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Old 07-20-2010, 04:10 PM   #1
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Default ATC Refractometer - has anyone checked?

I am using an ATC Refractometer that I got off ebay for about $30 last winter. When I got it, I calibrated it (with my tap water) and things seemed to be working fine. I know you are "supposed" to calibrate with RO water, but I figure that since I brew with my tap water, then I should calibrate with my tap water since my tap water is what I want to consider "0".

Anyway.... My last few batches have been coming up short on OG and I had been chalking it up to me still being on the learning curve with my new system.

However, when cleaning up after a brew session Sunday night I happened to look through the refractometer with just tap water on it and found that it was reading BELOW 0 Brix. There's no scale below zero, but I estimate that it was at about -1.3 Brix.

Thinking that my calibration was simply off, I took the thing into the house with me and started typing an email to a friend who had also used it that night to let him know that the thing was reading badly.

I looked through it again to make sure it was really off by -1.3 so I could give him a better idea about how badly it was off , but the thing was reading apprixiately -0.2... same water that I had just saw reading -1.3... All I did was carry it into the house from the garage. WTF?

So, I took it back out to the garage and sat it on the workbench for about 10 minutes and looked through it again. Back at -1.3.

Thinking back when I got it, it was winter and the house would have been at about 68*F. That was the temp it was at when I calibrated, but it looks like my "ATC" doesn't work for sh!t.

0.0 @ 68*F (ambient temp when calibrated in winter)
-0.2 @ 78*F (ambient temp of house now in summer)
-1.3 @ 92*F (ambient temp of garage when I brewed)

Has anyone else actually checked to see if their ATC refractometer is really correcting the temp properly? An error of 1.3 Brix is pretty significant, IMO.

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Old 07-20-2010, 04:15 PM   #2
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Originally Posted by Walker View Post
I am using an ATC Refractometer that I got off ebay for about $30 last winter. When I got it, I calibrated it (with my tap water) and things seemed to be working fine. I know you are "supposed" to calibrate with RO water, but I figure that since I brew with my tap water, then I should calibrate with my tap water since my tap water is what I want to consider "0".

Anyway.... My last few batches have been coming up short on OG and I had been chalking it up to me still being on the learning curve with my new system.

However, when cleaning up after a brew session Sunday night I happened to look through the refractometer with just tap water on it and found that it was reading BELOW 0 Brix. There's no scale below zero, but I estimate that it was at about -1.3 Brix.

Thinking that my calibration was simply off, I took the thing into the house with me and started typing an email to a friend who had also used it that night to let him know that the thing was reading badly.

I looked through it again to make sure it was really off by -1.3 so I could give him a better idea about how badly it was off , but the thing was reading apprixiately -0.2... same water that I had just saw reading -1.3... All I did was carry it into the house from the garage. WTF?

So, I took it back out to the garage and sat it on the workbench for about 10 minutes and looked through it again. Back at -1.3.

Thinking back when I got it, it was winter and the house would have been at about 68*F. That was the temp it was at when I calibrated, but it looks like my "ATC" doesn't work for sh!t.

0.0 @ 68*F (ambient temp when calibrated in winter)
-0.2 @ 78*F (ambient temp of house now in summer)
-1.3 @ 92*F (ambient temp of garage when I brewed)

Has anyone else actually checked to see if their ATC refractometer is really correcting the temp properly? An error of 1.3 Brix is pretty significant, IMO.
ATC has a calibration temp and a range. I think you should check the literature that came with your tool and make sure you are using it in the proper environment and correctly.

And not being snarky, you should read about what ATC really does. IIRC, Kaiser has a good wiki on ATC. Unfortunately, ATC is often misunderstood.

In short. Calibrate at a conditioned room temp. Cool sample to a conditioned room temp. Take your reading at a conditioned room temp.
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Old 07-20-2010, 04:17 PM   #3
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Hmmm...I guess I haven't checked. Now you are making me all worried!

We check the readings with a refractometer and a hydrometer, but it is always at cooled temperature, near 68F.

Hmmmm...

