| |
Main
Date: 28 Oct 2006 19:50:32
From: Phil P
Subject: continuation of pressure vs temp in a PIDed HX
|
(Apologies for starting a new thread, but I didn't want to revive the
commercial posting)
On 27 2006 14:08:07 -0700, "Phil P" <charneyb...@yahoo.com > wrote:
>>I->Ian wrote:
>>> On 27 2006 10:09:52 -0700, "Phil P" <charneyb...@yahoo.com> wrote:
>>> >daveb wrote:
>>> >[snip more spam]
>>> >> 2) Full power 'HX' with more accurate control over pressures, and NO
>>> >> clicking, clacking etc.
>>> >Why would you care about boiler pressure now that you're controlling
>>> >temperature directly?
>>> Steaming?
>>Again it's linked more with the water temp and volume; you can't hope
>>to accurately control pressure during steaming and it's no longer
>>relevant when the boiler is idling. Just seems like an irrelevence iro
>>the commercial advertiser's product.
>Don't know about other HX pid10t's but better foam is produced here
>when starting with ~1.2bar/~250F than with ~0.6bar/~234F, normal shot
>pulling SV temp.
>When making frufru, crank SV temp to ~250F and steaming is much
>easier, always starting with the same pressure...
>The above is what I understood "2) Full power 'HX' with more accurate
>control over pressures" to mean.
Ian, I can see that longtime HX machine users are accustomed to
thinking in terms of pressure, and to using the dial to monitor the
boiler state. My point was that pressure is just used as an analog for
temperature in p-stat machines. Once you are able to control and
display the temperature directly, it's no longer technically necessary
to talk in terms of a parameter one step removed from the one you're
really interested in. Whereas Dave's marketing spiel seemed to be
suggesting that controlling boiler pressure was still the ultimate
objective.
With your example, you're using pressure as your primary metric for
recording the place you choose to start steaming from, but really it's
the corresponding water temperature that matters. The instant that
steam valve is cracked open, the pressure reading becomes irrelevant to
the process and it's just the temperature of the boiler water that's
dictating the steaming performance. The point I take from you though
is that some people might prefer to continue using pressure as their
primary reference even though the direct temperature value is now
available via the PID.
(btw, what's frufru?) :)
|
|
| |
Date: 29 Oct 2006 04:18:46
From: daveb
Subject: a PIDed HX -- i.e. the Quickmill Vetrano, or ISomac Tea or Millenium or . .
|
P:
The entire purpose ot the 'pid' on HX is to deliver flexibility,
control, reliability and precision.
1) The USER controls pressures.
2) The heat can be lowered so that the unit acts like a single boiler
machine and makes ESPRESSO without purging water and guessing.
3) The heat can be RAISED to deliver whatever pressure is desired on
the manometer. A preset can be stored in the controller for optimal
ESPRESSO and another for optimal HX. [and in steam, the primary metric
IS pressure]
4) There are NO moving parts: no contacts, no wear, NO clicking /
clacking, no sticking, no drift and NO replacement, repair or service
needed.
The USER determines what the machine does -- by controlling the heat
energy delivered to the system.
dave b
139.5
Phil P wrote:
> (Apologies for starting a new thread, but I didn't want to revive the
> commercial posting)
>
>
> On 27 2006 14:08:07 -0700, "Phil P" <charneyb...@yahoo.com> wrote:
>
> >>I->Ian wrote:
> >>> On 27 2006 10:09:52 -0700, "Phil P" <charneyb...@yahoo.com> wrote:
>
>
> >>> >daveb wrote:
>
>
> >>> >[snip more spam]
>
>
> >>> >> 2) Full power 'HX' with more accurate control over pressures, and NO
> >>> >> clicking, clacking etc.
>
>
> >>> >Why would you care about boiler pressure now that you're controlling
> >>> >temperature directly?
>
>
> >>> Steaming?
>
>
> >>Again it's linked more with the water temp and volume; you can't hope
> >>to accurately control pressure during steaming and it's no longer
> >>relevant when the boiler is idling. Just seems like an irrelevence iro
> >>the commercial advertiser's product.
