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  • Dimal
    replied
    Re: pour temperature question

    Originally posted by slowdown link=1197367483/15#18 date=1197633052
    it tells me that the idea of taking the temperature over the puck with the doodad is just laughable... its like got an 80% confidence interval (see I can get technical too!) of about 7.8375342 degrees C.
    This is a huge generalisation SD and really taken out of context. You can carry out your own experiments if you like, very simple..... Do a series of tests with a K Type t/c and the Data Logging DMM that Andy has available through BeanBay or the same unit bought from Jaycar. Im not sure where you live but if at Sea Level then we all know that pure water will boil at 100°C. If you live at an Elevation either above or below SL then you apply the correction factor that applies to your Elevation.

    Next, run a series of measurements and record the results.... First measure the temperature of vigorously boiling water, then immerse the t/c junction into a large glass containing crushed water-ice, then back to the boiling water.
    Compare the recorded results and note the variation. Head over to your Elevation Tables and note the corrective factor you need to use for your current Elevation then see how far the results differ from the empirical data. I doubt you will find a significant variation and I feel pretty sure that repeatability will also be very tight. For our purposes, this is a very reliable and accurate method to use with variability held to quite tight tolerances which Im sure you will confirm should you decide to undertake the simple experiment outlined above.

    Sure, if youre going to use the same t/c and DMM for measurements that range from one extreme of the K-Type t/cs capability to the other then there are calibration steps that need to be taken to ensure the results are meaningful. This is absolutely unnecessary within the range of 0-100°C though. Hope this helps a bit mate ,

    Cheers,
    Mal.

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  • slowdown
    replied
    Re: pour temperature question

    Hmmm... its so hard to keep up with this website. Now Im reading this link

    http://coffeesnobs.com.au/YaBB.pl?num=1197616758

    just after the above post (synchronicity!) and it tells me that the idea of taking the  temperature over the puck with the doodad is just laughable... its like got an 80% confidence interval (see I can get technical too!) of about 7.8375342 degrees C.

    LOL eh. Skip that idea. So much for roast temperatures too via the same route methinks.

    So back to my point, maybe just simmering is a good reference point? I have googled a bit but I havent been able to find out exactly what temperature water simmers - but someone must know. And yes, lets talk sea level, and ambient temperature of say 15 degrees - a lovely morning in Perth, as usual.

    Anyone?

    Leave a comment:


  • slowdown
    replied
    Re: pour temperature question

    Im reading this with interest. All that control stuff is a bit over my head. However, I have a a related question: can one deduce 92 degrees as being the point where the water exiting from the shower screen is just (not) steaming?

    I will eventually get onto the Jaycars website and get a doodad to read the temperature over the grounds -utilising the beady thingy over the lip of the portafilter, plugged into the temperature thingy, which may or may not attach to my computer if Im prepared to spend $50 for a serial to USB etc etc

    But for now, is this just steaming (or just simmering, as we cooks might call it) a reasonable rule of thumb for a good brew temperature????

    Leave a comment:


  • roknee
    replied
    Re: pour temperature question

    Originally posted by Mal link=1197367483/15#15 date=1197464942

    Hope this is useful... [smiley=laugh.gif]

    Mal.
    hey mal
    thanks so much
    will let you know how i go after i have a good squizz...

    aaron

    Leave a comment:


  • Dimal
    replied
    Re: pour temperature question

    Hi again roknee,

    Not exactly mate, theres a whole lot more to it than that. My understanding is that the Minore has excellent temperature stability as an espresso machine in toto, you cant just isolate the control methodology out of the mix when it is the whole machines performance you need to look at.

    If youre not familiar with the principles of PID control and how this is integrated into a specific machines design, then perhaps I could recommend some reading material for you, namely..... Embedded Systems

    Hope this is useful... [smiley=laugh.gif]

    Mal.

    Leave a comment:


  • roknee
    replied
    Re: pour temperature question

    Originally posted by Mal link=1197367483/0#13 date=1197442925
    Originally posted by roknee link=1197367483/0#12 date=1197437988
    as well as an add-on PID?

    aaron
    Not sure if youre referring to my post above roknee but in case you are..... As you may know, PID represents and acronym for a controller with Proportional, Integral and Derivative control elements.

    In the case of the Minore, it uses a simple Proportional only controller and thus allows for the existence of a constant error between the SetPoint and the Process Variable. By adjusting the gain of the controller (probably preset in the case of the Minore) it is possible to achieve quite acceptable levels of control, as owners of the Minore can testify to. So long as the error between the SP and the PV is known, it is a simple matter of accruing the error quantity into the SP and the PV will be maintained at this setting.

    Hope this helps you out....

    Mal.
    hey Mal
    thanks, I was referring to your prev post!

    so i take it that the expo has a simplified version of a pid? and therefore somewhat less stable temps??

    am i on the right track here?  :-?

    ta

    aaron

    Leave a comment:


  • Dimal
    replied
    Re: pour temperature question

    Originally posted by roknee link=1197367483/0#12 date=1197437988
    as well as an add-on PID?

    aaron
    Not sure if youre referring to my post above roknee but in case you are..... As you may know, PID represents and acronym for a controller with Proportional, Integral and Derivative control elements.

