barry wrote:the purpose of measuring the water temp after it exits the showerscreen and before it enters the coffee is that is the point where the influence of additional variables is minimized, and we can speak with some confidence. it is the zero point of the brew cycle. if the tc is inside the puck, then the measured temperature depends upon the temperature of the grounds at the moment the brew cycle stas, which is a function of how long the portafilter is in the group before brewing, what the ambient temperature is, and how much heat was generated by grinding, and how much time has elapsed between grinding and the entry of the portafilter into the group. plus, the mass of the puck will attenuate any fluctuations in brew water temperature.

someplace I have a portafilter that has three thermocouples in the basket, plus a few more around the outside... one of the perils of an 8-channel datalogger and a roll of tc wire.

we did loads of measurement tests in the years leading up to the Scace Device.

as an aside, my daughter was drinking some coffee the other day from a demitasse... "daddy, why is there a hole in the side of the cup?" "because I drilled one there." "why?" "so I could put a thermocouple in it to measure how quickly the cup would heat up and cool down." "oh."