La Marzocco Linea Mini - accuracy of PID dial's settings

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lcats
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#1: Post by lcats »

My new Linea Mini arrived a couple of days ago, as did an HG-One which I decided on to replace my Mazzer Mini grinder. It is quite a treat to have such equipment, and I think I have got myself in the ballpark with the settings and like my results (they could still be improved), but have a question about the LM's PID.

On my machine, the analogue dial is labeled "199.6°", then "203°", then "206.6°" (and other settings above and below these) and between these settings there are eight or nine clickstops each. The machine arrived with this set at 203°. Of course I can experiment on various settings (already I am at 3 clicks above 203°), but I have no idea whether the labeled temps are anywhere near accurate and if so, at what point during the pull they might have been calibrated for. I have asked locally for a Scace, but am not sure there is one as available here as previously, when I adjusted the PID on my previous machine. I certainly do not mean to obsess about this, like some do with a digital readout, but I would like to know where I am at.

I'd just like to know if anyone here can comment on the accuracy of the these PID dial's settings, or whether they are just a general reference.

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weebit_nutty
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#2: Post by weebit_nutty »

From HB's tests. I'm extremely surprised someone bought this machine without reading the reviews written for it, primarily the rather comprehensive review on this very site. Here's the post Dan Kehn's wrote on his Scace tests.

Perhaps you are of the TLDR type.. Well, the short of it is that the temp is very stable. As to the dial setting-- It's only a dial meant for adjustment not a readout. The readout should be on your tongue, as this machine was designed primarily as a basic, but extremley reliable home machine, for the skilled barista that dial their shots by taste, not numbers.


Anyway
You're not always right, but when you're right, you're right, right?

JonF
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#3: Post by JonF »

I was kind of hoping to see a reply to the original question too.

Did Dan happen to mention what the dial was set at? That would directly address the question. Sorry if I missed it. Thanks!

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keno
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#4: Post by keno »

lcats wrote:On my machine, the analogue dial is labeled "199.6°", then "203°", then "206.6°" (and other settings above and below these) and between these settings there are eight or nine clickstops each. The machine arrived with this set at 203°. Of course I can experiment on various settings (already I am at 3 clicks above 203°), but I have no idea whether the labeled temps are anywhere near accurate and if so, at what point during the pull they might have been calibrated for.

I'd just like to know if anyone here can comment on the accuracy of the these PID dial's settings, or whether they are just a general reference.
Sounds like LM tweaked the numbers on the dial. Mine has only whole numbers, no decimals.



I think you are correct that the only way to truly verify the accuracy would be to use a Scace at the group head. But that's no different than a digital PID, since it's not reading the temp at the puck. I'm sure LM calibrates them at the factory and my experience using it suggests that it's probably reasonably accurate as light roasts are tasting best around 203 and darker roasts closer to 198. But as someone else said, best thing is just to adjust by taste.

JonF
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#5: Post by JonF »

Thanks Keno! I have been looking all over for a photo of the actual dial!

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keno
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#6: Post by keno »

keno wrote:Sounds like LM tweaked the numbers on the dial. Mine has only whole numbers, no decimals.
Looking at my own photo I now see that what I said above is incorrect. :oops: The dial says 199.4 when I zoom in on it. I couldn't read the ".4" part with the naked eye because it's so small!

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Bob_McBob
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#7: Post by Bob_McBob »

It's 199.4°F because it's converted from 93°C. Silly they didn't just calibrate the scale in Fahrenheit to begin with, but they probably perform the same factory calibration and just stick a different dial on it for the North American market. Not that the numbers are particularly meaningful if there is an offset or ambient temperature affects things significantly.
Chris

lcats (original poster)
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#8: Post by lcats (original poster) »

I did try to read all that was available on H-B and elsewhere on the Linea Mini, prior to pulling to trigger and ordering one. What Dan Kehn wrote on his Scace tests convinced me of the temperature stability inherent in this unit. I crave repeatability, which I had not been able to get previously with my much lesser equipment.

What I am writing about here is simpler, perhaps just a matter of convenience. If the analogue dial of the Linea Mini's PID had shown only A . . . B . . .C . . and so on, not degrees on the thermometer, I could live with that, and use taste to calibrate it for a particular roast. Still, I would then associate, let's say "two clicks beyond B" with a particular temperature, let's say 202°, if that worked out to be the correct setting for a blend that I had from previous experience decided that 202° on some other machine's read-out was where I wanted to be.

All that I am wondering here, is what the numbers on the Linea Mini's PID dial really mean. Do they correlate with what's in my head, or are they completely arbitrary? From reading here, perhaps we already know that these settings are repeatable also, but I am not completely certain of that either.

And thanks for the deciphering of the 199.4° and so on being just a direct conversion from Celsius. I should have figured that out.

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jeffb
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#9: Post by jeffb »

I am very interested in purchasing a Linea Mini and I emailed the OP asking about his impressions. (Thank You for the reply) I also am interested in the dial setting vs actual temp.
Just checked the LaMarzocco website and it lists part assembly for Linea Mini and other machines. The PID is apparently built on the Main Circuit board and the Temperature Sensor is a type N Thermocouple (Standard: +/- 2.2C or +/- .75% accuracy).

I am an Engineer that has worked with and specified PID's for the Industrial world and am very familiar with the digital LED controllers often used to Mod or as part of PID'd Espresso machines.

I like the Linea Mini due to it's simplicity, even though it has no digital readout, it is PID controlled and should be very accurate.

If a PID control has a digital readout, it usually has the ability to "offset" to the "accurate" temperature. due to the "accuracy" of the sensor (normally RTD or Thermocouple) the readout needs adjusted. Undoubtedly the Linea Mini's are calibrated at the factory, so will be interested if the 203 dial setting truly equals 203?

It is assumed that when you see "203"F on a digital readout, that it is accurate and IS 203, however, due to the inherent accuracy of the sensor and control and the "time" also involved in the sensing...the readout could be "off".....the good thing about the Mini is that with no readout, you can assume that the true temperature is as it is set, still considering the variables mentioned. Any thoughts that this machine is less accurate and less repeatable than the GS3 with Digital readout is false, in my opinion.

The GS3 ability to change preinfusion is obviously different, however I would assume only "taste" could discern a difference!

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weebit_nutty
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#10: Post by weebit_nutty »

lcats wrote:All that I am wondering here, is what the numbers on the Linea Mini's PID dial really mean. Do they correlate with what's in my head, or are they completely arbitrary? From reading here, perhaps we already know that these settings are repeatable also, but I am not completely certain of that either.
The numbers are only an estimation of the actual temp. But because there is no dial indicator, it's a guess exactly where it resides along the dial.

But as to the repeatability, it's extremely stable. I've tested mine multiple times when I first got it. first with thermapen at the group, then my home-made scace.
You're not always right, but when you're right, you're right, right?

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