new refractometer - measurements off

hoboscratch · Post by **hoboscratch** » Mon Feb 14, 2011 10:55 am

So I got a refractometer for xmas and just used it for the first time yesterday. I zeroed it using distilled water, like the instructions say. I took a sample of my preboil gravity and it was way lower than I would have expected. I took a hydrometer reading, which I've verified in the past is zeroed with distilled water at 60F. It was about 3-4 points higher, which was in line with what I was shooting for.

After the boil I took my OG reading and the refractometer read it as 1.043, my hydrometer measured it at 1.050 @ 70F. I also used the refractometer inside, since the instructions stated as such. Just in case I also re-zeroed my hydrometer using distilled water again. Its spot on.

Anyone have issues with a damaged refractometer? I imagine they're pretty sensitive but this was pretty lame.

DrPaulsen · Post by **DrPaulsen** » Mon Feb 14, 2011 11:09 am

The only issue I've ever had with my refractometer was temperature related. It has ATC, but that still only works over a limited temp range and will not work outside in the middle of January. Nowadays, I leave it in the house between readings on brew day. After I splash some wort across the lens, I take it back inside and let it settle for 5-10 minutes to make sure the ATC has had time to kick in. I have no idea how the ATC works, but I've noticed the reading will move over the course of a few minutes (they typically go up). It doesn't sound like that's your problem exactly, but maybe letting it settle for a few minutes would help?

Perhaps you could try working up some calibration solutions (1.020, 1.040, 1.60, etc.) and compare your refractometer and hydrometer. Another option would be to bring a calibration solution to a club meeting and compare it with someone else's refractometer.

Matt F · Post by **Matt F** » Mon Feb 14, 2011 11:18 am

I have heard that even though they are ATC, you have to let the sample cool a bit so it is in the range for the ATC to function properly. Since you are only using a few drops, the sample cools quite quickly but still needs a little time. I put on a few drops and then wait about 10 seconds or so to confirm the reading. I brew inside so my refractometer is always at room temp, 64 F to 72 F depending on the season.

hoboscratch · Post by **hoboscratch** » Mon Feb 14, 2011 11:28 am

My final OG sample was at pitching temp when I took it, and was indoors, so it was right at 70F when it was measured. When I noticed it was way off, I re-calibrated just to be sure, and it was still off.

Admittedly the preboil sample would have been at at least mashing temp when it was dropped onto the lens, and I discarded it without letting it sit for any real length of time.

Got this off NB, I'm going to see what sort of warranty there is on this, either with them or the manufacturer. I do have some DME, maybe I'll mix up a sample and bring some to the meeting. If someone with a refractometer wouldn't mind bringing theirs, we could compare readings.

bkanderson · Post by **bkanderson** » Mon Feb 14, 2011 5:00 pm

What brix to OG conversion are you using? I use this formula =1.000019+(0.003865613*brix)+(0.00001296425*brix)+(0.00000001128*brix)

Or maybe you don't need to convert it. I use this and it is pretty close

hoboscratch · Post by **hoboscratch** » Mon Feb 14, 2011 5:29 pm

mine has SG readings so I didn't try to convert from the Brix side. I am planning on making a few samples to test with. depending on my results, i may ask peeps to bring some refractometers to the meeting. i know its at your place, so maybe i can compare with yours too?

tompb · Post by **tompb** » Mon Feb 14, 2011 5:53 pm

I let beersmith do my conversion. I do know you can't let the refractometer sit on the patio table in the sun and expect anything close to accurate.

carrisr · Post by **carrisr** » Tue Feb 15, 2011 5:40 pm

I'll try to bring mine along.

Matt F · Post by **Matt F** » Wed Feb 16, 2011 12:21 am

Mine is just Brix too. I have a conversion chart printed and stuck on the wall above the mashtun. Nice and simple.

hoboscratch · Post by **hoboscratch** » Thu Feb 17, 2011 11:36 am

well i recalibrated it last night and tested with a couple samples. I let the distilled water and the samples sit on the lens for a couple minutes this time around. Its closer now, but it almost seems like the ATC isn't working or something. The samples are at room temp (70) and with temp adjustments my hyrdometer reads right at 1.019-1.020, and the other sample is right at 1.039-1.040. Yet my refractometer will read 1.017 and 1.037, respectively. Its definitely the ATC model, at least per the case and instructions. I dunno, I will bring my samples and refractometer along tonight. Randy if you still want to bring yours, or if anyone else is interested in comparing results, please bring yours along...

JimF · Post by **JimF** » Thu Feb 17, 2011 12:35 pm

hoboscratch wrote:well i recalibrated it last night and tested with a couple samples. I let the distilled water and the samples sit on the lens for a couple minutes this time around. Its closer now, but it almost seems like the ATC isn't working or something. The samples are at room temp (70) and with temp adjustments my hyrdometer reads right at 1.019-1.020, and the other sample is right at 1.039-1.040. Yet my refractometer will read 1.017 and 1.037, respectively. Its definitely the ATC model, at least per the case and instructions. I dunno, I will bring my samples and refractometer along tonight. Randy if you still want to bring yours, or if anyone else is interested in comparing results, please bring yours along...

Mine does BRIX and SG. I'll bring it tonight. I won't be surprised if we get as many different readings as we have refractometers...

hoboscratch · Post by **hoboscratch** » Thu Feb 17, 2011 5:47 pm

Dammit. Came home to a puking kid and a sick wife. I'm probably not gonna make the meeting, so you can leave your refractometers at home.

hoboscratch · Post by **hoboscratch** » Mon Mar 14, 2011 9:14 am

So as a followup, I've done some more testing with this. What I've found is that my refractometer, even tho its calibrated at room temp with distilled water, reads lower than my hydrometer, which reads spot on at 0 when adjusted for temp with distilled water. By about 2 points or so but its pretty much across the board, at any gravity I've tested with. So if someone still wants to bring a refractometer to the meeting tonight to compare, I've got a sample of 1.040 wort to test with.

Matt F · Post by **Matt F** » Mon Mar 14, 2011 9:34 am

I have a refractometer we can use if folks would like to play. I have found similar differences but haven't done as much testing. I still take a hydrometer sample as well as refractometer reading for SG and FG. I have some distilled water sitting around the brewery.