I replaced the brew boiler temp sensor on my Vivaldi and want to check the offset. In the past, before even hearing about the Scace device, I used to put a hole in a single-basket, insert a fast response TC to about the midpoint of the puck, and waste a little coffee to check temp during brewing. Do you think this is a reasonable technique? Thanks again for all the advice. (and some great coffee recommendations!)

I think it is one of the best techniques...

Thanks Dan and Dennis. It has been kind of interesting. My initial measurements were made without control of the flow rate (using foam instead of coffee) and wow, what a difference-- a quick spike in temp and then decrease. While I should have guessed the importance of flow rate, observing it first hand is pretty dramatic. When I added coffee to get a reasonable flow rate temperature stabilized nicely. Luckily, I checked my TC with boiling water (at my elevation and barometric pressure) and found it to be off about 1 C, so adjusted accordingly. A Scace thermofilter would be fun, but pretty rare for the Vivaldi 53mm size.

The problem with packing the basket with coffee and having the TC run up through or over the lip of the basket above the puck is that you will be reading the coffee puck temperature and not the water temperature. It will get you close and you can see what the general temperature profile of the machine is but do not rely on it for any kind of temperature adjustments. What you get from the coffee packed basket with a TC in it will be several degrees low most of the time.

cannonfodder wrote:The problem with packing the basket with coffee and having the TC run up through or over the lip of the basket above the puck is that you will be reading the coffee puck temperature and not the water temperature.

I disagree, not true. I did enough testing to know this not to be case. When thermocouple head is positioned almost on top of the basket it will always stick out and you will be reading the water temperature... You can rely on it 100%.

Exactly my thinking. And the exact temperature is really tricky and pointless to find out. Who knows where people exactly measure these and when? On top of the puck, in the middle at the bottom? All this measuring does is get you in the range so you can adjust by taste from there. And it can give you picture into the temperature profile of the machine. But that's all it is....

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 starts, 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."