Refractometer: Calibration

[Unarce]

Just wondering how often reefers calibrate their refractometers. If you happen to have the American Marine Salinity Monitor, I'd also like to know how often you calibrate that one, too.

TIA

Karl

 

[Anonymous]

I calibrated mine once in five years. That was about 6 months ago, so I'll have to do it again in 2011.

Louey

 

[gregb1]

I thought this had to be done more often.

 

[GSchiemer]

Refractometers should be calibrated frequently, if not each time you use it. I typically use deionized water and calibrate it to "zero." Salifert sells a calibration solution (35 PPT), which, IME, works very well.

 

[Jimmy G]

I calibrated mine once in five years. That was about 6 months ago, so I'll have to do it again in 2011.

Louey

Hey Louey, do me a favor, check your salinity then clean and calibrate and test again. Let us know how close your readings are.

I haven't calibrated mine in 6 years :lol:

 

[GSchiemer]

What's the point of purchasing a precision instrument only to ignore the minor, but important, step of calibrating it? You may as well have stuck with that $5.00 plastic swing-arm hydrometer. It's simply foolish and reckless to imply that's it's okay to calibrate it every 5 or 6 years.

Salinity is a critical component in a reef aquarium and it's nothing to fool around with. The readings on refractometers do drift over time and the instrument should be calibrated regularly. They wouldn't build in this capability if it weren't necessary.

 

[Anonymous]

The instructions to my refractometer, a Sybon FG100sa, states "In the long run, however, the FG100sa may be recalibrated". Not exactly a strong endorsement for regular recalibrating.

The one time I did reclaibrate mine, I only had to turn the screw a very minor amount to dial it in to a sg of 1.00. I was very careful, as the instuctions indicated, to do the calibration at 20 degrees C.

I then rechecked the salinity of my saltwater and got the exact same reading.

I am sure Greg is right though. Better safe than sorry.

Louey

 

[GSchiemer]

A lot of the refractometers in the aquarium marketplace are cheap knock-offs made in China, so I wouldn't put much stock in the instructions.

I have a refractometer that was manufactured in Japan and purchased from a laboratory supply house over 10 years ago. It cost hundreds of dollars at the time (and still does). I actually inherited it from a reef buddy of mine that died many years ago. It's recommended to calibrate it before EVERY use. I don't go that far but I do check the calibration at least monthly. I've been surprised a few times by how far it's drifted.

Greg

 

[Anonymous]

It's interesting, Greg.

Mine cost something like $65. Maybe less.

Even though it's apparently a cheapy, it would stand to reason that it should be calibrated at least as freqeuntly as the more expensive ones, if not even more often.

I shall recalibrate mine before I do my 120G WC this weekend.

Louey

 

[Jimmy G]

I was exaggerating. I have atually calibrated mine about 4 or 5 times over the years. I think I will do it again. I remember the instructions saying to use distilled water. Would it make a difference if I used some RO/DI do you think?

 

[Anonymous]

I use(d) RO/DI water.

Louey

 

[GSchiemer]

I was exaggerating. I have atually calibrated mine about 4 or 5 times over the years. I think I will do it again. I remember the instructions saying to use distilled water. Would it make a difference if I used some RO/DI do you think?

RO/DI water is fine.

 

[Anonymous]

I checked my calibration today and it didn't need any adjustment. Of course the one time that I did recalibrate it over the last 6 years was only about 6 months ago. That time it did need adjustment.

Louey

 

[Unarce]

Thanks for all the replies!

I'm a little disappointed in the AM Salinity Monitor I have. I calibrated it as soon as I got it. Two months later, I ran a measurement and got 1.0236, than recalibrated it. The next measurement after recalibration was 1.0260.

It's off-putting to think it would drift this far after only two months. It would seem I need to calibrate this thing at least once a month to stay consistent :?

 

[Anonymous]

I have the AM salinity monitor and it lives in a box. Never could trust it. I am happy I didn't buy it.

I now check my refracto with DI every time I use it. If I don't check it, no matter how carefully I clean it off, the reading seems to be effected by residual salt on the lens.

 

[Anonymous]

I have the AM salinity monitor and it lives in a box. Never could trust it. I am happy I didn't buy it.

I now check my refracto with DI every time I use it. If I don't check it, no matter how carefully I clean it off, the reading seems to be effected by residual salt on the lens.

I used to keep a dedicated turkey baster for hosing off my refrac meter; I'd rinse it after every use and make sure the (lid? cap?) got rinsed as well.

 

[Anonymous]

>...Would it make a difference if I used some RO/DI do you think?

It does not matter if you use RO/DI or tap water to calibrate it. The amount of salt in tap water is so minute compare to seawater that refractometer does not see any different. But then, a few drops RO/DI is not that expensive, but it just a bit of paranoid when people *insists* to use RO/DI for calibration of refractometer.

GSchiemer is correct that you should calibrate it regularly. Some of these knockoff probably does not do much when it comes to ATC (auto temp. compensation). I don't bother to open one up to make sure the mechanism is there, but if just remember you get what you pay for, you won't be surprised.

As for the salt residue on the lense that affect the reading... I don't know Righty. If it does not dissolve, it is not going to affect much. See if you can use some vinegar to clean the optic, and make sure to clean it after each use.

 

[Anonymous]

We calibrate ours every use where I work, and I do the same at home.

 

[Anonymous]

Just like we calibrate our PH meters every use