Omega has a cheaper (and deservedly so, I'm afraid to say) datalogger, the HH506RA, which comes with poor quality downloading software that *works*, and the whole package costs about the same as the Fluke software alone. I decided to buy one because I collect data from my roaster and my espresso machines regularly and typing the numbers in just sets off my tennis elbow (I don't play tennis, but I got it anyway).
I decided to do 5 separate "walk up shots" on my PID'd Cimbali Junior D1 rotary machine, 3 years old, modified with the aforementioned PID and a delay timer that allows 3+ bar preinfusion followed by a full pressure (9 bar) extraction. My machine can froth enough milk for a cappuccino in about 8 seconds but I decided to set up the experiment with 15 seconds of frothing as some may be slower and/or want to froth more milk.

This graph was obtained by flushing the group 50ml (my standard and programmed flush), then pulling a 30 second simulated shot with the Scace Device and Omega HH506RA datalogger. At the midpoint, 15 seconds into the shots, I opened up the steam valve all the way, and left it open for the remainder of the shot. Each shot was separated by more than 10 minutes, up to an hour and a half in one case.

What you see here is essentially no impact at all of frothing on shot temperature on any of the five datalogged shots. I don't believe that this finding comes from the presence of the PID in this machine, rather I think it is the inherent design of Cimbali heat exchanger machines. How transferable this information is to other heat exchanger designs made by other manufacturers, I do not know, and hope that others will test.
ken
p.s. this is cross-posted on alt.coffee; please don't respond in both threads