05XRunner Posted February 23, 2009 Author Share Posted February 23, 2009 her eis the one I got..man marineDepot is expensive http://www.marinedepot.com/ps_ViewItem~act...es~vendor~.html Link to comment
thetaylors Posted February 23, 2009 Share Posted February 23, 2009 yes it pays to shop around.. They are ok for somethings great for others and bad for a couple. Link to comment
coralcor Posted February 23, 2009 Share Posted February 23, 2009 we got a refract fight going on Link to comment
thetaylors Posted February 23, 2009 Share Posted February 23, 2009 rather be hit with a hydrometer than a refractometer.. Link to comment
Scott Riemer Posted February 23, 2009 Share Posted February 23, 2009 It's $4-5, I don't see the problem, people will pay that for a cup of coffee but we'll tell them it's unnecessary to double check their refractometer which could cause problems in their thousand dollar tanks. Guess that solid logic is lost on me. Link to comment
Pcyc Posted February 23, 2009 Share Posted February 23, 2009 just bought the ebay one we will see the results haha Link to comment
Scott Riemer Posted February 23, 2009 Share Posted February 23, 2009 sometimes good enough is good enough And what's "good enough" for you doesn't have to be "good enough" for me or anybody else. People can read and determine for themselves so why limit the options over a few dollars? Link to comment
jamesnmandy Posted February 23, 2009 Share Posted February 23, 2009 It's $4-5, I don't see the problem, people will pay that for a cup of coffee but we'll tell them it's unnecessary to double check their refractometer which could cause problems in their thousand dollar tanks. Guess that solid logic is lost on me. my logic is that if a $5 bottle of fluid is not available, then it's probably not worth it, because you will pay half the cost of a new refractometer for a bottle of fluid shipped to your door, only to find out more than likely that you refractometer is just fine, or maybe off by a single thousandth....which means nothing if i had a LFS that carried it and would sell it for $5 i would have grabbed it, but they would likely sell it for $10 or more since they sell $80 refractometers for $80, Koralia 4's for $60.....and maxi flow mods for $30....i consider $3 a few dollars, not $12-15 dollars, because another $10-12 dollars would buy me another new refractometer... also i explained my logic, my refracto was checked against several other devices, by the time you have a cross-sample that large, and knowing what we already know about how much the fluid would change things....i see no point in spending anymore time obsessing over it thats my logic, what i have is accurate at least to one thousandth, so i am not spending anymore time thinking or doing anything about it the results i get are just another testament of how perfectly fine it is And what's "good enough" for you doesn't have to be "good enough" for me or anybody else. People can read and determine for themselves so why limit the options over a few dollars? you're right, thats why i said i gave what info i had based on my results and my personal experience scott....like i said, you can continue to try to convince people they should buy fluid, and they can decide if they think its worth it or not....all we can do is give our opinions and experiences i havent seen you post that you bought fluid and found your refracto was way off compared to distilled method results...actually i havent seen anyone post that (other than the occasional defective unit), in which case a distilled-to-zero method would yield similarly incorrect results, if the unit is defective its defective, not only defective is calibrated using distilled.... we got a refract fight going on not at all, we are merely discussing our opinions on the subject and discussing our methods and results....this is good for those who are just learning about refracto's and calibration Link to comment
StevieT Posted February 23, 2009 Share Posted February 23, 2009 When you calibrate a scale, you use a known weight and start from there. You don't calibrate it from zero and expect it to weigh a 150 lbs package correctly. Same with a refractometer. You calibrate it at a known salt level since that is what you are testing for, not zero ie fresh water. For $5 and a lifetime supply, I choose accuracy againt a $3000+ tank. I calibrated my refractor with RO water, then with solution, solution won. Link to comment
05XRunner Posted February 23, 2009 Author Share Posted February 23, 2009 and where do you get this solution Link to comment
StevieT Posted February 23, 2009 Share Posted February 23, 2009 I shop online for almost everything. premiumaquatics sells it so does the good doctors. Save on shipping by purchasing other dry goods that you need anyway http://www.premiumaquatics.com/Merchant2/m...Code=Hydrometer Link to comment