>
>
> >Don't know about other HX pid10t's but better foam is produced here
> >when starting with ~1.2bar/~250F than with ~0.6bar/~234F, normal shot
> >pulling SV temp.
>
> >When making frufru, crank SV temp to ~250F and steaming is much
> >easier, always starting with the same pressure...
>
> >The above is what I understood "2) Full power 'HX' with more accurate
> >control over pressures" to mean.
>
>
> Ian, I can see that longtime HX machine users are accustomed to
> thinking in terms of pressure, and to using the dial to monitor the
> boiler state. My point was that pressure is just used as an analog for
> temperature in p-stat machines. Once you are able to control and
> display the temperature directly, it's no longer technically necessary
> to talk in terms of a parameter one step removed from the one you're
> really interested in. Whereas Dave's marketing spiel seemed to be
> suggesting that controlling boiler pressure was still the ultimate
> objective.
>
> With your example, you're using pressure as your primary metric for
> recording the place you choose to start steaming from, but really it's
> the corresponding water temperature that matters. The instant that
> steam valve is cracked open, the pressure reading becomes irrelevant to
> the process and it's just the temperature of the boiler water that's
> dictating the steaming performance. The point I take from you though
> is that some people might prefer to continue using pressure as their
> primary reference even though the direct temperature value is now
> available via the PID.
>
> (btw, what's frufru?) :)
|
| |
Date: 29 Oct 2006 15:32:00
From: Phil P
Subject: Re: continuation of pressure vs temp in a PIDed HX
|
I- >Ian wrote:
> On 28 2006 19:50:32 -0700, "Phil P" <charneybarn@yahoo.com> wrote:
>
> >(btw, what's frufru?) :)
>
> my term for corrupted espresso...
>
> and a corruption of frou-frou :
> - elaborate decoration, as frills, ribbons, or ruffles, esp. on
> women's clothing.
Excellent! i might use that . . .
|
| |
Date: 29 Oct 2006 22:24:56
From: I->Ian
Subject: Re: continuation of pressure vs temp in a PIDed HX
|
On 28 2006 19:50:32 -0700, "Phil P" <charneybarn@yahoo.com > wrote:
>(btw, what's frufru?) :)
my term for corrupted espresso...
and a corruption of frou-frou :
- elaborate decoration, as frills, ribbons, or ruffles, esp. on
women's clothing.
|
| |
Date: 30 Oct 2006 09:57:34
From: daveb
Subject: a PIDed HX
|
In addition to the improved reliability you cite, the lack of acoustic
noise (as in the Sirai) the lack of drift, the controller allows the
unit to be optimized for production of coffee, rather than steam.
In my contact with customers who have // or are looking at HX they
USUALLY want 1 or 2 GOOD cups of espresso in the morning,-- with a
lower starting 'pid' temp setting -- with the option of cranking up
the heat to make milk drinks that require steam and a series of shots
-- as when one may be entertaining guests. -- [in the Vetrano, moving
from optimal espresso temps to HX operation takes only 80 seconds.]
I, too, could frankly care less about steam temp. but the 'pid'
premits easy control of that pressure, with the TC probe immersed IN
the boiler water.
and it'll read out in C or F.
Dave
140.5
www.hitechespresso.com
Jack Denver wrote:
> I don't exactly agree with what you are saying. No one (at least not me) is
> interested in steam boiler temperature per se, which is what your PID
> readout gives you in a HX setup. The steam boiler temp IS one step removed
> from the number you are really interested in (the brew temp), so it is no
> more useful a figure than boiler pressure (they are both equally good or bad
> at predicting brew temp). I have my steam boiler set at around 122C, which
> is really a worthless bit of information, except that I have determined thru
> trial and error that this gives me the circa 95C BREW temperature that I'm
> interested in. If the readout was of brew temp, that would be a directly
> meaningful #, but it ain't in a HX PID setup.
>
> In terms of milk steaming, pressure is more useful to know than temp - it's
> temp that is one step removed. Of course it's not that hard to look it up
> and know that 122C is roughly 1.1 bar gauge pressure, 123 is 1.2, 120 is
> 1.0, etc. I can also see pressure drop while steaming - the boiler might
> drop to 116 or 117 (.8 bar) and then recover once the steam valve is closed.
