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Author Topic: Refractometer?  (Read 4169 times)

Offline hankua

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Refractometer?
« on: February 24, 2015, 07:09:39 AM »
I managed to win a new Misco Palm Abbé PA202 on EBay for less than half the retail price. I think it's very similar to the VST meter, a PA203 with custom software and upgraded optics. The 202 has two scales, brix and refractive index.

Anything VST is pretty controversial on coffeegeek but interesting none the less. I found two formulas in one of the threads: TDS=545*nD-726 and in the next paragraph TDS=560*nD-746. The other formula is brix x .85, I think RI is the more accurate scale to use. And it's possible to use other scales, not sure if there relevant; specific gravity?

Question is, has anyone used a digital refractometer with both brix and RI scales?
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Offline John F

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Re: Refractometer?
« Reply #1 on: February 24, 2015, 11:44:48 AM »
I have a refract I use for brewing beer to hit a specific gravity I'm after.

I've never thought about looking at coffee in it.
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Offline Joe

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Re: Refractometer?
« Reply #2 on: February 24, 2015, 12:03:34 PM »
you might be able to check if proper water to coffee ratio was achieved?
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Offline John F

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Re: Refractometer?
« Reply #3 on: February 24, 2015, 12:06:54 PM »
My mouth does that.   ;)
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Offline peter

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Re: Refractometer?
« Reply #4 on: February 24, 2015, 01:50:38 PM »
Quote from: John F on February 24, 2015, 12:06:54 PM
My mouth does that.   ;)

Hahahaha!!!

But that's not geeky enough.  Forget what your palate tells you; you must use a gadget to determine if it's good or not.   ;D
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Offline Joe

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Re: Refractometer?
« Reply #5 on: February 24, 2015, 02:03:58 PM »
Ok but regardless I bought a cheap Amazon refractometer for like $15 way back when still works amazingly and I wouldn't spend a penny more for what it does. Back when I bought mine they were like $80+ for a domestic product.

Ummm...I might drag mine out to see what the numbers do
« Last Edit: February 24, 2015, 02:08:58 PM by Joe »
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Offline hankua

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Re: Refractometer?
« Reply #6 on: February 24, 2015, 02:40:43 PM »
Quote from: Joe on February 24, 2015, 02:03:58 PM
Ok but regardless I bought a cheap Amazon refractometer for like $15 way back when still works amazingly and I wouldn't spend a penny more for what it does. Back when I bought mine they were like $80+ for a domestic product.

Ummm...I might drag mine out to see what the numbers do


How did you use the results?
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Offline hankua

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Re: Refractometer?
« Reply #7 on: February 24, 2015, 02:46:58 PM »
Quote from: John F on February 24, 2015, 11:44:48 AM
I have a refract I use for brewing beer to hit a specific gravity I'm after.

I've never thought about looking at coffee in it.
We use densitometers and beer analyzers at work that read SG, ASBC Balling, and Plato balling. Beer results are always reported using the Plato scale.
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Offline Ascholten

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Re: Refractometer?
« Reply #8 on: February 24, 2015, 04:58:05 PM »
densiometer?  Is that to measure when someone on the board gives a really obtuse answer to something? :D

Aaron
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Offline hankua

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Re: Refractometer?
« Reply #9 on: February 24, 2015, 05:47:37 PM »
Well I took a stab at this and ran a sample from the office coffee pot. Got 1.3348 nD unfiltered and 1.3348 nD paper filtered (lab quality). I'm confused why there are two different formulas in the same coffeegeek post. If my math is correct it worked out to 1.466 and 1.488 tds.
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Offline John F

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Re: Refractometer?
« Reply #10 on: February 24, 2015, 06:12:18 PM »
I also have tds meters...you just stick it in the fluid and it gives you a digital tds reading.

Are they giving you some sort of equation/formula to use a refractometer to calculate tds?

« Last Edit: February 24, 2015, 06:18:11 PM by John F »
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Offline hankua

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Re: Refractometer?
« Reply #11 on: February 24, 2015, 08:39:08 PM »
Quote from: John F on February 24, 2015, 06:12:18 PM
I also have tds meters...you just stick it in the fluid and it gives you a digital tds reading.

Are they giving you some sort of equation/formula to use a refractometer to calculate tds?

Not really, I found a formula on coffeegeek. Refractive index is supposed to be the most accurate method other than drying out the coffee sample. Maybe I should try drying out a sample and compare it to the digital refractometer?
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Offline John F

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Re: Refractometer?
« Reply #12 on: February 25, 2015, 07:14:24 AM »
I've never heard of that before but it's interesting.

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Offline hankua

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Re: Refractometer?
« Reply #13 on: February 25, 2015, 09:39:58 AM »
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Offline John F

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Re: Refractometer?
« Reply #14 on: February 25, 2015, 10:00:23 AM »
If you do wind up testing digital TDC meter vs the refractometer equation vs drying out samples let us know what you find out.

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