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Refractometer calibration

sgarron

sgarron

NJRC Member
Is it best to calibrate with distilled water as the instructions state or to use something like pinpoint calibration fluid? With the distilled water you are calibrating at 0ppt. With the pinpoint solution you are calibrating at 35ppt, wich is the same number I want in my tank. I was just curious because I thought my salinity was right on target, I calibrated with the pinpoint and I am actually a little low, about 1.023 instead of 1.026.
 
C

chaoscat

I calibrate mine with the RO water from my filter. I also make sure the calibrating fluid is within a degree or 2 of my tank water. Does your refractometer automatically compensate for temperature differences? If not, do you equalize temps?

I was using the cheap floating beam hydrometer before and was appalled to find out my tank salinity was actually 1.028.
 
sgarron

sgarron

NJRC Member
My refractometer has ATC. I was just advised on reefcentral's chemistry forum that calibrating with the pinpoint solution is the best way to go. Because you are calibrating at the same point you want your water at. Makes sense to me.
 
malulu

malulu

NJRC Member
so, if you just calibrate it with RO water, was it at ZERO?

if it is also off, you then know for sure the Refractometer was off, and need adjustment.

if is is right on, then you will need to do more test & research - to know which one should you trust:
- the RO ???
- the pinpoint solution ::)
- just your factory defaulted setting... ;D
 
sgarron

sgarron

NJRC Member
I have calibrated it a few times over the last year with rodi or distilled water to zero. My water tested at 1.026. When I checked the pinpoint solution it read almost 40ppt. I calibrated with the pp to 35 and my wter tested low 1.023

I don't know??????? ???
 
malulu

malulu

NJRC Member
well, you have last for this wrong, it probably won't hurt to wait couple more weeks...
you can bring your Refractometer to the up coming meeting, i am sure we can help to figure out how to set it right.
;)
 
C

Carlo

It's pretty simple to me. ALWAYS use a calibration solution that is as close to the outcome as possible. In this case the Pinpoint 53ms. It really doesn't get much better then this.

Ideally, if you want to run your tank at 35% salinity or within a percent either way of it you can't get any better then calibrating the instrument with a 35% salinity solution (what the 53ms solution is).

Carlo

PS I really dislike the instructions that come with some meters that tell you to calibrate using RO water. It's at the wrong end of the scale and unless it LAB GRADE water may contain some salts that throw off the results.
 
J

JasonR

Maybe everyone should bring there refractometer to the meeting so we could compare everyone readings

Jason
 
Phyl

Phyl

Officer Emeritus
Officer Emeritus
RO is not perfectly accurate. It does get you close and you will be able to maintain a consistant salinity with it. A point up or down, but I don't think the exact position on the meter is as important as relative consistancy. We bought the calibration fluid and calibrated ours. It may have moved a point as a result, but overall I do believe close is good enough.
 
sgarron

sgarron

NJRC Member
I would probably take Randy's word over Pinoints myself. I was just showing what pinpoint showed as the value. At 5 one thousandths of a point difference, I don't think it really matters that much.
 
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