawater, the temperatures it compensates for could be different than what Red Sea compensates for. Quote Link to comment
Veng Posted June 12, 2014 Share Posted June 12, 2014 If the refractometer is supposed to be calibrated with di water, cool. Do that. But i think that because of the way the red sea refrac algorithm is, it won't read the 35ppt fluid the way the other refractometer will. They use different methods and the 35ppt fluid is designed for the standard refrac. Refraction is simply physics. The refraction of a 35 ppt sample IS 1.33940. If the refractometer's scale isn't set to a refractive index 1.33940 = 35ppt then the refractometer is wrong. 5 ppt error is exactly the kind of error you expect when you calibrate with RODI water, and it's exactly why you shouldn't. 1 Quote Link to comment
jedimasterben Posted June 12, 2014 Share Posted June 12, 2014 I still vote #vengforpresident Quote Link to comment
metrokat Posted June 12, 2014 Author Share Posted June 12, 2014 A refractometer should read 35 ppt when testing with 35 ppt calibration fluid. If it doesn't it's not calibrated properly or the calibration fluid is bad, period. Calibrating with distilled water is simply wrong and will lead to errors. I would NEVER trust a refractometer that was calibrated w/ RODI over one that was calibrated with 35 ppt fluid. I'm a big fan of Red Sea, but this is simply wrong. But you've never used a refractometer designed, specifically, for seawater either. The refractometer used to make beer and foods is the same one we all currently use in the hobby. How come we all trust that? Quote Link to comment
jedimasterben Posted June 12, 2014 Share Posted June 12, 2014 But you've never used a refractometer designed, specifically, for seawater either. The refractometer used to make beer and foods is the same one we all currently use in the hobby. How come we all trust that? Physics doesn't not apply anymore because it's designed for use with 'seawater'. Seawater has a refractive index and that is what you are measuring. As long as you know what measurement you are looking for and have a calibration solution that matches it closely, then any refractometer will work as it will read the same exact point on the scale, regardless of what number it assigns to it. Quote Link to comment
Veng Posted June 12, 2014 Share Posted June 12, 2014 But you've never used a refractometer designed, specifically, for seawater either. The refractometer used to make beer and foods is the same one we all currently use in the hobby. How come we all trust that? Because physics doesn't change based on what you're measuring. I don't have to buy a different scale to weigh barely when I make beer than one when I weigh salt to make salt water, either. 1 Quote Link to comment
tibbsy07 Posted June 12, 2014 Share Posted June 12, 2014 Refraction is simply physics. The refraction of a 35 ppt sample IS 1.33940. If the refractometer's scale isn't set to a refractive index 1.33940 = 35ppt then the refractometer is wrong. 5 ppt error is exactly the kind of error you expect when you calibrate with RODI water, and it's exactly why you shouldn't.Right, I get the physics. I guess I'm thinking they changed something about the prism design or something to read differently? Considering we don't use natural sea water in our tanks, it seems a bit odd to need to use the refrac to do that, but... in addition, it means that the salt makers are using the norm refractometers to QC their salt. That means it would be better to use a normal refrac to measure the salinity of the water you make with their salt. Not use a refractometer that measures sea water that you aren't using. Quote Link to comment
MikeTR Posted June 12, 2014 Share Posted June 12, 2014 One of the reasons I like my Milwaukee so much is that it displays the sample temp. Directions say to let it sit for 45 seconds to let the temp level out before reading the sample. So far the temp has stopped moving around the 30 second mark. I have tried calibrating with 35ppt solution - dead on , Tried again with my RO/DI - zero. Those results made me feel pretty good about trusting it. Oh, and I'm with tibbs , my house stays very cool . I leave the stat on 68* and if you catch it on a BRS black friday it's in the $70ish range.. which is only a couple bucks more than a quality refrac. 2 Quote Link to comment
metrokat Posted June 12, 2014 Author Share Posted June 12, 2014 Oh, and I'm with tibbs , my house stays very cool . I leave the stat on 68* Looks like you're inviting me ovah. 1 Quote Link to comment