> The units (bar, psi, degrees, whatever) are really not that important - what
> you want to know is the direction and magnitude of the deviation from your
> "normal" setpoint whether you call normal 122C or 15PSI or whatever.
>
> Of course you are right that temp and pressure are proxies for each other in
> a sealed boiler. With a proper translation table or algorithm, the voltage
> that the thermcouple is generating could just as well be expressed as bars
> of pressure as it could degrees of temperature but AFAIK there's no PID that
> can do this at present.
>
> The bottom line though is that a PID setup for a HX is a useful improvement
> IMHO. In my case what I liked best about it was the improvement in
> reliability. I was getting less than 1 year out of each mini-pstat in my
> Oscar and would often wake to the sound of my safety valve blowing, but
> since the PID conversion my sleep has been undisturbed. If your machine has
> a pressure gauge to begin with (mine didn't so the readout was an added
> bonus in that it gave me more info than I had before) you can of course keep
> using it. You can even put the PID in a place that is not visible if you
> don't care for the temp readout and want to maintain your "stock"
> appearance.
>
>
>
>
>
>
>
>
> "Phil P" <charneybarn@yahoo.com> wrote in message
> news:1162090232.632011.168900@i42g2000cwa.googlegroups.com...
> > (Apologies for starting a new thread, but I didn't want to revive the
> > commercial posting)
> >
> >
> >>>> >> 2) Full power 'HX' with more accurate control over pressures, and NO
> >>>> >> clicking, clacking etc.
> >
> >
> >>>> >Why would you care about boiler pressure now that you're controlling
> >>>> >temperature directly?
> >
> >
> >>>> Steaming?
> >
> >
> >>>Again it's linked more with the water temp and volume; you can't hope
> >>>to accurately control pressure during steaming and it's no longer
> >>>relevant when the boiler is idling. Just seems like an irrelevence iro
> >>>the commercial advertiser's product.
> >
> >
> >>Don't know about other HX pid10t's but better foam is produced here
> >>when starting with ~1.2bar/~250F than with ~0.6bar/~234F, normal shot
> >>pulling SV temp.
> >
> >>When making frufru, crank SV temp to ~250F and steaming is much
> >>easier, always starting with the same pressure...
> >
> >>The above is what I understood "2) Full power 'HX' with more accurate
> >>control over pressures" to mean.
> >
> >
> > Ian, I can see that longtime HX machine users are accustomed to
> > thinking in terms of pressure, and to using the dial to monitor the
> > boiler state. My point was that pressure is just used as an analog for
> > temperature in p-stat machines. Once you are able to control and
> > display the temperature directly, it's no longer technically necessary
> > to talk in terms of a parameter one step removed from the one you're
> > really interested in. Whereas Dave's marketing spiel seemed to be
> > suggesting that controlling boiler pressure was still the ultimate
> > objective.
> >
> > With your example, you're using pressure as your primary metric for
> > recording the place you choose to start steaming from, but really it's
> > the corresponding water temperature that matters. The instant that
> > steam valve is cracked open, the pressure reading becomes irrelevant to
> > the process and it's just the temperature of the boiler water that's
> > dictating the steaming performance. The point I take from you though
> > is that some people might prefer to continue using pressure as their
> > primary reference even though the direct temperature value is now
> > available via the PID.
> >
> > (btw, what's frufru?) :)
> >
|
| |
Date: 30 Oct 2006 10:21:43
From: Jack Denver
Subject: Re: continuation of pressure vs temp in a PIDed HX
|
I don't exactly agree with what you are saying. No one (at least not me) is
interested in steam boiler temperature per se, which is what your PID
readout gives you in a HX setup. The steam boiler temp IS one step removed
from the number you are really interested in (the brew temp), so it is no
more useful a figure than boiler pressure (they are both equally good or bad
at predicting brew temp). I have my steam boiler set at around 122C, which
is really a worthless bit of information, except that I have determined thru
trial and error that this gives me the circa 95C BREW temperature that I'm
interested in. If the readout was of brew temp, that would be a directly
meaningful #, but it ain't in a HX PID setup.
