refractometer help!

[claphamsa]

Ok, this weekend I used it for the first. time.... well first time i wasn't just messing around... preboil, it said we were about .013 high, and the volume looked about a gallon low, so i sparged another gallon. it was the only .003 high, so i went on to the boil. post boil, we were very close on volume, but it was .012 LOW on gravity! I checked it with clean water, as well as star san, and it was reading correctly then..... what did I do wrong? any help is appreciated!

 

[BargainFittings]

Did you account for thermal expansion on your volumes? Wort/water expands as you heat it.

 

[claphamsa]

Did you account for thermal expansion on your volumes? Wort/water expands as you heat it.

isnt the whole point of using a refractometer over a hydrometer that you can use it at any temp?

 

[Walker]

I think he meant when deciding on whether to add water or not and when you checked volumes.

 

[claphamsa]

I think he meant when deciding on whether to add water or not and when you checked volumes.

ah, i dont think the difference is THAT big is it?

 

[The Pol]

isnt the whole point of using a refractometer over a hydrometer that you can use it at any temp?

He means, what was the temp. when you checked the volume? Your volume will be greater if the wort is hot than it will be when it is cold.

Well, this is perplexing to a degree. What is your Brix correction factor?

If your refractometer is zeroed out, you are using the brix correction factor, and your volumes are ACCURATE, then there wil be no discrepancy.

 

[claphamsa]

well it zeroed with tap water and I goggled brixx readings...ugh.

 

[The Pol]

Ok, this weekend I used it for the first. time.... well first time i wasn't just messing around... preboil, it said we were about .013 high, and the volume looked about a gallon low, so i sparged another gallon. it was the only .003 high, so i went on to the boil. post boil, we were very close on volume, but it was .012 LOW on gravity! I checked it with clean water, as well as star san, and it was reading correctly then..... what did I do wrong? any help is appreciated!

This stuff all needs to be quite accurate. What was your exact pre-boil volume? What was your exact post boil volume? What was the gain bill? What was the pre-boil SG and post boil SG?

 

[The Pol]

well it zeroed with tap water and I goggled brixx readings...ugh.

Tap water cannot zero a refractometer accurately.

There will be a Brix correction factor that needs to be applied since wort has more in it than just water and sugar.

What was the ambient temp. when you "zeroed" the refractometer as opposed to the ambient when you tested the wort?

 

[claphamsa]

Tap water cannot zero a refractometer accurately.

There will be a Brix correction factor that needs to be applied since wort has more in it than just water and sugar.

What was the ambient temp. when you "zeroed" the refractometer as opposed to the ambient when you tested the wort?

oo, where do I find the correction? as for ambient temp, it was about 50 degrees outside... and I used tapwater (hose actually)

 

[Telix]

oo, where do I find the correction? as for ambient temp, it was about 50 degrees outside... and I used tapwater (hose actually)

If your refractometer came with instructions, which it should have, it almost certainly says calibrate with distilled water in a 68 degree ambient temp. If the temperature changes more than 5 degrees from that in your working environment you should recalibrate.

 

[The Pol]

oo, where do I find the correction? as for ambient temp, it was about 50 degrees outside... and I used tapwater (hose actually)

Yeah, the ambient temp will matter. The refract is probably ATC, but that means it cools the wort to ITS temp. If you calibrate it at 50F, then you have to use it at 50F.

You need to calibrate with distilled water.

Most people use a generic correction factor of 1.04, this varies slightly with each brewing system though. Mine is 1.054

EDIT: ATC only means there is no concern for the temp. of the sample, as it will assimilate to the temp of the instrument rather quickly. ATC function is only accurate in a certain range though, so calibrating at 50F will probably not suffice. The range is typically 68-86F. ATC will still require that you note the ambient temp. during calibration and while taking samples.

 

[springer]

Yeah, the ambient temp will matter. The refract is probably ATC, but that means it cools the wort to ITS temp. If you calibrate it at 50F, then you have to use it at 50F.

You need to calibrate with distilled water.

Most people use a generic correction factor of 1.04, this varies slightly with each brewing system though. Mine is 1.054

Pol thats not what an ATC refractometer does , an ATC refractometer needs no correction to be made for ambient temps. A non ATC would as it was calibrated at a set temp.

