Refractometer..Is this a good purchase?

[NadoHawk]

http://www.homebrewfinds.com/2014/04/dual-scale-refractometer-wcorrected.html

I am looking to get one for both measuring alcohol content (yes...I'm willing to do the math for post fermentation calculations). I also want it for testing my all-grain brewing when I finally get my kit finished.

 

[gr8shandini]

It doesn't seem to be a bad deal. However, it appears to have a plastic body. For a couple of bucks more, you can find examples with an aluminum body. Your call if it's worth the extra cash or not.

And for what it's worth, I'd personally avoid a dual scale model. They're hard enough to read as is without cluttering up the reticule. And the math is really simple. If you're not a high gravity guy, Brix*4 gets you close enough. If you're routinely brewing over 1.060 you might want to actually do the conversion or keep a table handy. But that's just me.

 

[IvanTheTerribrew]

I'd agree don't skimp money on a refrac. And I'd advice against getting dual scale. Try to get one that is just brix. I have never heard of a dual scale that is actually accurate.

One thing too.. To calibrate it, I suggest using the same water you're going to brew with. Someone said that to me and it makes sense. If the difference between your liquor (brewing water) and distilled water is 0.2 brix... Then if you calibrate with distilled but then use the other, you're constantly off at least by that much.

But a refrac is a great investment for AG. It's nice to easily take final runnings gravity, preboil gravity, etc. Cheers


- ISM NRP

 

[WI_Wino]

For what's it worth I have a dual scale refractometer from amazon and the SG side was accurate right from the box. I measured against distilled water and a known wort SG (xx cups of DME in xx cups of water to get to 1.040, forget the exact measurements). Also measured against my hydrometer bought years ago and they both agree.

Here's the one I think I got: http://www.amazon.com/dp/B00AOCKWJI/?tag=skimlinks_replacement-20

 

[mdabbles]

Best use I have found is for measuring unfermented wort gravity. Have not yet trusted formulas for alcohol.

Sent from my C5155 using Home Brew mobile app

 

[skuhn2004]

I've found mine useful. I use the calculator in the link and it's very close to what my hydrometer is telling me. The nice thing is taking samples only uses a few drops instead of a few ounces required for a hydrometer reading. In the end you are still looking for the same gravity 3-4 days apart to know that fermentation is done.

Some don't, but I trust the refractometer when I get the same reading 3 days apart and my FG is within +/-


http://onebeer.net/refractometer.shtml

 

[leadgenm]

I bought my refractometer from National Microscope Exchange.
https://www.nationalmicroscope.com/refractometers.html

Product which you asked here is available on National Microscope Exchange store on discounted price.

 

[charliehorse]

When I kept saltwater fish, I used a refractometer, so when I started brewing, I bought a refractometer. It just made sense. As far as the dual scale goes, I don't mind it. Prior to brewing, I had no idea what a brix was but I knew exactly what specific gravity was, so I don't even bother looking at the brix scale. I use it to verify my target gravities and the software takes care of the ABV calculations for me (not that I care since most of the stuff I brew is in the 7.5-8% range).

 

[billl]

"For what's it worth I have a dual scale refractometer from amazon and the SG side was accurate right from the box. I measured against distilled water and a known wort SG (xx cups of DME in xx cups of water to get to 1.040, forget the exact measurements). Also measured against my hydrometer bought years ago and they both agree."

Sorry to tell you, but it probably wasn't/isn't accurate. The approximation 4X approximation they use to convert Brix to SG is pretty close to the 1.040 range, but it breaks down the higher you get. If you brew a big beer, or even are just checking the first runnings, you'll be short.

", I had no idea what a brix was but I knew exactly what specific gravity was, so I don't even bother looking at the brix scale. "

Then all of your measurements are likely slightly low. The conversion they use from brix to sg underestimates SG in the higher ranges. It's not a big deal 99% of the time, but it is something to be aware of.

 

[broadbill]

Sorry to tell you, but it probably wasn't/isn't accurate. The approximation 4X approximation they use to convert Brix to SG is pretty close to the 1.040 range, but it breaks down the higher you get. If you brew a big beer, or even are just checking the first runnings, you'll be short.

Can you elaborate on why you didn't think his approach would not have resulted in determining the refractometer was accurate or not? Also, he didn't say he used the 4x approximation here.

I thought using a calibration standard (the x amount of DME in water) after zeroing it to distilled water was a pretty solid way of determining accuracy. Its more than I typically do (just zero to distilled water). He could have used two calibration standards, but that is probably overkill.

 

[WI_Wino]

Can you elaborate on why you didn't think his approach would not have resulted in determining the refractometer was accurate or not? Also, he didn't say he used the 4x approximation here.

I thought using a calibration standard (the x amount of DME in water) after zeroing it to distilled water was a pretty solid way of determining accuracy. Its more than I typically do (just zero to distilled water). He could have used two calibration standards, but that is probably overkill.

There might be something to this. I did 15 gallons of carmenere/merlot (Chilean harvest) about month ago and my hydrometer and refractometer were not lining up. If I recall correctly, hydrometer was showing ~1.105 and the refractometer was showing ~1.090. I was in a rush so I went with the hydrometer (easy with wine as you don't have to cool anything). But I am also not sure if the grapes had released all of the sugar into the juice yet. So perhaps the refractometer was reading the juice properly and the hydrometer was taking into account the sugars still in the grapes?

