Posted Sat May 27, 2006, 7:51pm Subject: Accurate group head temperature readings? What are you using?
Would love to hear of what some of you guys are using to register accurate head temp readings... Are you getting good results? I am looking to put a better unit than what I am using together and would appreciate any tips in this regard. I've heard that Jaycar have a great readout unit. Carlos.
Posted Sun May 28, 2006, 12:49am Subject: Re: Accurate group head temperature readings? What are you using?
hey i was just about to post up a thread regarding my analyisis of temperature readings. I use my multimeter with a K-Type thermocouple with long wire so i can snake it up into the basket. The main issue here is finding a position that is accurate and consistant. I find that the thermocouple is very sensitive and if you position it differently you will get mixed results.
After reading alot about temp reading i decided to give it a go. Snaked it up the portafilter, drilled hole in the basket then measured it, but i new it just was not accurate enough.
So i used the blind filter and snaked the thermometer into the basket and got better results and i was able to simulate brew pressures at the same time because water can escape gently due to the seal being slightly open because of the wire leading into the basket. But the results were still hit and miss and we not giving me the same temps as i would get when doing the extraction due to the different postions the thermometer is in the basket. I find that there are to many variables unless you can attach a PID or find a secure consistant mounting point. But seemings you are building your machine you will probably be able to figure out something.
Luca Moderator Joined: 27 Jan 2004 Posts: 2,639 Location: Melbourne, Australia
Espresso: H: Maver W: FB-80 Grinder: H: Super Jolly W: Brasilia... Vac Pot: Hario TCA-2 Roaster: Sample Roaster at Work
Posted Sun May 28, 2006, 3:49am Subject: Re: Accurate group head temperature readings? What are you using?
Is this for the Veneziano, Carlos? If so, I reckon that this might be the way to go ... this is similar, but I guess that you probably want to use a multimeter, right?
Here's what Dan had to say about the adaptor in the first link:
The utility of Eric's adapter is plainly evident to me: By tuning the flush amount based on the adapter's TC reading, reproducible temperatures are easily obtained within ~1F.
Cheers,
Luca
PS. Jaw dropped yet? I thought it was pretty cool ...
Sparkman Senior Member Joined: 14 Jun 2005 Posts: 358 Location: Brisbane, Australia Expertise: I love coffee
Espresso: La Pavoni Bar T2/Faema... Grinder: Cimbali Cadet/Gaggia MDF
Posted Sun May 28, 2006, 5:44am Subject: Re: Accurate group head temperature readings? What are you using?
I used to snake a K-type thermocouple over the lip of the basket and onto the top of the coffee puck. It works well, but you do destroy the thermocouples after maybe 20-30 uses. It is also heavy on the coffee for what is ostensibly a diagnostic pourpose.
I use a Digitech QM1538 multimeter from Jaycar, but source the thermocouples from Dick Smith (as they have the teflon coated ones). The multimeter has an RS232 output and I use that to thermolog my machines. I strongly recommend thermologging over spot measurements. You get a much greater understanding of what the temperature is doing. It is also advisable to calibrate each thermocouple individually. I do this using a digital food thermometer that is rated to +/- 1C accuracy. In addition both boiling and freezing points were used to test the calibration thermometer. This gives the K-type TC better than 1 C accuracy.
Ultimately the procedure outlined above is not convenient for taking many successive readings. That's where the Scace device comes in. I have just made my own version of this device with an adjustable needlevalve that can be used to set the required flow rate. I've tested the needle valve and it works as designed. I've now inserted the K-type TC and am waiting for the silicone to cure. I'll give it at least 5 more days until I trial it properly. It, like the scace device, should be the ultimate in temperature measuring diagnostic tool... I hope... This device is installed in a standard double filter basket. It requires a naked PF to be used.
If I was in Hobart, I'd pop down and test your machines for you. If you're really interested, it may be possible for me to make up a second device and send it down to you (time permitting). Best wait for the trial though.
Otherwise I'd go with what Luca suggested for the E61 grouphead.
Regards,
Mark.
PS I should point out that most thermocouple reading instruments aren't very accurate. The QM1538 multimeter has an accuracy of +/- 3 C. In the region of espresso brewing it's accuracy is near its worst, being systematically 3 C higher than the true temperature. Thermocouples are nonlinear in their response, there are not many instruments that fully take this into account. Be sure to look at the rated accuracy of any instrument you use, especially if you want to use it to determine the optimal brew temperature for a particular blend for customer use. You can't have people setting their Synesso's to the wrong temp ;-)
Posted Sun May 28, 2006, 3:29pm Subject: Re: Accurate group head temperature readings? What are you using?
Thanks guys , LUCA IAM LOCO ( ? ) , and BRENTLING, these are very cool tips and suggestions, and I am going to read through this carefully this arvo and put something together. Thankyou for your efforts, very helpful!
Posted Sun May 28, 2006, 3:41pm Subject: Re: Accurate group head temperature readings? What are you using?
Hey Sparkman! Nice to hear from you. Fantastic resolutions there. The adjustable needle valve is the go for sure. How are you measuring the flow rate? Yep, if the new prototype works, I'd be keen on purchasing your new model, fresh off the factory floor ( kitchen table ? ) . Thanks again. Carlos.
Posted Tue May 30, 2006, 5:18pm Subject: Re: Accurate group head temperature readings? What are you using?
I'm thinking of getting one of these things (Eric's thermocouple adapter) and would like to know what exact model of thermocouple and guage to get. I would prefer the most reasonable ones that work well and hold up. I'm not an engineer so don't use too many abbreviations. Thanks. Michael
Posted Tue May 30, 2006, 6:19pm Subject: Re: Accurate group head temperature readings? What are you using?
mgwolf Said:
I'm thinking of getting one of these things (Eric's thermocouple adapter) and would like to know what exact model of thermocouple and guage to get. I would prefer the most reasonable ones that work well and hold up. I'm not an engineer so don't use too many abbreviations. Thanks. Michael
or call them...tell them you want a "HTTC36-K-116G-2.25"
HTTC= Hollow Tube ThermoCouple 36=36" inches of wire k=type k miniature plug (yours may be a diferent type of reader and require a different letter here, omega sales girl will know) 116G=1/16" diameter 2.25=2.25" long.
its a "custom" part and will take 10 business days. it wont be in the inventory. i think it was about $26US
this info is in eric documents that he refers to in the thread i listed above. ( he suggests using a 2" long HTTC but i got a 2.25")
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