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Thread: Sunbeam EM5800 temperature analysis

  1. #1
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    Sunbeam EM5800 temperature analysis

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    [shock! horror! newbie warning! low-end machine discussion ahead... etc :o]

    I borrowed a thermocouple meter from work last night and did some probing of my little machine.

    Sunbeam EM5800: thermoblock, electronic temperature control system. Plastic (GFRP?) group head.
    Meter: Dick Smith twin thermocouple meter. resolution 1C, I calibrated it against boiling water and ice water, accuracy ~1C.

    Test 1) free-flow temperatures from group head. No PF of filter, shower screen removed, temp probe jammed up the water outlet port. pre-programmed double shot button (dispenses about 100ml when theres no restriction). Probably not the "proper" way, but its a harsher test than with a slower flow rate.

    1st shot (as soon as the "ready" lights came on, ~2 minutes after power-on): 68! :o

    did a few more shots and left it to warm up for a longer time. Between shots the probe would stabilise around 94-97, but as soon as the water started flowing it would dip, sometimes peak a little, but then fall off towards the end of the shot.

    Typically, 96 prior to the shot, then the shot temp would run from 88-77.


    I did a couple more tests with the probe in the filter and the PF (brass) screwed in (used a pressurised filter to slow the flow rate) - still with no coffee in it though. Temps were more stable, but I think thats because the junction was sitting in some water in the bottom of the filter. Still, it was too cold at ~88C.
    I only did a couple of those runs though, before water started leaking down the wire insulation and wetting the meter!


    But it looks like Ive got some tinkering to do....

  2. #2
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    Re: Sunbeam EM5800 temperature analysis

    Teeheehee ... Ive got some good news for you ...

    (a) First up, the matchup between most multimeter/probe setups and the true value is usually not good. John Bicht is an engineer with years of experience, who recently built the M3 espresso machine in America. He posted to Home-Barista.com to explain the error inherent in the equipment: http://www.home-barista.com/forums/viewtopic.php?p=4463

    So I wouldnt take the numbers at face value ...

    Also note that Johns discussion doesnt even take into account technique, which can account for radical differences in results.

    (b) The method that you used to measure the temperature is inappropriate for a thermoblock machine. Greg (kaanage) explained this in a post on coffeegeek: http://www.coffeegeek.com/forums/worldregional/australasia/237669#237669

    Ive tried to hyperlink directly to the post above, but Im sure that Greg wont mind if I quote him here for everyones convenience:

    OK, I have to disagree with Alans analysis of the EM6900s temp as he did it using a method that suits boiler and HX machines but is totally misleading for most thermoblock machines. The approach of punching out a double shots worth of water without any restriction is fine for a boiler or HX machine as the boiler (steam boiler for a HX) is a thermal reservoir that should supply water at the right temp for a volume far greater than that of a double espresso shot. The boiler acts as a very large thermal buffer between the heating elements and the water that enters and leaves the boiler or HX tube.

    In a thermoblock machine, the thermoblock itself is the only thermal reservoir and has far, far less heat capacity than even a Gaggia sized boiler so it depends on the heating elements operating on the water passing through the passages to ensure that the correct temperature is reached by the time the water exits the thermoblock. Now assuming that the water in the tank is 25 deg C and the required temp at exit is 93 deg C (a 68 deg C temp increase), every ml of water will need 68 Calories of heat energy added => 285 joules. Now the unrestricted flow though the EM6900 will be in the order of 60ml in 10 seconds so for the correct water temp to be reached, the heating elements would be required to add about 17 kilojoules of heat which corresponds to 1700W of heating power if there are no losses (ha!). Now the EM6900 has a 1000W heating element for each of its thermoblocks so it cannot keep up with the energy demand for unrestricted flow so the water flowing into the cup drops off in temp asymtopically towards the steady state unrestricted flow temp - about 64 deg C

    BUT if the flow is restricted to proper extraction times (60ml in 25 sec) the average heating power required drops to about 680W so the thermoblock has more than enough heating power to reach the required output temp and will cycle the heating elements on and off to keep the temperature in the proper range.

    As long as the temperature control circuits in the EM6900 are up to scratch and calibrated properly, it should have no trouble delivering the required shot temperature for a properly ground, dosed and tamped shot (it should work fine down to about a 19 second double shot - allowing for a bit of heat loss). In fact if it was sufficiently sophisticated, shot temperature control could be better than any traditional machine.