In terms of milk steaming, pressure is more useful to know than temp - it's
temp that is one step removed. Of course it's not that hard to look it up
and know that 122C is roughly 1.1 bar gauge pressure, 123 is 1.2, 120 is
1.0, etc. I can also see pressure drop while steaming - the boiler might
drop to 116 or 117 (.8 bar) and then recover once the steam valve is closed.
The units (bar, psi, degrees, whatever) are really not that important - what
you want to know is the direction and magnitude of the deviation from your
"normal" setpoint whether you call normal 122C or 15PSI or whatever.
Of course you are right that temp and pressure are proxies for each other in
a sealed boiler. With a proper translation table or algorithm, the voltage
that the thermcouple is generating could just as well be expressed as bars
of pressure as it could degrees of temperature but AFAIK there's no PID that
can do this at present.
The bottom line though is that a PID setup for a HX is a useful improvement
IMHO. In my case what I liked best about it was the improvement in
reliability. I was getting less than 1 year out of each mini-pstat in my
Oscar and would often wake to the sound of my safety valve blowing, but
since the PID conversion my sleep has been undisturbed. If your machine has
a pressure gauge to begin with (mine didn't so the readout was an added
bonus in that it gave me more info than I had before) you can of course keep
using it. You can even put the PID in a place that is not visible if you
don't care for the temp readout and want to maintain your "stock"
appearance.
"Phil P" <charneybarn@yahoo.com > wrote in message
news:1162090232.632011.168900@i42g2000cwa.googlegroups.com...
> (Apologies for starting a new thread, but I didn't want to revive the
> commercial posting)
>
>
>>>> >> 2) Full power 'HX' with more accurate control over pressures, and NO
>>>> >> clicking, clacking etc.
>
>
>>>> >Why would you care about boiler pressure now that you're controlling
>>>> >temperature directly?
>
>
>>>> Steaming?
>
>
>>>Again it's linked more with the water temp and volume; you can't hope
>>>to accurately control pressure during steaming and it's no longer
>>>relevant when the boiler is idling. Just seems like an irrelevence iro
>>>the commercial advertiser's product.
>
>
>>Don't know about other HX pid10t's but better foam is produced here
>>when starting with ~1.2bar/~250F than with ~0.6bar/~234F, normal shot
>>pulling SV temp.
>
>>When making frufru, crank SV temp to ~250F and steaming is much
>>easier, always starting with the same pressure...
>
>>The above is what I understood "2) Full power 'HX' with more accurate
>>control over pressures" to mean.
>
>
> Ian, I can see that longtime HX machine users are accustomed to
> thinking in terms of pressure, and to using the dial to monitor the
> boiler state. My point was that pressure is just used as an analog for
> temperature in p-stat machines. Once you are able to control and
> display the temperature directly, it's no longer technically necessary
> to talk in terms of a parameter one step removed from the one you're
> really interested in. Whereas Dave's marketing spiel seemed to be
> suggesting that controlling boiler pressure was still the ultimate
> objective.
>
> With your example, you're using pressure as your primary metric for
> recording the place you choose to start steaming from, but really it's
> the corresponding water temperature that matters. The instant that
> steam valve is cracked open, the pressure reading becomes irrelevant to
> the process and it's just the temperature of the boiler water that's
> dictating the steaming performance. The point I take from you though
> is that some people might prefer to continue using pressure as their
> primary reference even though the direct temperature value is now
> available via the PID.
>
> (btw, what's frufru?) :)
>
|
| |
Date: 30 Oct 2006 16:24:49
From: Phil P
Subject: Re: continuation of pressure vs temp in a PIDed HX
|
Jack Denver wrote:
> I don't exactly agree with what you are saying. No one (at least not me) is
> interested in steam boiler temperature per se, which is what your PID
> readout gives you in a HX setup. The steam boiler temp IS one step removed
> from the number you are really interested in (the brew temp), so it is no
> more useful a figure than boiler pressure (they are both equally good or bad
> at predicting brew temp). I have my steam boiler set at around 122C, which
> is really a worthless bit of information, except that I have determined thru
> trial and error that this gives me the circa 95C BREW temperature that I'm
> interested in. If the readout was of brew temp, that would be a directly
> meaningful #, but it ain't in a HX PID setup.
