Scace Thermofilter Temperature Device - Page 10

by **Abe Carmeli** on Wed Aug 31, 2005 11:03 pm

barry wrote:i just went back and reread the entire thread. the only point i can see which might have lead to the confusion was when you used the phrase "measuring a real shot". i took that as you wanted the thermofilter to mimic the thermal performance of pulling a shot through coffee. what i think you might have meant, and what i didn't get until now, was you want the results from the thermofilter readings to better duplicate the results you get from using a tc on top of the puck during a real shot.

We finally understand each other, and thanks for taking the pains to re-read that long thread. This is my take on it: The T/C over a coffee puck is flawed indeed, because of the flimsy placement in the puck, mostly. However, it does have at least one advantage over the simulated shot with the thermofilter: The coffee puck is cold. I suspect that the narrow range in variation in temperature within a shot is not due to faulty reading by the T/C, but mostly due to that difference. In that regard, it is reporting a more accurate behavior during a shot than the Thermofilter.

Now, how does this help me at all? In what way is the T/C reading better for my espresso? It all boils down to what I'm trying to measure. If I use a dual boiler machine for example & set temp tp 202f, and test it, the T/C method is likely to be more accurate in showing real brew temperarture. I will need to do It a few times and average the results because of the possibility of error in measurement, but it will be closer to real brew temperature.

The argument that I hear from you, and Dan, is that it does not really matter. What you are testing here is consistency. The scale can be adjusted to whatever you want. It is true, but only if everyone uses this device. For the greater community that still uses the T/C method, there is no standard to communicate with. Having a way to translate one to the other, keeps everyone happy. Hence my quest for the formula. When a roaster tell you that the optimal brew temperature for his/her beans is 203 degrees, we want all to be on the same page.

by **barry** on Wed Aug 31, 2005 11:22 pm

Abe Carmeli wrote: a dual boiler machine for example & set temp tp 202f, and test it, the T/C method is likely to be more accurate in showing real brew temperarture.

no, it's not, for all the reasons previously mentioned. too many variables, the least of which is the tc placement.

It is true, but only if everyone uses this device. For the greater community that still uses the T/C method, there is no standard to communicate with. Having a way to translate one to the other, keeps everyone happy. Hence my quest for the formula. When a roaster tell you that the optimal brew temperature for his/her beans is 203 degrees, we want all to be on the same page.

unfortunately, without a standardized test procedure and equipment, the numbers don't necessarily translate. that was the major force behind the development of the thermofilter. numbers from my tests with my tcs are just the vaguest relative reference points for others. same with roaster temps, btw. just because i drop dsb at 438F doesn't mean that's the "correct" temperature for every other roaster. it might not even be an accurate temperature because of cumulative systemic inaccuracies. another issue is differences between machines, both machine types as well as unit to unit variations.

and, in the end, the "correct" temperature is that at which the coffee tastes the best, and it wouldn't surprise me if that varied from machine to machine (especially type to type, and model to model).

if i tell you that i like DSB at 195F, and you do your tc/puck measurement and come close, then decide that you like it better at 197F, then neither of us is wrong or inaccurate.

by HB on Wed Aug 31, 2005 11:31 pm

This is a very good discussion and now I think we're understanding each other's viewpoint (perhaps not agreeing, but understanding). To give a concrete example of the effects under discussion, tonight I did a series of thermofilter versus over-the-lip comparisons:

Thermofilter setup: Warmed up in the group for over an hour. Pulled a series of shots with various intervals from twenty seconds to several minutes as part of my flushing fine tuning study. I noted the maximum temperature for each shot. When I was satisfied that my technique would give me a variance shot-to-shot of less than one degree, I recorded the next two pulls. They were essentially identical, the plot above is the first one of two recorded.

Over the lip (TC) setup: Getting reliable data proved tricky for a couple reasons. First, I needed to place the TC wire across the puck and lock in very quickly, since the A3 requires a "flush and go" approach for optimal temperature stability (i.e., the rebound time is around five seconds tops). Consequently the initial spike is likely higher than in normal usage. In addition, to speed up the placement without burning my fingers, I used cold baskets, which would further perturb the natural shape of the curve.

The latter setup problems do once again underscore one point we all agree on: It's a lot easier and more repeatable to use a fixed position TC. If I were planning a long series of measurements, I would instead route the thin TC wire under the gasket and wrap it around the dispersion screw. My apologies, I didn't think to do that before the machine was very hot.