    In the case of the Minore, it uses a simple Proportional only controller and thus allows for the existence of a constant error between the SetPoint and the Process Variable. By adjusting the gain of the controller (probably preset in the case of the Minore) it is possible to achieve quite acceptable levels of control, as owners of the Minore can testify to. So long as the error between the SP and the PV is known, it is a simple matter of accruing the error quantity into the SP and the PV will be maintained at this setting.

    Hope this helps you out....

    Mal.

    Leave a comment:


  • roknee
    replied
    Re: pour temperature question

    as well as an add-on PID?

    aaron

    Leave a comment:


  • Dimal
    replied
    Re: pour temperature question

    Originally posted by JavaB link=1197367483/0#10 date=1197434288
    I dont know the expo minoreII, but if the digital display is actually a PID then it should make quite some difference. There are however some other forms of digital display which arent really a PID (but a cut down version of one) and they wouldnt be quite as good.
    Gday JB,

    From what Ive been able to find out mate, the control on a Minore II, etc is a simple Proportional Controller and so long as you know the degree of error (for setpoint purposes), it can manage the boiler temp quite well ,

    Mal.

    Leave a comment:


  • JavaB
    replied
    Re: pour temperature question

    aaron,

    In theory .... it might.

    I dont know the expo minoreII, but if the digital display is actually a PID then it should make quite some difference. There are however some other forms of digital display which arent really a PID (but a cut down version of one) and they wouldnt be quite as good.

    A machine can have a digital display, and the temperature still droop during extraction whilst one without a display could be very temperature stable - but not easily adjustable. Generally speaking..... it costs money to design a quality machine.... and that cost is passed on to the purchaser....

    With coffee machines - the more you pay, the better the machine will be designed and the closer it will maintain the correct temperature.... that is a sweeping generalisation.... but pretty accurate. Also most machines can be "tweaked" to perform even better. If you buy your machine from a reputable dealer (like a site sponsor).... this will be done for you pre sale.

    It is generally not a good idea to try and "tweak" a machine yourself unless you really, really know what you are doing and how the changes will affect the tuning of the machine (PID adjustment of course excepted)

    Leave a comment:


  • roknee
    replied
    Re: pour temperature question

    hi jb
    thanks so much for going into the detail you did. v. helpful. and i now have a better understanding of why temps drop...

    so, if i go back to basic lingo for a minute (easier on my noggin)...i can recall that some machines like the expo minoreII have a digital control panel on them where you can adjust brew temp. would this facilitate better extraction as compared to a machine like the expo office, as temp could be adjusted according to the blend, bean etc?

    Leave a comment:


  • JavaB
    replied
    Re: pour temperature question

    aaron,

    There is no simple answer to what is a good design and what isnt.

    The main reason for temperature drop during a shot is the cold water being forced in so that the heated water is displaced into the coffee grinds. This cold water (depending on design of the boiler) can reduce the extraction temperature....

    So a large boiler will reduce the effect
    Correct "injection" of cold water will reduce the effect
    A heater circuit which responds quickly will reduce the effect

    Commercial machines and prosumer class machines use pressurestats to control boiler pressure (and therefore temperature) and because they switch over a small range.... they maintain the temperature very well.

    A PID fitted to smaller single boiler machines (and each boiler of multiple boiler machines - like a Synesso) do this very well also.

    Multiple boilers arent necessarily better than single boilers - they are if correctly designed (again like the Synesso).... A large single boiler will be more stable than a small brew boiler and a larger steam boiler.

    By the way the OPV changes brew pressure.... (Over Pressure Valve) adjusting the thermostat or PID on single boiler or the brew boiler (on multi boiler machines) adjusts the brew temperature..... as does adjusting the pressurestat on a commercial or prosumer........

    In the case of a prosumer and especially a commercial - adjusting the pressurestat wont effect brew temperature that much.... there is a lot more in the design of these machines to make them stable.... the actual HX temperature being just one. Cooling flushes also pay an important role in setting brew temperature on these machines.

    The only way to easily and repeatably adjust brew temperature is to have a machine where the boiler, or at least the brew boiler of multiple boiler machines, is under PID control.

    Leave a comment:


  • roknee
    replied
    Re: pour temperature question

    thanks jb
    ive also wondered about the value of buying a dual boiler (ala expo minore) or hx with the easy ability to tweak opvs (which i understand changes pour temp) vs hxs that dont (or at least not easily..
    what are your thoughts?

    aaron

    Leave a comment:


  • JavaB
    replied
    Re: pour temperature question

    roknee,

    That depends on the machine and the way it has been designed.....

    The larger commercials (like mine) dont drop at all, whereas poorly designed small single boiler machines do drop quite a bit as do thermoblock machines if the water flow is too high (rate of normal extraction is exceeded). And yet other boiler machines will drop just a little. A poorly designed machine can actually increase the temp during the pour.

    It is more a factor of the design of the machine and generally speaking the end user cant do anything about it (other than buy a quality machine and use it correctly).

    Leave a comment:


  • roknee
    replied
    Re: pour temperature question

    so from what im hearing the main problem with temp during the pour, is that the temp drops off somewhat, right?

    Leave a comment:

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