I want to share my method for monitoring mash temperature more accurately and with (arguably) less hassle.
I'm in the process of developing an automated HERMS brewing rig, as a preliminary step I've created a mash monitor program which I've introduced in the thread HERE
Tonight I brewed an ESB and I used the mash monitor for the first time. Here is a picture of my hardware, a Labjack U3-HV. For sensors I'm using two zenner diodes (LM335
These are the same chips that are sold in "temperature sensors" commercially for ~$30/ea. They can be made for ~$5/ea if you are willing to do some soldiering.
Here is a shot of my display midway through the mash. As you can see I missed my target by a little bit. A potential point of error in sensing is that I had the sensors inserted into a thermowell which just sat in the mash. Since the thermowell will be installed in a SS mashtun, I didn't want to mess around fitting the thermowell into the side of the igloo cooler.
Lastly a shot of my temperary brewing setup with my new 60qt SS kettle, it rocks
Here's the raw data