"Auto Temp. Compensation

Automatic-temperature-compensation eliminates the need for measuring temperatures and applying a correction factor when taking refractometer readings."

You will find this verbiage on every site that sells or makes ATC refractometers . Thats what ATC is for it doesn't correct for the temp of the sample to the unit. You need to let the sample sit a few seconds on the site glass so both are the same temp.

The unit should be calibrated with distilled water but if you are using tap water then it might be a good idea to use it to calibrate. Theory is the minerals in your tap water will also be in your wort . And what we are trying to find is how much sugar has been added to the water to make the wort.

 

[The Pol]

Pol thats not what an ATC refractometer does , an ATC refractometer needs no correction to be made for ambient temps. A non ATC would as it was calibrated at a set temp.

"Auto Temp. Compensation

Automatic-temperature-compensation eliminates the need for measuring temperatures and applying a correction factor when taking refractometer readings."

You will find this verbiage on every site that sells or makes ATC refractometers . Thats what ATC is for it doesn't correct for the temp of the sample to the unit. You need to let the sample sit a few seconds on the site glass so both are the same temp.

The unit should be calibrated with distilled water but if you are using tap water then it might be a good idea to use it to calibrate. Theory is the minerals in your tap water will also be in your wort . And what we are trying to find is how much sugar has been added to the water to make the wort.

I do know what ATC means. And you cannot calibrate an ATC refract at 50F and then check it at 80F and get the same reading. Try it. What is in bold above is correct, but you have to understand the instrument to know what they are saying. They are referring to the temp. of the sample, not the refractometer.

The calibration temperature of the refractometer. The most common calibration temp is 20° C or 68° F. If your sample is not exactly 68° F, you will need to make mathematical corrections to compensate for the temperature difference. Luckily, many modern models of refractometers (like the ones stocked by grapestompers) are sold with ATC (automatic temperature compensation), so you never have to worry about the temperature of your sample.

With ATC you do NOT have to worry about the temp. of the fluid you are measuring, but you do have to worry about the temp. of the instrument. The instrument doesnt know what temp. it is, so therefore it cannot make any "adjustment". It measures accurately at the temp. that the tool was calibrated. (so there is no flaming, there is a range yes... )

Everything I have read from ATC manufacturers states that you DO need to take note of the temp. of the instrument during calibration, as this will matter. ATC refracts are only ATC within a certain temp. range, and this is typically NOT below 68F.

From: http://cefresno.ucdavis.edu/files/43066.pdf

6. Check to make sure that an
ATC refractometer was used
within its range of 68-86ºF.

ATC only applies to sample temp. not instrument temp.

Then again, I dont know what ATC is.

 

[claphamsa]

wow, i didnt think i could get more confused than I was before...

 

[The Pol]

wow, i didnt think i could get more confused than I was before...

They are really simple to use. Like any tool, you have to know how to use them, and thier limits.

Calibrate at a reasonable temp. as stated in the link above from UC Davis.

Use the generic 1.040 Brix correction factor

Calibrate with distilled

Use the tool at the recommended temp. as stated in the link from UC Davis.

 

[springer]

I have to disagree with you POL


From the link you provided
see page three #2 on Calibrations.

"2. Note the temperature at the time
of readings. Most ATC refractometers
operate properly in the 68-86ºF
range. A laboratory or office at room
temperature should be used if outside
temperatures exceed the manufacturer's
recommended temperature
range."

If you place a drop on the prism and let it sit the temp of the sample will be the same temp of the unit even if it was 212°. That tiny sample in no way heats up the refractometer. So if you using the unit at room temps no correction is used as the sample and refractometer will settle at room temps.

While if you take the reading as soon as you place the sample on it it will be off but within a minute or two they will accurate

I agree if the initial calibration or the temps are out of the units range at the time of use then you need to correct.

"The calibration temperature of the refractometer. The most common calibration temp is 20° C or 68° F. If your sample is not exactly 68° F, you will need to make mathematical corrections to compensate for the temperature difference. Luckily, many modern models of refractometers (like the ones stocked by grapestompers) are sold with ATC (automatic temperature compensation), so you never have to worry about the temperature of your sample."

