Questions about temperature controller

I just bought myself a Johnson A19AAT-2C temperature controller for a chest freezer, and I have a couple of questions about it.

How accurate is this device? I have an old freezer thermometer in the freezer and it shows a temperature colder than what I have set on the controller. It's outside the differential by a few degrees. I suspect it's the thermometer that's off, but I can't be sure until I get another thermometer.

What's the best way to position the probe in the freezer? Should it be at the bottom, attached to the side, or even in a container of water?

I use the same one and have never had a reason to not trust it.

Start by placing the probe in the same location as your thermometer. I hang mine so the probe is just under the halfway point in my keezer and it works good for me.

You can buy 6 thermometers and get "at least" 6 different readings. It is also very specific to location and liquid immersion.

I recommend using a thermalwell or something like it so you can put the thermometer right in the liquid, that is you closest and most stable temperature.

After that, good old gut level approximation is all you need.

That controller has a 4 degree variance. If you put the probe in liquid you are going to have more dramatic temperature swings and almost guarantee 4 degrees swings in your beer temp. By having the probe monitor the air temp, it will go through more and shorter cycles as the air fluctuates 4 degrees while your liquid temp remains fairly consistent.

BendBrewer said:

Start by placing the probe in the same location as your thermometer. I hang mine so the probe is just under the halfway point in my keezer and it works good for me.

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OK. That's what I've done. Now I just need to wait for my beer