alestateyall
Well-Known Member
I have a new ATC refractometer with % brix and SG scales.
My question: Should I calibrate it each day I use it?
The manual for the refractometer says to calibrate it at 20C (68F). My house is 75-80F in the summer so there is no good way to get the refractometer to 68F.
This weekend I had the following experience.
1) refractometer stored throughout brewday in shade in doors in my kitchen.
2) read refractometer with distilled water. Reading was above zero.
3) dial screw to move reading to zero. Was this the right thing to do or was the reading above zero the ATC doing its job and I actually moved the refractometer out of calibration?
4) OG: refractometer = 12.8 brix (1.052 SG), corrected hydrometer 1.053 SG* I had the same experience with pre-boil gravity readings but I don't remember the numbers.
I repeated steps 2-4 many times that day. I waited varying times between placing sample on the glass and reading the refractometer. I generally waited 30 seconds to 2 minutes.
I know the difference is not much but the refractometer reading is before wort correction factor. I was supposed to divide the refractometer reading by 1.02-1.04 wort correction factor) before converting to SG since the refractometer measures sucrose content not maltose content. Based upon these common wort correction factor values I was expecting the refractometer to always be higher than the hydrometer. So I was expecting a refractometer reading of 13-13.3 brix (pre wort correction factor). That is pretty far from the actual reading and outside of the stated error of +/- 0.2 brix for the refractometer.
* I have previously (months ago) measured hydrometer with distilled water at 60F. The hydrometer was 1 point high. I subtract 1 point from the reading before temp adjustment.
I have since calibrated the refractometer after sitting in a 68F environment for 30 minutes. So my question is should I leave it alone if the reading is not 0 from distilled water next time I use it on a brew day?
Thanks!
My question: Should I calibrate it each day I use it?
The manual for the refractometer says to calibrate it at 20C (68F). My house is 75-80F in the summer so there is no good way to get the refractometer to 68F.
This weekend I had the following experience.
1) refractometer stored throughout brewday in shade in doors in my kitchen.
2) read refractometer with distilled water. Reading was above zero.
3) dial screw to move reading to zero. Was this the right thing to do or was the reading above zero the ATC doing its job and I actually moved the refractometer out of calibration?
4) OG: refractometer = 12.8 brix (1.052 SG), corrected hydrometer 1.053 SG* I had the same experience with pre-boil gravity readings but I don't remember the numbers.
I repeated steps 2-4 many times that day. I waited varying times between placing sample on the glass and reading the refractometer. I generally waited 30 seconds to 2 minutes.
I know the difference is not much but the refractometer reading is before wort correction factor. I was supposed to divide the refractometer reading by 1.02-1.04 wort correction factor) before converting to SG since the refractometer measures sucrose content not maltose content. Based upon these common wort correction factor values I was expecting the refractometer to always be higher than the hydrometer. So I was expecting a refractometer reading of 13-13.3 brix (pre wort correction factor). That is pretty far from the actual reading and outside of the stated error of +/- 0.2 brix for the refractometer.
* I have previously (months ago) measured hydrometer with distilled water at 60F. The hydrometer was 1 point high. I subtract 1 point from the reading before temp adjustment.
I have since calibrated the refractometer after sitting in a 68F environment for 30 minutes. So my question is should I leave it alone if the reading is not 0 from distilled water next time I use it on a brew day?
Thanks!