NanoReefNovice Posted February 23, 2009 Share Posted February 23, 2009 lets just say it like this....my refracto has been checked against my hydro, my brother in laws hydro, and the LFS refractometer also.....taking all things into consideration, and cross-referencing between them taking into account the known variables.....no, it's really not worth $5 for me, but that's me for someone ordering one if they are able to get a cheap bottle of solution tossed in, sure, but i cant get a bottle of solution shipped to me for $5, more like $10 after shipping (none available locally) seriously guys, while i agree with being accurate, sometimes people take things to another unnecessary level Lets just say it like this... I have had the opposite experience with refrac accuracy. I have tested it against numerous professional refracs and hydros, they don't match up. There are too many varible to say your experience will be the same i.e. diffrents salts? Please read some litature on refracs b/4 you blindly trust it. ok scott, you win, im not spending anymore time trying to convince myself what i know to be true already Dude it that necessary, what about an intelligent discussion? Link to comment
coralcor Posted February 23, 2009 Share Posted February 23, 2009 sometimes good enough is good enough ok im gona have to agree with scott here because if you were going for good enough you coulda just kept the hydrometer but you got a refract to be accurate. but i also see where your coming from. money is tight. so 10-12$ use to be a few dollars now 2 is a few dollars. and if its not redily avalible. what did your LFS use to calibrate it? Link to comment
05XRunner Posted February 23, 2009 Author Share Posted February 23, 2009 ok im gona have to agree with scott here because if you were going for good enough you coulda just kept the hydrometer but you got a refract to be accurate. but i also see where your coming from. money is tight. so 10-12$ use to be a few dollars now 2 is a few dollars. and if its not redily avalible. what did your LFS use to calibrate it? 0 TDS RO water just like the directions say to use...and I checked it when I got home with my bottled DI water Link to comment
coralcor Posted February 23, 2009 Share Posted February 23, 2009 0 TDS RO water just like the directions say to use...and I checked it when I got home with my bottled DI water o well then wtf are you guys bickering about? Link to comment
Scott Riemer Posted February 23, 2009 Share Posted February 23, 2009 i havent seen you post that you bought fluid and found your refracto was way off compared to distilled method results...actually i havent seen anyone post that (other than the occasional defective unit), in which case a distilled-to-zero method would yield similarly incorrect results, if the unit is defective its defective, not only defective is calibrated using distilled.... Actually, to set the record straight, that is not true. I never had a problem with my refractometer. I started with a hydrometer that was off by .005. The reason I believe in calibrating with a "trusted" 35ppt solution is that I believe the potential exists to have a faulty and/or distorted prism. Hobbyists are looking for the best price and there's companies that may cut corners in quality to provide that lower price. That being the case, calibrating in the range of the fluid to be tested, in this case salt water, insures less of a chance for that *potential* distortion to skew the reading. Calibrating to 0 with distilled leaves a wider range for any error to compound. Link to comment
StevieT Posted February 23, 2009 Share Posted February 23, 2009 o well then wtf are you guys bickering about? Link to comment
coralcor Posted February 23, 2009 Share Posted February 23, 2009 stevie what i ment buy that is if the company you bought it from said use 0 tds water to calibrate... Link to comment
StevieT Posted February 23, 2009 Share Posted February 23, 2009 stevie what i ment buy that is if the company you bought it from said use 0 tds water to calibrate... ok, well I would expect that from a LFS knowing how some (or most) are but they should be using a calibration solution. Link to comment
coralcor Posted February 23, 2009 Share Posted February 23, 2009 ok, well I would expect that from a LFS knowing how some (or most) are but they should be using a calibration solution. yea......... idk this stuff is way over my head lmao Link to comment
05XRunner Posted February 23, 2009 Author Share Posted February 23, 2009 ok, well I would expect that from a LFS knowing how some (or most) are but they should be using a calibration solution. wasnt from the fish store..says right on the directions that came with it..use Distilled water to calibrate Link to comment
StevieT Posted February 23, 2009 Share Posted February 23, 2009 wasnt from the fish store..says right on the directions that came with it..use Distilled water to calibrate yeah, I have seen the directions, same thing came with mine and it doesn't make it the best way to calibrate a refractor. I was under the assumption that the LFS calibrated it for you, and with RO water. Either way, I think the information you need has been posted. I first calibrated mine with RO/DI, then after a month with solution, the RO/DI was off by enough to make me wonder. Link to comment
