Well, the people at work were curious today about the Thermocrons out in the butterfly garden, so in between watching caterpillars molt to chrysalises, I went out and fetched the monitors in for reading (and found a nice fat 5th instar in the garden!).
It appears that the low monitor is seeing a wider swing of temperatures, by about 2 degrees, than the high monitor (eg cooler at night and hotter by day). But running the data in the Degree Day worksheet, they both come out very similar- for the past 7 days, I have accumulated 142.95 mDD on the high thermocron and 141.79 mDD for the low.
I'll download from my home monitors tonight and see how they have fared. I hope someone else can share their results too!