Dose control on the Ascaso Duo PID

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unclebarley
Posts: 4
Joined: 2 years ago

#1: Post by unclebarley »

Hello!

Just to preface, this is my first post AND by no means would I call myself a barista. I know enough to be dangerous and thus upgraded my old De'Longhi combo machine to the Ascaso Duo PID. Up until recently I have been manually pulling my shots based on 19 grams of coffee grounds to yield 38 grams of espresso; a simple 1:2 ratio. I weigh my grounds going in and the espresso coming out.

Recently I tried programming the coffee dose. The Ascaso Duo PID has a dose control function (by metered volume) and when I set my dose, I am having what I would call a large variance in the output of my shots. Example: This morning after setting the dose control on my first shot to yield the desired 38 gram shot @ 32.6 seconds, I proceed to pull a second shot that yielded 46.5 grams at the same 32.6 seconds. Is this variance in output normal? I would expect to have closer outputs on the shot by weight than the +8 gram difference.

I emailed Ascaso support and was told "While you can program it by volume, if you are weighing your shots by the program I would not be surprised by a variance of +/- 10ml." My second shot does fall within the variance suggested by the Ascaso rep, but again my question would be, is this normal?

Thanks!

klee11mtl
Posts: 123
Joined: 4 years ago

#2: Post by klee11mtl »

I would think the best you can expect is for the volumetric control on the machine to dispense the same amount of water each time. When you introduce the coffee, that doesn't necessarily mean the weight yield of your shot will be the same each time. For example if you use 18g of finely ground coffee, you will get a different yield with the same water amount if you switch to coarsely grind coffee.

As a test, you might want to consider setting the volumetric and then run 10 or so shots of just water to see how consistent the machine is.

Many folks who have volumetric control machines will still pull shots manually to get more consistency.

palica
Posts: 151
Joined: 2 years ago

#3: Post by palica »

At which pressure did you do your shots and at which pressure is your OPV set? Just wondering if the OPV opened, then the volume dispensed may be affected. BTW, I have the volumetric controler on my Dream and do not use it for inconsistency reasons :lol:

unclebarley (original poster)
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Joined: 2 years ago

#4: Post by unclebarley (original poster) »

klee11mtl wrote:For example if you use 18g of finely ground coffee, you will get a different yield with the same water amount if you switch to coarsely grind coffee.
That's where my question comes into play. I'm using the same coffee and same grind setting. I tested that with continuous shots and that's where I found the inconsitent yields, even though the coffee variable stays the same. Maybe I'll just have to go back to manual.

Thanks for the reply!

unclebarley (original poster)
Posts: 4
Joined: 2 years ago

#5: Post by unclebarley (original poster) »

palica wrote:At which pressure did you do your shots and at which pressure is your OPV set? Just wondering if the OPV opened, then the volume dispensed may be affected. BTW, I have the volumetric controler on my Dream and do not use it for inconsistency reasons :lol:
I tuned my pressure to 9 bars and the OPV is kicking in there. I had not thought about the fact that the OPV is dispensing water and that possibly more or less water dispenses on subsequent shots. Hmmmm....again, maybe I go back to manual.

Thanks for the reply!

bgnome
Posts: 185
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#6: Post by bgnome »

My old Saeco has a little plastic flowmeter between the tank and the pump. It is not very accurate at low flow rates, such as when water is flowing through a puck. Also, some of the water is being diverted out the OPV, so the volume that makes it out of the group head may be much lower than what is expected based on the reading from the flowmeter.
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klee11mtl
Posts: 123
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#7: Post by klee11mtl »

unclebarley wrote:I'm using the same coffee and same grind setting. I tested that with continuous shots and that's where I found the inconsitent yields, even though the coffee variable stays the same. Maybe I'll just have to go back to manual.
I could have articulated that better. The fine/coarse coffee statement was meant to be extreme examples to say introducing coffee is a whole set of variables on its own. Freshness, puck prep, grinder quality also get introduced making it difficult to isolate the variables. If you're concerned about how consistent the machine is at volume, you would need to measure the water as the only variable.

palica
Posts: 151
Joined: 2 years ago

#8: Post by palica »

unclebarley wrote:I tuned my pressure to 9 bars and the OPV is kicking in there. I had not thought about the fact that the OPV is dispensing water and that possibly more or less water dispenses on subsequent shots. Hmmmm....again, maybe I go back to manual.

Thanks for the reply!
Maybe you could try to take old beans, grind those coarse (so before OPV does kick in) and make a few shots to check if it is reproductible?

unclebarley (original poster)
Posts: 4
Joined: 2 years ago

#9: Post by unclebarley (original poster) »

klee11mtl wrote:I could have articulated that better. The fine/coarse coffee statement was meant to be extreme examples to say introducing coffee is a whole set of variables on its own. Freshness, puck prep, grinder quality also get introduced making it difficult to isolate the variables. If you're concerned about how consistent the machine is at volume, you would need to measure the water as the only variable.
I get what you're saying and I did run straight water through as a test. The machine was consistently sending the same volume though without coffee in the portafilter, so volume control itself is not an issue. I have been trying very hard to prep my puck consistently as well, so I'm not so sure it's that. I'm confident in my ground coffee as well. Using a Niche Zero and it grinds very well. One thing I have not watched while pulling a shot is how steady the pressure is being maintained through the process. Maybe the pressure is fluctuating during the pull and that could effect the yield. I'll experiment more this weekend and post the results.

Thanks again to all for the input!

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Jeff
Team HB
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#10: Post by Jeff »

I think bgnome hit it on the head. The flow meters are relatively poor to start with and tend to be even worse at low flow rates. Measuring at 5-10 mL/s (no coffee) is a lot easier than at around 1mL/s.

At least in my experience, going by eye (stream color and apparent "wateriness") or with a scale are good ways to control the shot ratio (depending on if ratio is an output or input for you).

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