    Greg
    Personally, I think that temperature measurement in espresso really only has two applications:

    -Ensuring consistent temperatures in shots (most relevant to learning how to flush HX machines)

    -Comparing temperatures and setting machines up to the right temperature but only when using the same measuring equipment and technique

    It is true that on our Synesso at work we often do things like going to 199.5F as a starting point for a darker roast or something like that, but this is an illustration where the equipment doing the measurement is kept constant, so the errors in measurement between two temperatures can be expected to cancel each other out. If I were to take the same coffee requiring 199.5F and use it on a domestic HX machine, for example, I wouldnt bother with the whole thermometry thing, Id just tweak the pstat by taste.

    Hope that gives you some hope and wasnt too technical,

    Luca

  3. #3
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    Re: Sunbeam EM5800 temperature analysis

    nah, thats not too complex. Id argue one point about the power consumption though.

    As I said, I expected that the free-flow situation would be a harsher test than with a flow resistance in place. Thats why I also did the last test with the pressurised filter, which slows the flow to a similar level to proper extraction.

    However, if you are willing to tolerate a certain amount of temperature drop across the shot (and lets not open that can of worms here), then you dont need a thermoblock with the same power rating as (flow*temp diff*Cp), because the block itself is dumping heat into the water as the block cools, essentially acting as a "power" source.

    That aside, Ive had the feeling that my shots have been a bit sour, and a brew temp of 88 would seem to back that up.

    Over the weekend if I have some time I plan to repeat the tests using coffee in the filter, and the probe on top of that.

    After that I want to try tweaking the temperature setting, which can apparently be done on this machine.

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    Re: Sunbeam EM5800 temperature analysis


    With a thermoblock, or a heat exchanger machine for that matter, you definitely need to run the machine at proper brewing flow rates to get a reasonable idea. You also get way more insight into the behaviour of the machine if you can log the temperature profile. As Luca suggested, getting an absolute accuracy can be quite tricky, so its best to let your tastebuds do the talking.

    I spoke with Damian Court from Sunbeam the other day. He definitely said the temperature on the EM5800 was adjustable using a small screw on the circuit board. He also said the temperature on the new EM6900 was adjustable. I dont think many people know that and he didnt tell me how to do it.

    Good luck with it.

    Cheers,

    Mark.

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    Re: Sunbeam EM5800 temperature analysis

    cheers for the confirmation sparky. Like I said, the pressurised filter in place slows the flow to "normal" rates, and the temperature under that scenario was quite stable (though cold).

    Im fairly confident in the thermometers accuracy, as I said I checked it against two reference points...

    just got my CS bean delivery this arvo, so might waste a few over the weekend in testing with coffee in place, and temp tweaking...


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    Re: Sunbeam EM5800 temperature analysis

    OK, back with more data...

    I pulled some shots tonight with the TC stuffed in on top of the puck. Firstly I recalibrated the gauge at boiling point to read ~99-100 though.

    1st shot (after ~15-20 minutes warmup and some warming flushes): 86 falling to 84 after ~70ml.

    2nd shot (again with a flush before): 90, dipped to 88 then finished at 90.

    3rd shot (as before): 89 falling to 87.

    In general, it seems that the temperature stability is pretty good (only a 2 degree drop from start to finish), but a fraction too cold.

    Taste: hmm, Im not sure Im equipped to comment. Im not an espresso drinker (yet ;)), so it just tastes "frickin intense"(TM). Plus I think I overextracted the shots a bit.

    I think I really need to spend a session with a good barista tasting espressos and learning what the nuances of flavour are, and the effects of variables.

    Next step is to tweak the temp up a bit and see (taste) what the effects are. (actually I lie, first is roast more beans so I have something to test and drink)

    the fun continues...

  7. #7
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    Re: Sunbeam EM5800 temperature analysis

    Quote Originally Posted by luca link=1151024858/0#1 date=1151027398
    Teeheehee ... Ive got some good news for you ...

    (a) First up, the matchup between most multimeter/probe setups and the true value is usually not good. John Bicht is an engineer with years of experience, who recently built the M3 espresso machine in America. He posted to Home-Barista.com to explain the error inherent in the equipment: http://www.home-barista.com/forums/viewtopic.php?p=4463

    So I wouldnt take the numbers at face value ...

    Luca
    Just had a look at the above post in Home Barista. In general what John says is ok, except for one small item.... he makes reference to a simple equation for converting Celsius to Fahrenheit, namely degrees C x 1.8 to convert to Fahrenheit. Unfortunately, this conversion formula is incorrect. The correct formula for this conversion is.... (degC/5 X 9) + 32 = Fahrenheit. If you do a couple of calculations using both formulae you will notice that this is where a lot of the so-called error creeps in.

    Mal.

