jpender Senior Member Joined: 11 Jul 2011 Posts: 402 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Thu Jan 31, 2013, 11:56am Subject: Re: Strange problem with weighing water for V60
Nice to see you got to the bottom of it.
There must be a thermal carafe that would suit your needs. Even a glass one would be better than metal. In the meantime why not just use a hot pad, a piece of ensolite, or a copy of Everything But Espresso?
Unfortunately the spec sheets for inexpensive scales tend to lack details. Temperature sensitivity is usually given in ppm/°C and for a cheap scale would be in the tens of ppm, not enough to cause you a problem. But that's within operating temperature limits. Setting a metal container of really hot water on the metal weighing pan almost certainly pushes it outside of these (unstated) limits. I tried this last night with my cheapo scale (American Weigh SM-501). I poured boiling water into an aluminum bottle, sealed it and placed it directly on the metal pan. After about 5 minutes of this mistreatment the scale drifted 0.5%, not enough to have been noticible during a pourover. Either your scale is more sensitive to mistreatment or your carafe got it a lot hotter than my aluminum bottle got my scale.
edit: From the CJ-4000 manual:
"Avoid lengthy exposure to extreme heat or cold, your scale works best when operated at normal room temperature."
"Do not operate near an in-use cell phone, cordless phone, radio, computer or other electronic device. These devices emit RF and can cause unstable scale readings."
Posted Thu Jan 31, 2013, 12:23pm Subject: Re: Strange problem with weighing water for V60
The temperature sensitivity quoted will be measured with the scale at the same temperature throughout - it'll be an environmental temperature. With a hot coffee carafe on top, you're heating one part more than the others, and the sensitivity could be much higher.
A cork mat or similar would probably be good enough insulation for the duration of a V60 pour.
jpender Senior Member Joined: 11 Jul 2011 Posts: 402 Location: California Expertise: I like coffee
Grinder: Kyocera CM-50 Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Thu Jan 31, 2013, 4:52pm Subject: Re: Strange problem with weighing water for V60
dyqik Said:
The temperature sensitivity quoted will be measured with the scale at the same temperature throughout - it'll be an environmental temperature. With a hot coffee carafe on top, you're heating one part more than the others, and the sensitivity could be much higher.
That may be true as well. The point I was making was that the sensitivity drift (had it been specified for the Jennings) would only be valid over a limited temperature range.
This could lead to great thread about which books work best. For instance, I've gotten poor results insulating with books published by Random House -- my readings were all over the place.
Posted Fri Feb 1, 2013, 7:24am Subject: Re: Strange problem with weighing water for V60
I do the same thing with a preheated mug right on the metal of my CJ-4000 and have never had the spurious readings that you are reporting. I am glad insulation solved your problem. Perhaps they reengineered more recent models (mine is about 10 months old). I will look out for the same. Thank you for your post and I am glad someone knew the solution. B
yakster Senior Member Joined: 25 Feb 2009 Posts: 1,006 Location: San Jose, CA Expertise: I live coffee
Espresso: Gaggia Factory / La Peppina... Grinder: Vario / Kyocera Vac Pot: Yama 8 + Pyrex Lox-in Rod Drip: Brazen / Kalita / Chemex /... Roaster: Behmor
Posted Fri Feb 1, 2013, 11:35pm Subject: Re: Strange problem with weighing water for V60
I'd heard of this in various places but it really came to light for me when Able Brewing ran into it with the Elite Scale 1000. They ended up pulling the product back and liquidating their inventory from what I can glean from Twitter.
I picked up four cork coasters for a buck or two to use on the scale at home and work.
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