Outside Vs inside stack thermometer...

Are they calibrated differently? If my outside stack ther is reading 300 degrees F, what does that really mean?

I mean the mfg says to run between 250 and 500. Is that internal tack or external stack? I know the 2 can vary allot.

I have heard you add 50% to those external pipe thermometers. So if yours reads 300, your internal should be around 450.

You will have different readings between your stove and stove pipe. Most manufactures state operating temps from a central location on top of the stove. I think some cat-stoves may have internal thermometers so you know when to engage the catalyst.