Agreed, in a sealed boiler there's little to choose between the two.
But since it is the hot water that gives rise to the steam pressure,
and the steam pressure probably takes longer to equilize than water
temp, and since the HX and element are immersed in the water, I would
still give water temp the edge as reference of choice.
>
> In terms of milk steaming, pressure is more useful to know than temp - it's
> temp that is one step removed. Of course it's not that hard to look it up
> and know that 122C is roughly 1.1 bar gauge pressure, 123 is 1.2, 120 is
> 1.0, etc. I can also see pressure drop while steaming - the boiler might
> drop to 116 or 117 (.8 bar) and then recover once the steam valve is closed.
> The units (bar, psi, degrees, whatever) are really not that important - what
> you want to know is the direction and magnitude of the deviation from your
> "normal" setpoint whether you call normal 122C or 15PSI or whatever.
That's a good point about the rate/trend information that can be gained
from the boiler pressure gauge during steaming indicating whether
demand is outstripping the rate of evaporation, etc., and I concede
that the pressure gauge is useful to have for that reason alone. But .
. .
The pressure and water temp are giving different information during
steaming, as opposed to when the boiler is sealed, and I think it is
the water temp that best represents the reserve of steaming power left
in the boiler. Since this is what determines the rate of steam
production, I still think it is the more valuable parameter overall.
It doesn't fluctuate in the way pressure does during steaming and so is
indicating that reserve capacity while the pressure gauge is instead
giving the different short-term trend info.
>
> Of course you are right that temp and pressure are proxies for each other in
> a sealed boiler. With a proper translation table or algorithm, the voltage
> that the thermcouple is generating could just as well be expressed as bars
> of pressure as it could degrees of temperature but AFAIK there's no PID that
> can do this at present.
>
> The bottom line though is that a PID setup for a HX is a useful improvement
> IMHO. In my case what I liked best about it was the improvement in
> reliability. I was getting less than 1 year out of each mini-pstat in my
> Oscar and would often wake to the sound of my safety valve blowing, but
> since the PID conversion my sleep has been undisturbed. If your machine has
> a pressure gauge to begin with (mine didn't so the readout was an added
> bonus in that it gave me more info than I had before) you can of course keep
> using it. You can even put the PID in a place that is not visible if you
> don't care for the temp readout and want to maintain your "stock"
> appearance.
>
Those reasons certainly make a persuasive argument for the pid on an
HX, particularly the freedom from p-stats.
>
> "Phil P" <charneybarn@yahoo.com> wrote in message
> news:1162090232.632011.168900@i42g2000cwa.googlegroups.com...
> > (Apologies for starting a new thread, but I didn't want to revive the
> > commercial posting)
> >
> >
> >>>> >> 2) Full power 'HX' with more accurate control over pressures, and NO
> >>>> >> clicking, clacking etc.
> >
> >
> >>>> >Why would you care about boiler pressure now that you're controlling
> >>>> >temperature directly?
> >
> >
> >>>> Steaming?
> >
> >
> >>>Again it's linked more with the water temp and volume; you can't hope
> >>>to accurately control pressure during steaming and it's no longer
> >>>relevant when the boiler is idling. Just seems like an irrelevence iro
> >>>the commercial advertiser's product.
> >
> >
> >>Don't know about other HX pid10t's but better foam is produced here
> >>when starting with ~1.2bar/~250F than with ~0.6bar/~234F, normal shot
> >>pulling SV temp.
> >
> >>When making frufru, crank SV temp to ~250F and steaming is much
> >>easier, always starting with the same pressure...
> >
> >>The above is what I understood "2) Full power 'HX' with more accurate
> >>control over pressures" to mean.
> >
> >
> > Ian, I can see that longtime HX machine users are accustomed to
> > thinking in terms of pressure, and to using the dial to monitor the
> > boiler state. My point was that pressure is just used as an analog for
> > temperature in p-stat machines. Once you are able to control and
> > display the temperature directly, it's no longer technically necessary
> > to talk in terms of a parameter one step removed from the one you're
> > really interested in. Whereas Dave's marketing spiel seemed to be
> > suggesting that controlling boiler pressure was still the ultimate
> > objective.
