Refractometer purchase

[Xolsiion]

I'm looking for suggestions for refractometers please.

Also - can someone explain what makes over a 100% price differential between the 40$ refractometer and the 90$ ones on marinedepot.com? I tried to put links but they didn't work for some reason - just search for 'refractometer' and they'll be the first ones to come up...

 

[shuguley]

I bought the $40 refractometer from marine depot, it works great and I'm very happy with it. I think some of the more expensive ones might have a light built in, whereas the cheaper ones you have to hold under a light. There might be some other un-needed features as well. If I had to do it again, I would still buy the $40 one.

edit: I just looked at the two you mentioned, looks like the only difference is, the expensive one has a thumb screw calibration dial, the cheaper one has a screwdriver calibration dial.... not worth the 100% price increase IMO.

 

[chris4869]

You need the calibration fluid to recalibrate it for salt water use. Don't trust the precalibration in the unit.

 

[abulgin]

After reading a bunch of reviews from others on RC, I bought mine on eBay for like $30 (with shipping) and it's great. Make sure you get one that can be calibrated and that has automatic temperature correction (ATC). IMO, there is no reason to spend even $40 when there are so many decent ones available via eBay for less.

Go to ebay and search item "230334015632". That's the same one I got. $23.99 plus $9.99 shipping.

As stated above, you should also get the Pinpoint calibration fluid, and JCAquatics sells some on eBay for $5, plus $5 shipping. See item "350128308166".

 

[drparker]

+1 on the $40 unit plus cal fluid. I got my from Drs Foster & Smith.

 

[PRDubois]

$40 refractometer from marine depot, it works great and I'm very happy with it

 

[kraze3]

I have the 40 dollar one from Drsfostersmith also. Deff get the calibration fluid.

 

[Xolsiion]

I was kind of curious if the thumb-screw calibration rather than the enclosed screwdriver was the only difference. Having a light makes sense too, but I agree - not worth that much more money.

Now the 40$ one mentions using some distilled water and calibrating to 0. What's the advantage of the calibration fluid vs distilled water? How often does everyone recalibrate/check their calibration for their refractometer?

 

[Kenmx10]

I got the $90.00 one. It works great. I paid $15.00 for it used.

 

[mg426]

It is more important to have the instrument read correctly than how much it costs. I would be getting some calibration fluid and verify that it is accurate. Calibration fluid will allow you to verify the accuracy at the point at which it will be used. 1.026. RO/DI water only verifys the zero point.

 

[drparker]

<a href=showthread.php?s=&postid=14748084#post14748084 target=_blank>Originally posted</a> by Xolsiion
I was kind of curious if the thumb-screw calibration rather than the enclosed screwdriver was the only difference. Having a light makes sense too, but I agree - not worth that much more money.

Now the 40$ one mentions using some distilled water and calibrating to 0. What's the advantage of the calibration fluid vs distilled water? How often does everyone recalibrate/check their calibration for their refractometer?

I check mine monthly. These instruments can have slope errors, meaning the farther away from the calibration point you get the bigger the error becomes. So when you calibrate to zero it's accurate at zero but might not be accurate at 1.0264 which is natural sea water. By using the calibration fluid your calibrating to 1.0264 so you knows that when it reads in that range it's dead on.

When I first got mine I used distilled and calibrated to zero and ran my tanks at 1.0264. Months later I read Randy's article on refractometers and ordered the solution. When calibrated to 1.0264 I found my previous readings were off and I was really running at 1.024 not the 1.0264 I had thought I was.

The solution runs 5 bucks and lasts forever. I can't imagine spending the money for a refractometer and not spending 5 bucks more to make sure it's accurate.

 

[Xolsiion]

What I was most concerned about was that the 40$ version wasn't any good, but that doesn't seem to be the case. Seems like you pay more for ease of use rather than effectiveness.

drparker - thanks for the info on the calibration fluid and slope error. That article is in reefkeeping magazine somewhere?

Anyone else care to offer how often they check or recalibrate?

thanks for all the responses

 

[mg426]

I calibrate/verify mine about UH, UM, whenever I think of it. It has always been spot on after calibration that is. I use the pinpoint calibration solution You can find it here www.premiumaquatics.com

 

[drparker]

Here's the article. http://reefkeeping.com/issues/2006-12/rhf/index.php

 

[BradMugs]

Interesting - went to EBay and the $30 including shipping one looks to me like the $90 marine depot one (with the finger adjustment).

 

[Xolsiion]

Thanks for the article drparker, that answered all my questions.

 

[THE ROOK]

I also bought the ebay unit. It's works great. No need to pay any more, IMO. As mentioned, calibration fluid is needed for any unit.

 

[usmcmp2006]

bulk reef supply has a good one and right now they are giving the calibration fluid for free with the purchase...