so you got the same relatively flat-lined curve with the tc as with the thermofilter?HB wrote:I also did that to calibrate the two to each other (i.e., set the one's offset so the delta is zero).
--barry "go page 6!"
so you got the same relatively flat-lined curve with the tc as with the thermofilter?HB wrote:I also did that to calibrate the two to each other (i.e., set the one's offset so the delta is zero).
I adjusted the offset of the two inputs such that T1-T2=0. During the initial two-thirds of the shot, the delta display reading jumped erratically, I presume because the unattached TC was jiggling as the system pressurized. Once the temperature was at its peak, the T1-T2 value hovered around zero.barry wrote:so you got the same relatively flat-lined curve with the tc as with the thermofilter?
Would you post a closeup picture of your TC portafilter without coffee? Judging from the two charts, it looks like yours tracks closer to the thermofilter's results than the over the lip approach.BobY wrote:I did some comparison testing with a portafilter I assembled some months ago, with an embedded TC whose junction just reaches the very upper-most surface of the coffee puck.
To give readers a perspective on just how much placement makes a difference, see the chart below:gscace wrote:What about all of those other profiles that you haven't measured? Bury the thermocouple 5mm down inside the cake and you'll get a completely different profile. What is the correct profile there?
But Jim, suppose you are trying to set up multiple machines to produce the same result with the same coffee, as in a coffee service supplying multiple shops. Or suppose your machine breaks and you need a replacement of the same type? Do you believe a fairly crappy pressure gauge whose history is unknown, or do you just get the temperature directly?another_jim wrote:The second issue is the relation between shot taste and precise temperature measurement of any kind.
Here I'm a sceptic. I fully believe in raising the temperature of sour and lowering the temperature of bitter shots, but this is not anything for which one needs accurate thermometry -- one doesn't need to know the absolute temperature, just have some serviceable way of lowering and raising it reliably.
For instance, I don't think taste to temperature relations are repeatable across different kinds of machines. And on the same machine, the hot:cold::bitter:sour relation seems to change for ristretto and lungo shots, although this could be because of the changed temperature curve during the longer ristretto shots.
That's a very good point. For a shop using identical brand machines, I would agree that excellent setup instrumentation is the way to go if one is to have any prayer of getting a high quality product for all.gscace wrote:But Jim, suppose you are trying to set up multiple machines to produce the same result with the same coffee, as in a coffee service supplying multiple shops. Or suppose your machine breaks and you need a replacement of the same type? Do you believe a fairly crappy pressure gauge whose history is unknown, or do you just get the temperature directly?
Although Dan found no difference in his blind test; I keep being struck with how differently the same coffees come out when brewed on an E61 and the LM with brew pressures and temperatures set quite closely (using the conventional in-basket TCs). The Peppina and Silvia had other taste profiles again, although here the pressures were not be the same.WRT different machines and different temps - I'm not so sure I buy into that. Most 58mm pf machines use pfs with very similar dimensions. They use similar, if not identical, pumps. As far as flowrate and pressure buildup goes I'd say that the flowrates are pretty much identical and the buildups may not be. But there are enough similarities that saying temperature is not transferrable is a pretty hard sell. My experience is that it is transferrable.
Now the business of shot volume is very interesting and opens up a good can of worms. As was shown here graphically, spatial temperature profile is gonna be volume flow rate dependent. So if you brew ristrettos you may need something different from lungos. But once again, in order to do it well, you'll be striving for consistency and once again quantifying boundary conditions makes it possible to transfer to other machines more easily.