> >
> > With your example, you're using pressure as your primary metric for
> > recording the place you choose to start steaming from, but really it's
> > the corresponding water temperature that matters. The instant that
> > steam valve is cracked open, the pressure reading becomes irrelevant to
> > the process and it's just the temperature of the boiler water that's
> > dictating the steaming performance. The point I take from you though
> > is that some people might prefer to continue using pressure as their
> > primary reference even though the direct temperature value is now
> > available via the PID.
> >
> > (btw, what's frufru?) :)
> >
|
| |
Date: 31 Oct 2006 07:05:26
From: gscace
Subject: Re: continuation of pressure vs temp in a PIDed HX
|
Hi:
I'm a little late on jumping, but water vapor / steam is my area of
professional expertise, so a coupla comments are imbedded.
Phil P wrote:
> Jack Denver wrote:
> > I don't exactly agree with what you are saying. No one (at least not me) is
> > interested in steam boiler temperature per se, which is what your PID
> > readout gives you in a HX setup. The steam boiler temp IS one step removed
> > from the number you are really interested in (the brew temp), so it is no
> > more useful a figure than boiler pressure (they are both equally good or bad
> > at predicting brew temp). I have my steam boiler set at around 122C, which
> > is really a worthless bit of information, except that I have determined thru
> > trial and error that this gives me the circa 95C BREW temperature that I'm
> > interested in. If the readout was of brew temp, that would be a directly
> > meaningful #, but it ain't in a HX PID setup.
>
> Agreed, in a sealed boiler there's little to choose between the two.
> But since it is the hot water that gives rise to the steam pressure,
> and the steam pressure probably takes longer to equilize than water
> temp, and since the HX and element are immersed in the water, I would
> still give water temp the edge as reference of choice.
The two are coupled very closely. Upsetting the thermodynamic
applecart causes very rapid changes. For example, immediate violent
boiling and temperature reduction occurs if the steam valve is opened.l
The response time of the process is sufficiently fast that temperature
is certainly a fine parameter to use as a feedback signal.
>
> >
> > In terms of milk steaming, pressure is more useful to know than temp - it's
> > temp that is one step removed. Of course it's not that hard to look it up
> > and know that 122C is roughly 1.1 bar gauge pressure, 123 is 1.2, 120 is
> > 1.0, etc. I can also see pressure drop while steaming - the boiler might
> > drop to 116 or 117 (.8 bar) and then recover once the steam valve is closed.
> > The units (bar, psi, degrees, whatever) are really not that important - what
> > you want to know is the direction and magnitude of the deviation from your
> > "normal" setpoint whether you call normal 122C or 15PSI or whatever.
>
> That's a good point about the rate/trend information that can be gained
> from the boiler pressure gauge during steaming indicating whether
> demand is outstripping the rate of evaporation, etc., and I concede
> that the pressure gauge is useful to have for that reason alone. But .
> . .
>
> The pressure and water temp are giving different information during
> steaming, as opposed to when the boiler is sealed, and I think it is
> the water temp that best represents the reserve of steaming power left
> in the boiler. Since this is what determines the rate of steam
> production, I still think it is the more valuable parameter overall.
> It doesn't fluctuate in the way pressure does during steaming and so is
> indicating that reserve capacity while the pressure gauge is instead
> giving the different short-term trend info.
>
> >
> > Of course you are right that temp and pressure are proxies for each other in
> > a sealed boiler. With a proper translation table or algorithm, the voltage
> > that the thermcouple is generating could just as well be expressed as bars
> > of pressure as it could degrees of temperature but AFAIK there's no PID that
> > can do this at present.
this is an important point. We aren't actually measuring temperature.
We're measuring voltage potential of dissimilar wires that is produced
by having two dissimilar wire connections at different temperatures.
Also, PID refers to a type of control algorithm. Most controllers
don't care what device produces the feedback signal, as long as the
device produces the proper voltage or current, and as long as the
feedback device is well coupled to the process. You could just as
easily use a pressure transducer for control, but the cheapest
transducers are still around a hunnert bux, and thermocouples are dirt
cheap. Nice thermocouples installed inside a stainless steel sheath,
with nicely finished leads etc are around 25 bux.
