steveoutlaw December 29, 2011 Share December 29, 2011 Ok, so there is all this hype about seawater vs saltwater refractometers. So, I purchase a D-D seawater refractometer to make sure everything is ok. When I compared it to my old no name refractometer......it was identical. So then I tried it on RODI water and they both read spot on zero. So either my really old refractometer is ahead of it's time or this is just a marketing scheme!! Link to comment Share on other sites More sharing options...
Incredible Corals December 29, 2011 Share December 29, 2011 Lol! Thanks for sharing your results. Link to comment Share on other sites More sharing options...
smallreef December 30, 2011 Share December 30, 2011 yeah,, i think its just a ploy from manufacturers to get people to buy a new one.. seawater and "home made" saltwater are similar enough (since you are testing the measure of salt in the water) that any refractometer that is calibrated correctly should both have the same numbers.... Link to comment Share on other sites More sharing options...
Origami December 30, 2011 Share December 30, 2011 That's good news. It's not always the case, though. There are some cheap refractometers out there that have poorly designed scales. Personally, it wouldn't matter to me if I was using my $20 EBay model or a DD model costing 4 times as much, I'd still calibrate it in the vicinity of where I intended to make a measurement rather than using RO/DI or distilled. I'd do this to minimize offset and linear measurement errors. Link to comment Share on other sites More sharing options...
Coral Hind December 30, 2011 Share December 30, 2011 I picked up a high end refractometer from a member leaving the hobby this week and I tested it to my cheap $20 Ebay one. When calibrated with R/O water my cheap one was off, instead of my tank being at 1.025 it was actually 1.021. Once calibrated with the proper solution it was accurate which shows the scale is off on the cheapo unit. Link to comment Share on other sites More sharing options...
bankyf December 30, 2011 Share December 30, 2011 I recently purchased the Milwaukee digital refractometer and I have to say it is one of the nicest pieces of test equipment I have ever purchased. I know a refractometer is already pretty easy to use, but once you use one of these you will never want to go back. It calibrates with a few drops of ro water and the press of a buttan and gives you an instant reading with a few drops of saltwater and the press of a button. No option to calibrate with calibration fluid, but it matches the calibration fluid perfectly when calibrated with ro. Not sure if it is setup for seawater or saltwater though Link to comment Share on other sites More sharing options...
RicSG December 30, 2011 Share December 30, 2011 I do not have the proper solution to calibrate my refractometer. Where can I get it locally 22192. Sorry off topic. Link to comment Share on other sites More sharing options...
Origami December 30, 2011 Share December 30, 2011 Have you tried calling BRK or F&F? Link to comment Share on other sites More sharing options...
steveoutlaw December 30, 2011 Author Share December 30, 2011 Funny thing is, the D-D directions say to use RO water and not a calibration fluid. Link to comment Share on other sites More sharing options...
RicSG December 30, 2011 Share December 30, 2011 Funny thing is, the D-D directions say to use RO water and not a calibration fluid. Mine too so was confused. This is my first Refractometer. Have you tried calling BRK or F&F? I tried BRK but I guess they were busy so I will again later. Link to comment Share on other sites More sharing options...
Ryan S December 30, 2011 Share December 30, 2011 Mine too so was confused. This is my first Refractometer. I tried BRK but I guess they were busy so I will again later. It looks like this: http://www.bulkreefsupply.com/store/aqua-craft-refractometer-calibration-fluid.html Link to comment Share on other sites More sharing options...
Origami December 30, 2011 Share December 30, 2011 Funny thing is, the D-D directions say to use RO water and not a calibration fluid. If it's a well designed and aligned scale, and it's temperature compensating, it'll probably be just fine and with minimal error. Certainly, distilled or RO/DI water should be more readily available than calibration fluid. The problem is that there are many calibration fluids out there and it's easy to misapply one. For example, using a 53 mS/cm fluid to calibrate a refractometer is bad practice; likewise using a 1.0264 sg fluid to calibrate the same. It's best to calibrate a particular instrument using a reference that was designed for it. Over the long haul, even with the D-D refractometer, it would probably be a good idea to verify it from time to time against a known standard, just to confirm that it hasn't fallen into misalignment. Link to comment Share on other sites More sharing options...
hypertech December 30, 2011 Share December 30, 2011 I disagree. Its best to calibrate these things with a solution that is near the point of interest. I could care less if its accurate at 1.010. I want to know if 1.026 reads correctly. If I calibrate at 1.026, then I know that point is correct and when it reads 1.026, that's what I have - not 1.022 or 1.030 from some scale error even though its accurate at zero. I want to know 1.026 is right when it says that. Link to comment Share on other sites More sharing options...
Origami December 30, 2011 Share December 30, 2011 I disagree. Its best to calibrate these things with a solution that is near the point of interest. I could care less if its accurate at 1.010. I want to know if 1.026 reads correctly. If I calibrate at 1.026, then I know that point is correct and when it reads 1.026, that's what I have - not 1.022 or 1.030 from some scale error even though its accurate at zero. I want to know 1.026 is right when it says that. Disagree with who or what? My recommendation is to calibrate around the point of interest. My other comment was regarding D-D's (the manufacturer) instruction, which is to use RO water. With a well aligned, designed, and compensated scale, calibrating with RO water will be fine, though perhaps not as accurate. Link to comment Share on other sites More sharing options...
hypertech December 30, 2011 Share December 30, 2011 Maybe I misunderstood your post. I thought you were saying calibrating with 1.026 was bad practice. Mea culpa. Link to comment Share on other sites More sharing options...
Coral Hind December 30, 2011 Share December 30, 2011 According Randy Holmes-Farley, using 53 mS/cm fluid to calibrate a refractometer is fine but you need to make sure it is made to 35ppt seawater. I use the American Marine / Pinpoint brand. His article: http://reefkeeping.com/issues/2006-12/rhf/index.php Link to comment Share on other sites More sharing options...
Origami December 30, 2011 Share December 30, 2011 True. But be sure that it's seawater reference. If it's saline, you need to match it to its intended equipment. (Sent from my phone.) Link to comment Share on other sites More sharing options...
hbh December 31, 2011 Share December 31, 2011 Ok. Since we are discussing this, could we possibly bring our refractometers to the next club meeting, Tom, & have a mini seminar of correct calibration? Please? Somewhat off topic, sort of sorry, but I get so lost on this topic! Link to comment Share on other sites More sharing options...
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