jbb Posted June 12, 2014 Share Posted June 12, 2014 Looks like you're inviting me ovah. I'll think about it 1 Quote Link to comment
metrokat Posted June 12, 2014 Author Share Posted June 12, 2014 BTW I agree with the accuracy of digital refractometers. This discussion pertains to handheld refractometers. I would for sure be interested to read the salinity via one of these and compare to red sea. Quote Link to comment
jbb Posted June 12, 2014 Share Posted June 12, 2014 BTW I agree with the accuracy of digital refractometers. This discussion pertains to handheld refractometers. I would for sure be interested to read the salinity via one of these and compare to red sea. I guess that means you need to come ovah Quote Link to comment
NanoTopia Posted June 12, 2014 Share Posted June 12, 2014 Most calibration fluids are brine and calibrated at 77F degrees. The RedSea refractometer is calibrated with sea water at NSW levels and at a temperature of 25 degrees celsius (77F). So it might make sense that when you calibrate the RedSea refractometer you get the wrong result. Perhaps this is why they are asking for a RO water calibration. Even with such, when you put a brine calibration fluid on the refractometer to test it will not match up. Mix exactly 38grams of a balanced sea salt that mixes up at NSW levels (RedSea Blue Bucket for example), with exactly 1L of RO water. Bring the temperature up to 20-25c and test. You will have correct 35 ppt (SG 1.026). Save in a sealed bottle and you have a new calibration fluid. Just remember temperature affects readings so if your RedSea refractometer is cold or at room temperature, say ~20c, it will quickly cool down the water sample and again, you will get incorrect readings. Quote Link to comment
metrokat Posted June 12, 2014 Author Share Posted June 12, 2014 11:35am Fuge off DT on 79.1 8.18 Most calibration fluids are brine and calibrated at 77F degrees. The RedSea refractometer is calibrated with sea water at NSW levels and at a temperature of 25 degrees celsius (77F). So it might make sense that when you calibrate the RedSea refractometer you get the wrong result. Perhaps this is why they are asking for a RO water calibration. Even with such, when you put a brine calibration fluid on the refractometer to test it will not match up. Mix exactly 38grams of a balanced sea salt that mixes up at NSW levels (RedSea Blue Bucket for example), with exactly 1L of RO water. Bring the temperature up to 20-25c and test. You will have correct 35 ppt (SG 1.026). Save in a sealed bottle and you have a new calibration fluid. Just remember temperature affects readings so if your RedSea refractometer is cold or at room temperature, say ~20c, it will quickly cool down the water sample and again, you will get incorrect readings. I guess that means you need to come ovah I need to come ovah 1 Quote Link to comment
nicholc2 Posted June 12, 2014 Share Posted June 12, 2014 I have the D-D Refractometer which the instructions and description sound exactly like the RedSea. I always calibrate with DI and get consistent results. Using 35ppt solution never worked for me since it's not calibrated for that, but natural sea water. I would go with their instructions and only use DI to calibrate it. http://www.theaquariumsolution.com/seawater-refractometerAs far as the ATC, that mainly is for the refractometer itself. If you put any test water onto the unit, it will only take a matter of a few seconds for that little amount of water to adjust to the temperature of the refractometer. I have seen this first hand as I can take water from my tank and look immediately or even in a couple minutes and the reading doesn't change. The same holds true to the unheated DI I use for calibration. On a side note, the D-D holds it's calibration REALLY well. After the initial adjustments, I haven't had to make any since other than maybe a micro millimeter move or less just because I'm anal. 1 Quote Link to comment
metrokat Posted June 12, 2014 Author Share Posted June 12, 2014 So it sounds like Red Sea and D-D refractometers are different from the usual ones we all have. I wonder why there is an automatic disbelief of the accuracy of these instruments because of the calibration with DI? It's never to late to learn something new. 1 Quote Link to comment
NanoTopia Posted June 12, 2014 Share Posted June 12, 2014 Calibrate with DI and cross check with a proper salinity standard. Cant go wrong. 3 Quote Link to comment
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