> >
> > The bottom line though is that a PID setup for a HX is a useful improvement
> > IMHO. In my case what I liked best about it was the improvement in
> > reliability. I was getting less than 1 year out of each mini-pstat in my
> > Oscar and would often wake to the sound of my safety valve blowing, but
> > since the PID conversion my sleep has been undisturbed. If your machine has
> > a pressure gauge to begin with (mine didn't so the readout was an added
> > bonus in that it gave me more info than I had before) you can of course keep
> > using it. You can even put the PID in a place that is not visible if you
> > don't care for the temp readout and want to maintain your "stock"
> > appearance.
> >
>
> Those reasons certainly make a persuasive argument for the pid on an
> HX, particularly the freedom from p-stats.
Ease of setpoint adjustment, control stability, reliability all point
to PID control as a good solution for espresso machines. On the bad
side, pressurestats react faster and turn the heater on full-blast.
It's a niggling issue compared to the plusses.
-Greg
>
>
>
> >
> > "Phil P" <charneybarn@yahoo.com> wrote in message
> > news:1162090232.632011.168900@i42g2000cwa.googlegroups.com...
> > > (Apologies for starting a new thread, but I didn't want to revive the
> > > commercial posting)
> > >
> > >
> > >>>> >> 2) Full power 'HX' with more accurate control over pressures, and NO
> > >>>> >> clicking, clacking etc.
> > >
> > >
> > >>>> >Why would you care about boiler pressure now that you're controlling
> > >>>> >temperature directly?
> > >
> > >
> > >>>> Steaming?
> > >
> > >
> > >>>Again it's linked more with the water temp and volume; you can't hope
> > >>>to accurately control pressure during steaming and it's no longer
> > >>>relevant when the boiler is idling. Just seems like an irrelevence iro
> > >>>the commercial advertiser's product.
> > >
> > >
> > >>Don't know about other HX pid10t's but better foam is produced here
> > >>when starting with ~1.2bar/~250F than with ~0.6bar/~234F, normal shot
> > >>pulling SV temp.
> > >
> > >>When making frufru, crank SV temp to ~250F and steaming is much
> > >>easier, always starting with the same pressure...
> > >
> > >>The above is what I understood "2) Full power 'HX' with more accurate
> > >>control over pressures" to mean.
> > >
> > >
> > > Ian, I can see that longtime HX machine users are accustomed to
> > > thinking in terms of pressure, and to using the dial to monitor the
> > > boiler state. My point was that pressure is just used as an analog for
> > > temperature in p-stat machines. Once you are able to control and
> > > display the temperature directly, it's no longer technically necessary
> > > to talk in terms of a parameter one step removed from the one you're
> > > really interested in. Whereas Dave's marketing spiel seemed to be
> > > suggesting that controlling boiler pressure was still the ultimate
> > > objective.
> > >
> > > With your example, you're using pressure as your primary metric for
> > > recording the place you choose to start steaming from, but really it's
> > > the corresponding water temperature that matters. The instant that
> > > steam valve is cracked open, the pressure reading becomes irrelevant to
> > > the process and it's just the temperature of the boiler water that's
> > > dictating the steaming performance. The point I take from you though
> > > is that some people might prefer to continue using pressure as their
> > > primary reference even though the direct temperature value is now
> > > available via the PID.
> > >
> > > (btw, what's frufru?) :)
> > >
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Date: 31 Oct 2006 14:08:23
From: Jack Denver
Subject: Re: continuation of pressure vs temp in a PIDed HX
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I wonder why this is other than lack of volume and resulting economies of
scale? Digital tire gauges are under $10 nowadays and this includes not
only the transducer but a battery and a display. They are meant for cool dry
air and not hot wet steam but still...
"gscace" <gregory.scace@nist.gov > wrote in message
news:1162307126.715957.110860@h48g2000cwc.googlegroups.com...
You could just as
> easily use a pressure transducer for control, but the cheapest
> transducers are still around a hunnert bux, and thermocouples are dirt
> cheap.
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