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    Re: Sunbeam EM5800 temperature analysis

    So he forgot the temp offset. Not good if youre trying to convert. Otherwise, the article really talks about accuracy in temp readings. Ive found this is really difficult. For example, I have calibrated my probes against a known reference using over 60 data points. It should be accurate to within +/- first crack, but I find the corrected readings seem to be systematically low when in use. In fact the uncorrected readings seem to be closer to what Id expect. Im going to recalibrate the probe, but this does illustrate that absolute accuracy can require some very careful procedures to ensure that what youre reading is close to the truth, and more to the point is repeatable from measurement to measurement and machine to machine. That is one of the main motivators for the Scace thermofilter and one of the reasons I built a similar device.

    So I find thermometry really good for relative measurements. Its excellent for checking a flush routine on a HX machine or checking how long it takes for a PIDed boiler to restabilize before pulling another shot. It will also show you how stable the temp is during a shot. An example of that is on my Bezzera, I pulled the gicleur out of my machine as my machines was taking a long time to come up to pressure. When I did some thermologging on it I found the temps were all over the place. Im not sure I understand it, but the gicleur is going back in and Im replacing the pump and Ill revisit those measurements again after all that.

    Matt, great news on the Sunbeam. A second crack drop is in Silvia territory. That means youve really got a tightband thermostat in that machine. The main thermoblock problem was the use of cheap bimetallic thermostats with an 8-10C dead band. These are completely inappropriate for thermoblocks.

    I expect that once you adjust the temp up a bit, youll probably be making really nice shots with that rig. Keep us updated.

    Cheers,

    Mark.

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    Re: Sunbeam EM5800 temperature analysis

    I said in another thread that Id love to see the actual heater on/off cycle - need to add a light to it...

    As per the first post though, if you just measure free-flowing water, it drops by 11 degrees over about 100 ml!

    temp tweak, and if I find a good regulator Ill add that, and it could be a fun little unit. Then I just need my roasting skills to improve, and the eleventy bizillion other factors...

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    Re: Sunbeam EM5800 temperature analysis

    I played with a friends new em5800 the other day - they have a new steam arm that looks a bit fatter, and thats about the only difference I could see.

    But what I could feel was a different story - that cup warming surface gets frigging hot! Much hotter than my ol SB.

    Made a decent shot of East Timor Leste Maubese, with the pressurised basket and all.

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    Re: Sunbeam EM5800 temperature analysis

    Quote Originally Posted by Mal link=1151024858/0#6 date=1151078980
    Just had a look at the above post in Home Barista. In general what John says is ok, except for one small item.... he makes reference to a simple equation for converting Celsius to Fahrenheit, namely degrees C x 1.8 to convert to Fahrenheit. Unfortunately, this conversion formula is incorrect. The correct formula for this conversion is.... (degC/5 X 9) + 32 = Fahrenheit. If you do a couple of calculations using both formulae you will notice that this is where a lot of the so-called error creeps in.

    Mal.
    So he forgot the temp offset. Not good if youre trying to convert.
    The way I understand it, the post talks about magnitude of error, not actual values ... doesnt that mean that the offset is irrelevant? For example, isnt John saying that if you use a typical setup, like this one:

    DVM typical with E type standard = within 6.96 degrees F
    <snip>
    with J or K type standard = within 7.96 degrees F
    You have a 7.96 F margin of error, so if your reading is 199.5F, the actual value (absolute value? am I getting my terms mixed up? am I making sense?) is 199.5F +/- more or less 8F, so the temp is actually somewhere between 191.5F and 207.5F. If the DVM is displaying in C, wont it just read 93.0C, and the actual value will be 93.0C +/- about 4.4C, so between 89.6C and 97.4C ... which is the equivalent in C, by my calculations.

    In other words, isnt it true that your formula, Mal, is relevant to the 199.5F/93C bit, but Johns is relevant to the +/- 7.96F/4.4C bit? If so, I think that the above is a pretty powerful illustration of the point; if your thermocouple reads what might be your target temperature of 93C, you could actually be brewing above 97C, which, I can assure you will taste very different.

    Just some food for thought ... we were playing around with matching some of Marks blend from St Ali with different jams today. We thought that at 203.0F (according to our Synesso) it was really citrusy and matched apricot jam and orange marmalade quite well. At 200.0F it was a lot more chocolatey and matched fig jam and hazelnut spread a lot better. So there you go, Matt, you might be able to adjust temperature by jam!

    Cheers,

    Luca

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    Re: Sunbeam EM5800 temperature analysis

    Quote Originally Posted by Sparky link=1151024858/0#7 date=1151115838
    So he forgot the temp offset. Not good if youre trying to convert. Otherwise, the article really talks about accuracy in temp readings.

