Those probes are tricky. The problem with them is, if you submerge them beyond the sleeve where the wire braid goes into the probe, you get water lodged in them and their calibration is done for. I went through three before I read about this little trick:
Place the probe in the oven and hang the plug-in outside the oven door. Let it 'bake' at ~250-325oF for an hour or so, thus driving out any moisture. Plug it into the control every once in awhile to see what the temperature reads. Once it's fairly consistant and near your oven's chosen temperture, take it out and check the ambient air temperature. You should be good to go!
I ended up with two probes and I do this before every other brew session, just for safety's sake. Works every time! My probes are within 1-2 degrees of each other. If one goes kaput, I have the backup. That's saved my a** a couple of brew sessions!
Give it a try before you head to Tarchet!