Calibrating a YiHua 939D

[cook]

I cannot figure out how to the calibration should work on my YiHua 939D. I thought it would have a dial that you could turn to raise or lower the temperature so it matched the display, but it has a push button. I have not tried it since I did not want to get it out of calibration with no way to get it back. I have searched the 'net multiple times but don't see anything about how to calibrate it.

Does anyone know what the right procedure is for calibrating it?

[diif]

It doesn't need calibrating. There will always be a difference between the shown temperature which is the thermocouple and the tip which isn't completely in contact with the heating element. The actual temperature does not matter just the value at which it melts solder.

[cook]

diff,
Yes, you are definitely right, no question about that. But.... Since it does have a calibration button on it, I'd like to know how it works. Curiosity is a curse... and a blessing.

[diif]

You'll need a HAKKO FG-100 or a clone or similar to measure the temperature at the tip.