Scott Riemer Posted February 23, 2009 Share Posted February 23, 2009 Calibrating to 0 with distilled leaves a wider range for any error to compound. Link to comment
neanderthalman Posted February 23, 2009 Share Posted February 23, 2009 When you calibrate a scale, you use a known weight and start from there. You don't calibrate it from zero and expect it to weigh a 150 lbs package correctly. Same with a refractometer. You calibrate it at a known salt level since that is what you are testing for, not zero ie fresh water. For $5 and a lifetime supply, I choose accuracy againt a $3000+ tank. I calibrated my refractor with RO water, then with solution, solution won. Interestingly, whenever you use a good scale, it does get calibrated to zero before using it. OMFG! Yes, it's best to calibrate using a solution, just as it would be best to calibrate a scale against a mass identical to the package you are weighing. Calibrating with RO/DI works just as well almost every single time, so unless you've got it on-hand, just use RO/DI. Next time you order some stuff online, add a bottle of calibrating solution to your order. It's cheap, but don't bother with an order just for it. It's not "mission critical". The problem with the floating hydrometers is that the accuracy is really poor on anything bought for the purpose. Cheaply made, cheaply sold. For all arguing in this thread, here's a primer so you can actually communicate accuracy and precision properly regarding your instruments. You're driving me nuts. Other items or terms of note. Precision: Repeatability of measurements - property inherent to a device. Not subject to calibration Accuracy: A measure of "closeness" to the expected or true value. Can be corrected via calibration. Drift: The rate at which the accuracy of a device declines after calibration. Linearity: How well a calibration at one measurement provides accuracy at another measurement. Does not change significantly over time. Error: Difference between measurement and known standard. Used only when calibrating. Ok, let's clear this up. Swing-arm hydrometers are lowest in both accuracy and precision. There are a lot of factors, like bubbles, crud, level surface, conditioning (initial soak), that all work against both accuracy and precision. The fat needle does not help either. Drift can be quite high, for example, if left dry for a long time. Glass hydrometers are better for precision, but not much more accurate, and could even be less accurate than a swing arm. The paper slip inside could be sitting literally anywhere. However, the advantage here is that it's a sealed unit with a constant density. So long as you keep the surface clean, and the paper inside is firmly fastened, then there will be nearly zero drift. That means that you can calibrate it once, and never have to calibrate it again. They are difficult to use, and difficult to read, as you either have to fill a tall vessel, or turn off all your pumps, and then try to read through the meniscus (curved water at glass-water interface). Calibration of a glass hydrometer would require a calibrated refractometer to measure the water, then measure the same water with the hydrometer. Accuracy of one order of magnitude is lost when you do this, so you'd better hope that the solution is accurate to at least 35.0 PPT. Put simply, refractometers are superior for both accuracy and precision. The gradations are quite fine in a good refractometer, and repeatability is excellent, so you're looking at a precision of about 0.5 PPT or .0005 SG, depending on the scale you use. Accuracy out of the box can be pretty bad, but the calibration is quite simple, so this is not an issue. However, there is a lot of misinformation regarding how you have to calibrate your refractometer. Someone made laughing reference to calibrating a speedometer against 0. Nothing wrong with that. In fact, in most cars it's better than calibrating against the top end of the scale. Think about it. In refractometer terms - that's equivalent to saying that calibrating at 0 is no better than calibrating at 75 PPT. Neither situation is as good as calibrating at 35PPT or 60MPH, of course, but it's not without value. This is where linearity comes into play. Linearity on most refractometers is quite good. Mine personally is less than 1%. What does this mean? Here's how you can determine, roughly, the linearity of your refractometer. You should get a pack of 35PPT (53mS) solution with your refractometer. Calibrate it to 35PPT, then measure RO/DI. If you read zero, then your linearity is spot on like mine. (1% means an error of about 0.35 over this span). It will never change. At this point, you know that if you calibrate to RO/DI, then your measurement of 35PPT will be within about 0.35PPT. That's plenty accurate. Save your money, even if it is only a couple bucks. Link to comment
Scott Riemer Posted February 23, 2009 Share Posted February 23, 2009 Crap! N-Man found us. Link to comment
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