Although I don't have a BDB, I can chime in with my volumetric dosing experience on my NS Musica. The volumetric dosing was inaccurate and too many variables must stay consistent in order to get consistent results. At the end, just like Randy, I just gave up and went with the manual mode. In general I find volumetric dosing to be mostly inaccurate in general (my experience). On weekends, I have the privilege of working on commercial machines owned by a coffee catering company I do some work for and both La Pavoni and the Magister I use have volumetric dosing and both are inaccurate.

Thanks all.
I have found that I can usually get consistent results when I weigh the output and set the time accordingly. After a few days, due to changes that we have already talked about, I have to change dose or grind. I am just weighing output every couple of days to make sure I haven't strayed too far off target.

Timed output for now. Too bad this feature doesn't work.

lancealot wrote:Thanks all.
I have found that I can usually get consistent results when I weigh the output and set the time accordingly. After a few days, due to changes that we have already talked about, I have to change dose or grind. I am just weighing output every couple of days to make sure I haven't strayed too far off target.

Timed grinding for now. Too bad this feature doesn't work.

In a perfect world the feature should work in a way that if you set it to give you 36 gm in the cup (output) based on 18 gm of coffee (input) as an example then that's what you always get regardless of the situation and only timing will change. if coffee is stale then you get it in 25 seconds as an example, if it's too fresh then maybe 34 seconds etc.

Yes thecoffeefield, that is the way I understand it should work from the plumbing of the flow meters and a general understanding of coffee physics. But alas, it sounds like it doesn't quite work that way for many of us. Perhaps I should put a call in to the good folks at Breville customer support.

Give it a shot, I'm interested to know what they have to say about this or if they can explain how the feature works.

I guess there must be a good reason why they don't put the flowmeter in the circuit down stream from the pump and over-pressure valve ? That's how my machine works and it seems to deliver consistent doses (although it has a rotary pump, so the over-pressure is built into it).

Clearly I'm missing something here.....

Brett wrote:They still need the flow measurements where they have them, for boiler filling, etc.

For posterity, the situation stated above is not correct. The boilers have sensors in them that tell the pumps when to kick on and off according to the level of water. The flow meters shouldn't have anything to do with it. I haven't seen a wiring diagram or tested it to make sure my theory is right but as far as I can tell, this is a general operating principle for many machines. No flow meter needed to fill the boilers or keep them filled.

keepitsimple wrote:there must be a good reason why they don't put the flowmeter in the circuit down stream from the pump and over-pressure valve ?

Yes there is, I haven't priced them, but flow meters that can operate at high pressure are much more expensive then the low pressure ones used in these places on the BDB. It seems they are keeping prices down by sacrificing the proper operating performance of an advertised feature!

Since my BDB isn't used in a busy shop environment, where it might be a worthwhile compromise to automate some processes that are better done by hand, I do NOT use the volumetric capability. For making just two to six shots a day at home, it's just not worth the compromise. Any compromise.

I know it's fun to watch the pro baristas in the shop you like. And if ritual is what you like about espresso, then you have an argument to imitate them. But if taste is why you are into espresso, you have the luxury of NOT having to take the kind of shortcuts they might take in a busy shop. For two to six shots a day, there is simply no reason NOT to weigh every dose and extraction, and RDT and WDT every puck prep. The legends on here do it. So should you, if taste is the main reason for your interest in espresso.

-Peter

Yeah, I get it. This doesn't answer my question but I get it.

I was just hoping to learn if I could make my machine work as advertised.

Did you not feel that the previous posts did a pretty good job of summing up the system used by the BDB, and it's strengths and weaknesses? I did. And I assumed you did, too. Apologies if I assumed incorrectly.

I should also add that in the top-notch shops, where they are using machines with the more expensive and precise volumetrics, if they are using the volumetric capability at all, the conscientious barista will pull and taste sample shots from time to time and make tweaks to the grind and the volumetrics. So even the best equipment money can buy needs tweaking throughout a shift.

-Peter