I agree regarding the Thermal and cold weather. It took me awhile to figure out the problem and it was quite frustrating to arrive at the job site on mornings when the temp was around 40 degrees F and see my micron reading was worse than it was the previous afternoon.
I've been using the Yellow Jacket digital that indicates zero to atmospheric for a few years now and so have several co-workers. I never heard of the Bluvac until just now. I will admit if you put half a dozen Yellow Jackets on the same system, they all give a different reading until you get close to the desired vacuum level.
take a minute and read the Thermal manual, there is "secret" cold weather calibration ritual
I have used my Thermal in well bellow freezing weather with no problems.