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Old 07-20-2010, 04:21 PM   #4
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ATC has a calibration temp and a range. I think you should check the literature that came with your tool and make sure you are using it in the proper environment and correctly.

And not being snarky, you should read about what ATC really does. IIRC, Kaiser has a good wiki on ATC. Unfortunately, ATC is often misunderstood.

In short. Calibrate at a conditioned room temp. Cool sample to a conditioned room temp. Take your reading at a conditioned room temp.
I did read the little "manual" that came with the refractometer and it said to calibrate at 20*C, which is what I did (68*F).

However, that's all it says about temp being important for anything. The manual applies to several models (both ATC and non-ATC) and it says that if I do not have an ATC refractometer then I need to adjust the reading for the ambient temp, but if I have an ATC then I don't need to do anything.

Never says anything about needing to take the reading at a certain temp, or within a certain range.

I'll look up more info online and see what it says. The "manual" that came with my refractometer is pathetically short and is apparently lacking some relevant info.

Thanks!
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Old 07-20-2010, 04:29 PM   #5
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Some quick skimming on the web indicates that ATC works as long as you are within the range of about 68*F to about 85*F.

Which seems to make sense given what I was seeing.... pretty small error at 78*F vs 68*F, but large error when I got up into the 90's.

Problem solved. The good news is that this means that my efficiency did NOT drop when I started using the new system.

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Old 07-20-2010, 04:31 PM   #6
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Some quick skimming on the web indicates that ATC works as long as you are within the range of about 68*F to about 85*F.

Which seems to make sense given what I was seeing.... pretty small error at 78*F vs 68*F, but large error when I got up into the 90's.

Problem solved. The good news is that this means that my efficiency did NOT drop when I started using the new system.
Does that mean ambient AND liquid temp, or just ambient?
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Old 07-20-2010, 04:32 PM   #7
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This is for grape/wine folks, but reads OK: http://cefresno.ucdavis.edu/files/43066.pdf

The >90 degree temps we've been having are probably outside the compensation range. Your house is probably nicely air conditioned.

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Old 07-20-2010, 04:32 PM   #8
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I'll look up more info online and see what it says. The "manual" that came with my refractometer is pathetically short and is apparently lacking some relevant info.

Thanks!
I completely understand.

A proper spec should read like;

SPECIFICATIONS FOR HI 96811
Range
0 to 50% Brix / 0 to 80°C (32 to 176°F)

Resolution
± 0.1% Brix / ±0.1°C (±0.1°F)

Accuracy
± 0.2 % Brix / ± 0.3°C (±0.5°F)

Automatic Temperature Compensation
between 10 and 40°C (50 - 104°C)

Measurement Time
Approximately 1.5 seconds

Minimum Sample Volume
2 metric drops

Light Source
Yellow LED

Sample Cell
Stainless steel ring and flint glass prism

Case Material
ABS

Enclosure Rating
IP65

Battery Type / Life
(1) 9V / 5000 readings

Auto-Off
After 3 minutes of non-use

Dimensions
19.2(W) x 10.2(D) x 6.7 (H)cm

Weight
420g

Of course, the spec referenced is for a digital desktop refractometer cause, that is the first google link, but any proper spec should be as detailed.

Lack of info is the price we pay for cheap asian made Ebay knockoffs. But hey, at the manual was printed in broken engrish right?

Anyway, that temp spec is pretty typical. On another note, for wide swings within spec ranges you really shoulc let the optics acclimate to the chage in temp before taking your readings.

we all tend to rush things amidst the fast pace of brewing.

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Old 07-20-2010, 04:34 PM   #9
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Does that mean ambient AND liquid temp, or just ambient?
Ambient, mainly the temp of the refractometer itself. When you put a drop of liquid on it, it will very quickly equilibrate to the temp of the instrument.
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Old 07-20-2010, 04:35 PM   #10
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Ambient, mainly the temp of the refractometer itself. When you put a drop of liquid on it, it will very quickly equilibrate to the temp of the instrument.
OK, sounds good. And Phew! I was just about to go recheck all my beers.
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