Ca

weebit_nutty wrote:That's a great thread. Thank you for the reference. I will read through it when I get a chance. I do think the conversation here has developed into something a little different. This is not just about flow rate, normally used in volumetric application and pressure profiling. Here, both optimal brew pressure *and* extraction rate can be maintained, at least in the case of a slightly loose grind. The exciting prospect here is potentially untying (or should I say 'loosening') the stringent relationship brew pressure has on extraction rate.

Not sure you can have it both ways. If you have a pressure applied on the puck, the flow rate will be determined by the puck density and resistance to flow.

If you limit the flow to the puck then the puck will dissipate the pressure and the pressure will drop.

Flow limiting is really only for filling up the area above the puck in a controlled manner.

The idea weebit is going for is basically a variable pressure basket. The result may not end up as desired, but I think it would be fun to experiment.

I have actually done quite a bit of work on flow profiling. It is very similar to pressure profiling in most circumstances. During the initial fill there is zero pressure so either system works similar. During extraction the two systems are also similar since there is almost a direct relationship to pressure and flow rate. This fails however when you try to over pressure the coffee and the flow rate can sometimes become less. I have not yet had a great enough difference between the 2 systems that would make me choose one over the other based upon taste in the cup. However with the new flowmeters coming out it could eliminate the need for an expensive pressure sensor. The current flow meters are not consistent to use for flow profiling. Your results can vary as much as 30%. Most flow meters are reasonable accurate at one flow rate. Since the flow rate for espresso is not constant they add quite a bit of error. Overall for the entire shot they can be OK but the readings "intrashot" and not great.


BillC

weebit_nutty wrote:You are right.. But I see a difference, too. If flow is measured and controlled at the outlet of hte brew chamber (ie, the spout), brew pressure can actually be maintained for any grind. It could very well be the most forgiving method of espresso extraction, as you now directly taking full control of the brewing/extraction. We can be free from having to tie the grind size to the extraction rate. Or at the mercy of roast quality. And yes, I do recognize if you use crappy beans or crappy grounds, will still taste like crap. But I think it eliminates the utter precision needed in making really good espresso. Espresso is a freaking merciless balancing act! .

I am pretty sure that the logical conclusion to this train of thought has already been invented and employed. Pressurized portafilters.

Maybe just for fun, try one out on a machine that isnt ridiculously low quality

day wrote:I am pretty sure that the logical conclusion to this train of thought has already been invented and employed. Pressurized portafilters.

Maybe just for fun, try one out on a machine that isnt ridiculously low quality

Kind of... Pressurized baskets however have a fixed opening and are for folks you use supermarket beans. For proper espresso, with a dynamically adjusting flow valve it would operate only as required, closing only as much as needed for the correction. A perfectly dialed basket would have a zero correction, a completely open valve, whereas if the shot would be only slightly loose, the correction would just as slight, allowing the puck to take up the majority of the resistance in the extraction. I dunno it just sounds interesting. I might just give this a try.. Any ideas what exact off the shelf parts I might need to cobble this experiment together?

Billc wrote:The current flow meters are not consistent to use for flow profiling. Your results can vary as much as 30%. Most flow meters are reasonable accurate at one flow rate. Since the flow rate for espresso is not constant they add quite a bit of error. Overall for the entire shot they can be OK but the readings "intrashot" and not great.


BillC

That's too bad. Perhaps an alternate method for quantifying the extraction rate could be used. How about employing load cell for quantify the extraction rate, hence the flow rate could be an entirely independent operation from the pump. The pressure transducer could be used to operate the pump to maintain the proper brew pressure. Imagine it'd be kind of weird to tare your cup before pulling your shot.. Oh wait, I know a few folks on here who do this already!

I tried the same with a Gicar flowmeter. The specs are wonderful, reality - a different matter. More in the following thread.

Gicar flowmeter accuracy

With all the developments over the last decade to control certain variables during extraction, I'm quite surprised that there hasn't been a drive towards the simplification/automation of measuring and verifying the final product. I don't count gravitometrics since that is still an indirect way to measure the true product. With my background, I'm a deep believer in the simplification of processes to gain a predictable result, but first and foremost the result must be easily measured and defined.

My dream setup would rely heavily on the portafilter.
- Has contacts on the ears that provides electricity and completes a connection for data transmission between the portafilter and the machine.
- Measures the weight of the grounds contained
- Contains a TDS sensor at the exit to measure product.

The desired TDS level would be set by the end user and the measurements taken during extraction will control pressure/flow in real time. Once a minimum threshold is crossed, the extraction process is terminated to prevent over-extraction.

If I don't come up with the setup first, I will be more than happy to throw a fistful of cash towards the person that does.

It's a bit late in the chain, but one could in theory use the bluetooth connection from a Lunar to get some of the information. Delta weight/time is flow and quite accurate for what it is, jut a bit time shifted.

Ira