What's More Accurate?

[smangold]

What is more accurate? A Fermometer or a Johnson Controller, with the sensor taped to a glass carboy.

I ask because I'm getting two different readings on my carboy. My Johnson Controller is reading 73 degrees and the Fermometer is reading 78 degrees.

I should note that I have a piece of foam insulation covering the sensor as to not allow the air in my fridge to interfere with the reading. I also have a fermwrap taped to the carboy. It is on the opposite side of the Fermometer. I guess the glass could be absorbing the heat and throwing off the Fermometer. But why not the Johnson Controller?

 

[matt2778]

From what I understand the stick on fermometers are accurate to within a half degree of wort temp. I've found similar discrepancies with regard to controller temp and wort temp, however I've not made any attempts to insulate the controller probe or attach it to the fermenter. Most of my fermentations average 5 or 6 degrees higher than the controller with the exception of some of the more violent Belgian strains.

 

[smangold]

Most of my fermentations average 5 or 6 degrees higher than the controller with the exception of some of the more violent Belgian strains.

This may explain why my fermentation fridge smells like banana so much (I'm using Wyeast 1214 in a Belgian Honey Ale). I really didn't pay attention to the fermometer until about 5 days into the fermentation.