    Cheers,

    Mark.
    One would have thought that if one is going to pen thoughts of this nature then it would be prudent, even responsible, to ensure that everything one has written stands up to all over scrutiny, especially something as basic as forgetting the offset in temp conversion calcs. I appreciate the work you do Sparky, as Im sure do a lot of CS members, and the diligence you apply to all aspects of what you are prepared to publish. Stable temperature is very important, as we all know, but it is not the be-all end-all to achieving great coffee on a consistent basis.... even you have attested to the fact that one of the best coffees you ever tasted came from an unmodified Gaggia Classic :o, so all is not absolutely clear.

    Cheers,
    Mal.

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    Re: Sunbeam EM5800 temperature analysis

    ...erm I think you mean a slightly modified Gaggia Classic, with PID control, pressure mod and additional metal on the boiler.

    The magic that makes the money shot or god shot or whatever you want to call it depends on many factors. Im not sure anyone really knows whats required. With taste being subjective, its a bit of a soft science anyway. One thing that is important is repeatability. If you can repeat the conditions, then you should be able to repeat the shot. Thats where these high end machines come into their own.

    Mal, we all make mistakes. Nevertheless, John Bicht has made one very impressive machine, grinder and tamper... He understands about repeatability. He obviously understands about thermal design, thats why its worth listening to what he says, errors aside.

    Cheers,

    Mark.

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    Re: Sunbeam EM5800 temperature analysis

    Quote Originally Posted by mattyj link=1151024858/0#9 date=1151152199
    I played with a friends new em5800 the other day - they have a new steam arm that looks a bit fatter, and thats about the only difference I could see.

    But what I could feel was a different story - that cup warming surface gets frigging hot! Much hotter than my ol SB.

    Made a decent shot of East Timor Leste Maubese, with the pressurised basket and all.
    I had one of the old ones. Replaced it under warrnty with one of the new ones. Steam arm was about the only observable difference. The ditched the "foam enhancer" too, probably trying to target a more educated market...

    sorry, no time for machine tweaking this weekend. did some work on the popper, thats another story. Maybe more next week.

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    Re: Sunbeam EM5800 temperature analysis

    Quote Originally Posted by Mal link=1151024858/0#11 date=1151160682
    Quote Originally Posted by Sparky link=1151024858/0#7 date=1151115838
    So he forgot the temp offset. Not good if youre trying to convert. Otherwise, the article really talks about accuracy in temp readings.

    Cheers,

    Mark.
    One would have thought that if one is going to pen thoughts of this nature then it would be prudent, even responsible, to ensure that everything one has written stands up to all over scrutiny, especially something as basic as forgetting the offset in temp conversion calcs. I appreciate the work you do Sparky, as Im sure do a lot of CS members, and the diligence you apply to all aspects of what you are prepared to publish. Stable temperature is very important, as we all know, but it is not the be-all end-all to achieving great coffee on a consistent basis.... even you have attested to the fact that one of the best coffees you ever tasted came from an unmodified Gaggia Classic :o, so all is not absolutely clear.

    Cheers,
    Mal.
    Mal, I think that you must have been typing this post as I was typing mine above! Anyhoo, to reiterate my question from above with rather less verbiage, isnt the offset irrelevant to magnitude of error? Isnt first crack (the magnitude) 1.8F?

    Cheers,

    Luca

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    Re: Sunbeam EM5800 temperature analysis

    Behmor Brazen - $249 - Free Freight
    Quote Originally Posted by Matt King link=1151024858/0#2 date=1151034533
    nah, thats not too complex. Id argue one point about the power consumption though.

    As I said, I expected that the free-flow situation would be a harsher test than with a flow resistance in place. Thats why I also did the last test with the pressurised filter, which slows the flow to a similar level to proper extraction.

    However, if you are willing to tolerate a certain amount of temperature drop across the shot (and lets not open that can of worms here), then you dont need a thermoblock with the same power rating as (flow*temp diff*Cp), because the block itself is dumping heat into the water as the block cools, essentially acting as a "power" source.
    2 things here.
    1. The empty PF does not restrict the initial flow properly as the air pocket is compressible (even assuming that the water immediately covers the little hole so the PF is psuedo sealed) so the early flow rate is still too fast.

    2. I did say in the post Luca quoted that the thermoblock thermal storage was a lot lower than that of a boiler. It may not be nothing but it is small enough for misleading temp drops in unrestricted flow tests. In a restricted flow test, inadequate heating power will give a lesser drop but the SB thermoblocks are more than powerful enough for realistic flow rates.

    It seems that the thermostat used for the single thermoblock SBs are set rather on the low side by default. Nice thast they are adjustable, though.

    Greg



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