Proper Temperature

[gmc8757]

Hello, first time boiling with an evaporator.
I have a dial thermometer that reads one temp, then I have the auto draw I made with the temp controller and temp probe reading another temp. Can you calibrate your auto draws?
I put the probe in boiling water and it was reading about 202. I calibrated the dial thermometer to read 212 in that same boiling water.

My 2x4 mason pan has a 1/2 ntp fitting I just screwed the temp probe in. I may put the dial thermometer there and drop the probe in over the side.

How can I be sure I'm getting a good temp reading? I do check it with a hydrometer but it would be nice to have an accurate temp reading I can watch. Thanks guys..I enjoy reading through the site...

[Cedar Eater]

Hello, first time boiling with an evaporator.
I have a dial thermometer that reads one temp, then I have the auto draw I made with the temp controller and temp probe reading another temp. Can you calibrate your auto draws?
I put the probe in boiling water and it was reading about 202. I calibrated the dial thermometer to read 212 in that same boiling water.

My 2x4 mason pan has a 1/2 ntp fitting I just screwed the temp probe in. I may put the dial thermometer there and drop the probe in over the side.

How can I be sure I'm getting a good temp reading? I do check it with a hydrometer but it would be nice to have an accurate temp reading I can watch. Thanks guys..I enjoy reading through the site...

Compare the reading of the dial thermometer to the reading of the temp probe controller/thermometer at the draw off when the sap is boiling, then move the dial thermometer back to the boiling water, make sure it returns to 212, go back to the draw off and compare again, and repeat again. Average the three comparisons. That average will be the offset. You can either adjust the probe thermometer so that the offset is zero, or you can just remember to add or subtract the offset from the reading on the probe temp controller where you want the draw off to occur.

[gmc8757]

Thank you. I will give that a shot. So basically...
1) keep probe and dial in boiling sap...mark down both readings
2) leave the probe in the sap, but take the dial out and put it in boiling water. Make sure dial reads 212
3) put dial back in boiling sap and mark both readings again
Repeat 3 times and average out the difference in temps. use that as the offset.

I see in the temp controller where I can add the offset, so that may work just fine.
Thanks again

[Urban Sugarmaker]

I calibrated my RTD probe in boiling distilled water. If you are really particular about it you can go to http://www.virtualweberbullet.com/boilingpoint.html and get a barometric correction for boiling point at the moment you boil. It's the best calculator I have found and I like it because it takes the reported barometer measurement and un-corrects it to sea level. When I started with raw sap in the whole pan this season, my probe was right on the money with the calculated boiling point that day. You also have to remember that a calibrated RTD is far more accurate than a bimetal dial thermometer (at least that's what I have read).

Cedar Eater has a good point with averages too. I did not do that but found that the measurement was steady.

Lastly, when I was checking the syrup with a hydrometer I had to make small adjustments to the draw off temp. For some reason I was not getting syrup at exactly 7.1 above the calculated boiling point, but there's probably other variables I did not account for.

[Cedar Eater]

Thank you. I will give that a shot. So basically...
1) keep probe and dial in boiling sap...mark down both readings
2) leave the probe in the sap, but take the dial out and put it in boiling water. Make sure dial reads 212
3) put dial back in boiling sap and mark both readings again
Repeat 3 times and average out the difference in temps. use that as the offset.

I see in the temp controller where I can add the offset, so that may work just fine.
Thanks again

Yup, you got it. The point of averaging is to take out inconsistencies in the dial thermometer. If the three differences are close, you have a good dial thermometer. If they're not close, chuck it and get an instant read digital thermometer, or get used to taking multiple readings and averaging them.

[gmc8757]

That's excellent, thank you both. I did that and seem to be on the right track now. My only issue now is where to put the probe. I first tried to put a 4 inch probe in the threaded female on the bottom of the pan - this is about 6 inches from where it draws off. On my first boil, I boiled down to where the sweet was below the probe (I kept a good eye on it and it didn't get too low) so the probe wasn't getting a good reading. Then I put a dial thermometer in that spot and got a 6 inch probe to stick down from over the side. I put the tip extremely close to the bottom of the pan, got boiling, and wasn't getting a good reading - I guess there wasn't enough sticking in the sweet. So I finally just laid the 6 inch probe angled down and got a good amount of it in the sweet - I was getting a good reading this way.

I have to figure out if I want to keep the dial in that threaded spot or put a probe back.