Interpretation: With the caveat above in mind, note the red line shows the traditional declining curve one would expect to see for an HX machine. The thermofilter starts out already heated, hence its high initial temperature of 190.7F. The effect of the cold basket and cool coffee is pretty obvious since the starting temperature is 176.7F; generally the first measurement using hot baskets is closer to 185F mere seconds after the portafilter is locked in. Despite the less than ideal conditions of my test, Abe's point is plainly evident: The true shape of the temperature profile is quite different than that depicted by the thermofilter. Barry would counter that it's intentionally so since the device's purpose is to measure the boiler's performance, not the system dynamic that includes unpredictable elements like genuine coffee pucks.

Speaking of standards: Greg sent me a copy of the thermofilter instructions and the WBC protocol for its use. I converted it to post-able format and returned it to him for his verification. He should be posting it shortly so we'll all be able to work from the same instructions.

by **Abe Carmeli** on Wed Aug 31, 2005 11:44 pm

HB wrote:Interpretation: With the caveat above in mind, note the red line shows the traditional declining curve one would expect to see for an HX machine. The thermofilter starts out already heated, hence its high initial temperature of 190.7F. The effect of the cold basket and cool coffee is pretty obvious since the starting temperature is 176.7F; generally the first measurement for hot baskets is closer to 185F mere seconds after the portafilter is locked in. Despite the less than ideal conditions of my test, Abe's point is plainly evident: The true shape of the temperature profile is quite different than that depicted by the thermofilter. Barry would counter that it's intentionally so since the device's purpose is to measure the boiler's performance, not the system dynamic that includes unpredictable elements like genuine coffee pucks.

This is an excellent illustration of the principles at play. Nice graph Dan.

by **barry** on Wed Aug 31, 2005 11:54 pm

HB wrote:Abe's point is plainly evident: The true shape of the temperature profile is quite different than that depicted by the thermofilter. Barry would counter that it's intentionally so since the device's purpose is to measure the boiler's performance, not the system dynamic that includes unpredictable elements like genuine coffee pucks.

nope. read your comments about the curves and it might jump out at you.

"note the red line shows the traditional declining curve one would expect to see for an HX machine."

Q: why is this the "traditional" curve, and why would you expect it?
A: possibly because it is a curve generated with <however mildly> flawed methods, and you expect to see it because you've seen it so many times before.

my counter is that it is entirely possible that the actual brew water profile is better represented by the upper curve, and the "traditional" curve is a result of measurement artifacts.

in other words, perhaps we need to re-think our assumptions about machine performance.

--barry "stepping out of the cave is never easy"

by HB on Thu Sep 01, 2005 12:03 am

Barry, you may well be right. My assumption is that HX machines have an initial spike that I nickname the "HX hump". But that assumption relies on intuition and measurement techniques that could be fatally flawed. Nonetheless, the two curves above are reproducible at will, so whatever the cause may be, there is a difference afoot. The next question is then: Should I care?

By the way, if anyone is interested... I did sip a teenie bit of the last shot. It was good.

by **barry** on Thu Sep 01, 2005 12:12 am

HB wrote:Nonetheless, the two curves above are reproducible at will, so whatever the cause may be, there is a difference afoot. The next question is then: Should I care?

yes, if the flaw is repeated, then the curve will be reproducible. and yes, you should care, because understanding of how the machine really works depends upon it. just think, the hx guys might have been able to do schomeresque quality flat-line brew temps all along. :lol:

btw, here's a test for you: put the tc over the rim of the thermofilter!

--barry "naaahhhh... couldn't be!"

by **Abe Carmeli** on Thu Sep 01, 2005 12:18 am

barry wrote:
btw, here's a test for you: put the tc over the rim of the thermofilter!

--barry "naaahhhh... couldn't be!"

I actually did that a week ago. The T/C over the lip reported the same temperature as the Thermofilter probe. The problem is not in the T/C reading but in the difference that the coffee puck makes, as I have already stated. Back to my original point.

This may raise a different question: should we measure brew temperature with or without coffee?

by HB on Thu Sep 01, 2005 12:20 am

I also did that to calibrate the two to each other (i.e., set the one's offset so the delta is zero). Nothing usual jumped out at me. OK, I'll guess that Barry's referring to the jumpiness of the TC's initial readings. Did I win?

by **barry** on Thu Sep 01, 2005 12:33 am

Abe Carmeli wrote:This may raise a different question: should we measure brew temperature with or without coffee?

i thought we answered that already.


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