This even validates what I said

 

[The Pol]

I have to disagree with you POL


see page three #2 on Calibrations.

"2. Note the temperature at the time
of readings. Most ATC refractometers
operate properly in the 68-86ºF
range. A laboratory or office at room
temperature should be used if outside
temperatures exceed the manufacturer's
recommended temperature
range."

If you place a drop on the prism and let it sit the temp of the sample will be the same temp of the unit even if it was 212°. That tiny sample in now way heats up the refractometer. So if you using the unit at room temps no correction is used as the sample and refractometer will settle at room temps.
While if you take the reading as soon as you place the sample on it it will be off but within a minute or two they will accurate

I agree if the initial calibration or the temps are out of the units range at the time of use it then you need to correct.

"The calibration temperature of the refractometer. The most common calibration temp is 20° C or 68° F. If your sample is not exactly 68° F, you will need to make mathematical corrections to compensate for the temperature difference. Luckily, many modern models of refractometers (like the ones stocked by grapestompers) are sold with ATC (automatic temperature compensation), so you never have to worry about the temperature of your sample."

This even validates what I said

Ha ha... I love this.

Where did I say that the sample heats the refract? Never did. No argument there. The refract actually cools the sample within a miute or so. BUT this temp. needs to be within the ATC range, and the OP is way outside of that, which is where my posts are directed.

The OP calibrated well outside the ATC range, so therefore his calibration will be off. If ATC doesnt work outside that range, how can one calibrate outside that range?

You are saying the exact same thing that I am... but you are disagreeing?

Love it

 

[springer]

oo, where do I find the correction? as for ambient temp, it was about 50 degrees outside... and I used tapwater (hose actually)

Ok This is what I was missing I stand corrected the unit was out of its temp range when it was calibrated


Well PoL looks like were are on the same page my bad

 

[claphamsa]

thanks guys this is very helpful

 

[claphamsa]

so I need to use it only between 68- and 86

 

[claphamsa]

also, calibrate it at that temp, with distilled water.

 

[The Pol]

Ok This is what I was missing I stand corrected the unit was out of its temp range when it was calibrated


Well PoL looks like were are on the same page my bad

Good good... I was like WTF? This guy knows his s#it... why is he disagreeing?

Yes, he calibrated at 50F, so that should probably be done at a more reasonable temp. On my last brew session I took my ATC that was calibrated at 70F and happened to be using it in my garage at about 50F and it was off when checking with distilled.

ATC is awesome, but the temp. limits of the tool need to be respected for it to be accurate.

 

[The Pol]

also, calibrate it at that temp, with distilled water.

Yes, calibrate between 68-86F

Use distilled, or not, as Springer said

Yes take measurements in the ATC range, 68-86F

Great tools, once caibrated they are sweet, and much better than hydros.

 

[weirdboy]

It takes about 30 seconds to just calibrate your refractometer for current conditions at the start of your brew day. I keep around a bottle of distilled water and an eyedropper, put a couple of drops on there and adjust, and then I don't have to worry about it.

 

[claphamsa]

Good good... I was like WTF? This guy knows his s#it... why is he disagreeing?

Yes, he calibrated at 50F, so that should probably be done at a more reasonable temp. On my last brew session I took my ATC that was calibrated at 70F and happened to be using it in my garage at about 50F and it was off when checking with distilled.

ATC is awesome, but the temp. limits of the tool need to be respected for it to be accurate.

so what did you do in your case? to heat it up i mean?

 

[The Pol]

so what did you do in your case? to heat it up i mean?

Put it indoors so that the tool would be at the proper temp.

 

[Sockmonkey]

I bought a refractometer ($30 eBay model) a few years ago and never really bothered to understand how to use it. I thought it was plug-and-play like a hydrometer, and after some very confusing OG & FG readings on a few batches I assumed it was cheap junk and went back to the tried and true hydrometer.

Now that I've read this and several other refractometer threads, I think I understand how to use (and calibrate) it properly and see the benefits, particularly during the brewday. I still have one unclear point, however. Based on the BeerSmith refractometer tool, it seems that the refractometer can't be used for a FG reading? I need both a refractometer and hydrometer reading to caluclate the FG... which is silly to me (I'll just use the hydro reading).

Am I misunderstanding this?