For the beers I make, being accurate at 1.040 is good enough for now. I do need to figure out something for the wine before the fall. Might be as simple as just using the brix side and doing a quick conversion.

 

[MW66]

I bought this one and it was right on. I calibrated it first with distilled water as directed. Using this for OG is great, but I have not tried it for FG with the calculations. I like to take a taste sample anyways at the end before carbonation and dry hopping, so I'll probably continue to use my hydrometer for FG readings.

http://www.amazon.com/gp/product/B006GG0TDK/?tag=skimlinks_replacement-20

 

[billl]

"Can you elaborate on why you didn't think his approach would not have resulted in determining the refractometer was accurate or not? Also, he didn't say he used the 4x approximation here.

I thought using a calibration standard (the x amount of DME in water) after zeroing it to distilled water was a pretty solid way of determining accuracy. Its more than I typically do (just zero to distilled water). He could have used two calibration standards, but that is probably overkill."

Every refractometer I've ever seen uses the 4x adjustment. The actual version is non-linear.

Calibrating a refractometer at 2 points works just fine - for brix and plato. It's the conversion from those to SG that doesn't work.

SG = 1+ (plato / (258.6 – ( (plato/258.2) *227.1) ) )

When the gravity is low eg 10 plato or 1.040, the (plato/258.2*227.1)=8.8 so SG = 1 + plato/(258.2-8.8) = 1+plato /(249.4) = 1+.001*4.0096*Plato. Pretty darn close for 4x.

When gravity is higher eg 20 plato, you get SG = 1+plato/(258.2-17.6) = 1+plato/(240.6) = 1+.001*4.156 plato. The difference is much larger. 0.156*20 = 3.1, so the 4x estimate would be low by 3 points.

Again, not a huge deal most of the time. However, if you use the approximation to get the OG and then another approximation to get FG, and then another approximation to correct the FG reading for alcohol (that was already off a couple points from the first approximation) ...... suddenly you're significantly off.

 

[broadbill]

"Can you elaborate on why you didn't think his approach would not have resulted in determining the refractometer was accurate or not? Also, he didn't say he used the 4x approximation here.

I thought using a calibration standard (the x amount of DME in water) after zeroing it to distilled water was a pretty solid way of determining accuracy. Its more than I typically do (just zero to distilled water). He could have used two calibration standards, but that is probably overkill."

Every refractometer I've ever seen uses the 4x adjustment. The actual version is non-linear.

Calibrating a refractometer at 2 points works just fine - for brix and plato. It's the conversion from those to SG that doesn't work.

SG = 1+ (plato / (258.6 – ( (plato/258.2) *227.1) ) )

When the gravity is low eg 10 plato or 1.040, the (plato/258.2*227.1)=8.8 so SG = 1 + plato/(258.2-8.8) = 1+plato /(249.4) = 1+.001*4.0096*Plato. Pretty darn close for 4x.

When gravity is higher eg 20 plato, you get SG = 1+plato/(258.2-17.6) = 1+plato/(240.6) = 1+.001*4.156 plato. The difference is much larger. 0.156*20 = 3.1, so the 4x estimate would be low by 3 points.

Again, not a huge deal most of the time. However, if you use the approximation to get the OG and then another approximation to get FG, and then another approximation to correct the FG reading for alcohol (that was already off a couple points from the first approximation) ...... suddenly you're significantly off.

and again, he never said he was using the 4x approximation. He was describing his calibration process which has nothing to do with Brix to SG conversation.

Point taken about the conversation not being linear. There are conversation tables based on your equation, if people are that worried, they can just rely on that for conversation. That is what I do.

 

[billl]

"and again, he never said he was using the 4x approximation. He was describing his calibration process which has nothing to do with Brix to SG conversation."

And again, that is just how the "dual" guages are - at least all the ones I've seen. The SG scale is just printed that way.

And yes, the "calibratation" most certainly has something to do with the conversion. If you calibrate your standard dual scale refractometer with the SG side at 1.040, it will show 1.080 when the gravity is 1.083. For anyone just looking at the SG side, this will be a continual source of error in their measurements.

 

[mtnagel]

The problem is that the SG scale is wrong at higher brix/SG values so if he calibrated at 1.040, you wouldn't really be able to tell because the brix and SG aren't really off that far at that point.

My refractometer is below. It's easy to see it's off. Use this calculator and type in 30 brix. The resulting SG is 1.1292, which isn't even on the SG scale.

I calibrated mine using sugar solutions of known brix values and my refractometer is accurate on the brix side, but not the SG side. I posted my method and results here. I only use the brix side now. Wish I would have just gotten a brix only one.

 

[broadbill]

"and again, he never said he was using the 4x approximation. He was describing his calibration process which has nothing to do with Brix to SG conversation."

And again, that is just how the "dual" guages are - at least all the ones I've seen. The SG scale is just printed that way.

And yes, the "calibratation" most certainly has something to do with the conversion. If you calibrate your standard dual scale refractometer with the SG side at 1.040, it will show 1.080 when the gravity is 1.083. For anyone just looking at the SG side, this will be a continual source of error in their measurements.

I don't know about the dual gauges as I don't have that version. I wouldn't think they would be inaccurate in the ranges printed on the reticule but I could be wrong. But if that is what you were referring to all along, it would have been helpful if you stated that you were referring to the dual gauge and not the calculation a brewer would do in their head, which is the typical use of the 4x rule (after all, if they had a dual guage they wouldn't be converting in the first place!).

As far as calibration goes it can just as easily be done all in brix.