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Question about volumetric dosing?
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germantownrob
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germantownrob
Joined: 2 Dec 2007
Posts: 2,156
Location: Philadelphia
Expertise: I love coffee

Espresso: Duetto 3, A Dead Oscar
Grinder: Vario-W, Preciso w/Esatto,...
Drip: Brazen
Roaster: Diedrich IR-1, HT B
Posted Wed Feb 22, 2012, 10:39pm
Subject: Re: Question about volumetric dosing?
 

I am speculating that commercial machines are likely to have volumetric dosing that is the high pressure meter or another form that can dependedly give correct volume under varying parameters. I wonder if the cost of these meters cost are a big jump, I feel some Bing searches coming on.

Wayne, some of my searches on CG led me to when you where looking at your currant machine, nice score!
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Stuart
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Joined: 9 Feb 2012
Posts: 113
Location: TX
Expertise: I love coffee

Espresso: Breville Dual Boiler
Grinder: Baratza Vario
Roaster: Air Crazy popper
Posted Thu Feb 23, 2012, 8:24am
Subject: Re: Question about volumetric dosing?
 

The online tech manual for the La Marzocco Linea describes a flowmeter that's directly in the high pressure, hot path:

Click Here (www.espressospecialisten.se)

It also cites calcium deposits in the flowmeter as a potential failure mode. (page 9 of the manual, "10" in the .pdf). Putting the flow meters on the low temperature, low pressure side of the pump probably helps limit this possibility.
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JasonBrandtLewis
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JasonBrandtLewis
Joined: 9 Dec 2005
Posts: 6,476
Location: Berkeley, CA
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Espresso: Elektra T1 - La Valentina -...
Grinder: Mahlkönig K30 Vario -...
Vac Pot: Yama 5-cup
Drip: CCD, Chemex
Roaster: No, no, not another...
Posted Thu Feb 23, 2012, 11:06am
Subject: Re: Question about volumetric dosing?
 

calblacksmith Said:

Well, I don't know which system I have but my shots are very consistent in volume. I have no problem with that at all, regardless of how long it take to pull a shot, I get the same volume at 1 min as I do at 25 seconds.

Posted February 22, 2012 link

+1

 
A morning without coffee is sleep . . .
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Gig103
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Joined: 12 Feb 2012
Posts: 244
Location: Arizona
Expertise: I like coffee

Espresso: Crossland CC1
Grinder: Baratza Vario
Drip: French press!
Posted Thu Feb 23, 2012, 11:38am
Subject: Re: Question about volumetric dosing?
 

germantownrob Said:

Jwoodyu (John) responded to this question via email after asking Bill Crossland this question. I did not ask Bill if I could repost his answer so I will put what I learned from his response in my words.

There are 3 main ways for a machine to do volumetric dosing.

Dosed by time
Low pressure meter before the OPV
High pressure meter which is after the OPV

Thank you John and Bill, this is exactly the info I was after!

Seems like the high pressure meter would be the only one that would give dosing close to weighing the shot manually. Any input from people that have a machine with a high pressure meter and have weighed the shot would be greatly appreciated.

Posted February 22, 2012 link

If a machine's pump is steady enough that it puts a constant amount of water out, then shouldn't timed doses be the same as metered doses? I would think (but I'm new) that the metered amount of water could still be choked by a puck that is too tamped or too finely ground. Maybe timed doses aren't that inferior?
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germantownrob
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germantownrob
Joined: 2 Dec 2007
Posts: 2,156
Location: Philadelphia
Expertise: I love coffee

Espresso: Duetto 3, A Dead Oscar
Grinder: Vario-W, Preciso w/Esatto,...
Drip: Brazen
Roaster: Diedrich IR-1, HT B
Posted Thu Feb 23, 2012, 11:59am
Subject: Re: Question about volumetric dosing?
 

Gig103 Said:

If a machine's pump is steady enough that it puts a constant amount of water out, then shouldn't timed doses be the same as metered doses? I would think (but I'm new) that the metered amount of water could still be choked by a puck that is too tamped or too finely ground. Maybe timed doses aren't that inferior?

Posted February 23, 2012 link

A timed dose will be effected by the puck ( grind size and dose size), if you get 2oz of water in 24sec and adjust grind  finer and or dose a little more the timer will still just give you 24 sec of water but since the flow through the puck is restricted you would not get 2oz of water. If the opv is set to 9.5 bar but the flow through the puck is restricted then it will send water that should be going to pf back to the reservoir ( or drip tray in my case) the timer will still give you 24sec of flow but you will not get 2oz through the puck, this is the issues will a low pressure flow meter as well.
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MARIOBARBA
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MARIOBARBA
Joined: 26 Sep 2011
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Location: MONTREAL CANADA
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Espresso: Ascaso DUO Prof TRONIC
Grinder: Baratza Vario
Posted Thu Feb 23, 2012, 12:21pm
Subject: Re: Question about volumetric dosing?
 

germantownrob Said:

If the opv is set to 9.5 bar but the flow through the puck is restricted then it will send water that should be going to pf back to the reservoir ( or drip tray in my case) the timer will still give you 24sec of flow but you will not get 2oz through the puck, this is the issues will a low pressure flow meter as well.

Posted February 23, 2012 link

That is exactly what happens in my case, the shot usually comes up short since I have a penchant for ristrettos.  Loosening the grind helps with consistency but hurts the flavour.  I usually go a click or two coarser on the Vario if I am doing a milk drink and want to take advantage of the automation to focus on the steam.  The coming up short is not an issue when doing straight espresso because I enjoy watching the flow almost as much as drinking the shot and so go the semi-auto route in those cases.

I was wondering if anyone with an automatic machine that stopped short on them ever restarted the shot and what the results would be like?
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Gig103
Senior Member


Joined: 12 Feb 2012
Posts: 244
Location: Arizona
Expertise: I like coffee

Espresso: Crossland CC1
Grinder: Baratza Vario
Drip: French press!
Posted Thu Feb 23, 2012, 9:54pm
Subject: Re: Question about volumetric dosing?
 

germantownrob Said:

A timed dose will be effected by the puck ( grind size and dose size), if you get 2oz of water in 24sec and adjust grind  finer and or dose a little more the timer will still just give you 24 sec of water but since the flow through the puck is restricted you would not get 2oz of water. If the opv is set to 9.5 bar but the flow through the puck is restricted then it will send water that should be going to pf back to the reservoir ( or drip tray in my case) the timer will still give you 24sec of flow but you will not get 2oz through the puck, this is the issues will a low pressure flow meter as well.

Posted February 23, 2012 link

AHA! I didn't realize that there was an OPV in place. I see then how a volumetric reading *after* that valve would be the best way, then.
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