Love Probe taped to carboy reads a little low

[JackSmith]

I recently built a fermentation chamber from a chest freezer. I posted about it here.

I have my first beer fermenting in it now. I'm finding that the temperature reading on the Love TSS2-2100 might not be quite right. For instance, the controller is reading 65.8F, but the stick-on LCD thermometer on the carboy reads 68 and, probably more importantly, my Mastercool 52224-A IR thermometer shows 67.2 at just about every spot on the carboy.

Any ideas on why the probe might not be reading right? Here's how I attached it to the carboy:

First, I taped the TS-6 probe to the carboy using blue painter's tape. It is firmly touching the carboy. Then I took a bubble-wrap bag from a computer card (video card, ethernet card, or something like that) and folded it over once, creating a roughly 5" by 4" rectangle of four-ply bubble wrap. I taped this over the probe, sealing all four edges to the carboy with duct tape to avoid air getting to the probe.

Still, it looks like the probe might be reading a little lower than the actual carboy temp. Any suggestions? How exactly do you affix your probe to your fermenter in the chamber, and how accurate is it?

Thanks!

 

[wilserbrewer]

I think your experience is accurate and typical, short of putting a thermowell in the beer, the easiest solution is just to anticipate the fermenting beer to be a tad warmer than the external probe on the Love sensor. The external temp will always likely be slightly cooler than the actual brew during fermentation.

My exprience is the same, so I am also interested in responses. I have three digital thermometers, they are usually within a degree....go figure.

 

[theredben]

When attaching temperature probes externally, I usually tape some insulation (usually reflectex but cardboard works) to the side of said vessel and wedge the probe underneath. This should get you 0.5 degress closer, but all probes will read slightly differently. That is the nature of measuring things. Pick one thermometer and base all others off of it.

 

[JackSmith]

Am I correct in that temperature is measured over the entire circumference of the probe? If so, I guess it would be impossible to get an accurate measurement without submerging it. Even insulation won't totally keep it from measuring the ambient temp, because insulation merely slows the transfer of heat; it doesn't stop it. Eventually the insulation will come to the same temperature as the air in the chamber, and thus the insulation touching the probe will affect the reading. However, the part of the probe touching the glass will read a bit higher, and the heat from the glass during the exothermic active fermentation should keep the underside of the insulation a little warmer. Still, it looks like I just have to pay attention to what it's doing over a few ferments and adjust for it moving forward. With some data, I should be able to have an offset constant I can use when setting the controller. Something like, "It's always actually 1.2-1.6F higher than the probe reads, so I should set the probe to 1.4F lower as long as the beer is churning."