Howdy, Been reading about folks adding a digital temperature probe to their roasters and suddenly remembered that I happened to have one of these. It was a freebie that the vendor threw in when I purchased my DVM. But, I am concerned whether it can be used with my air popper. Here's the specs: Type K thermocouple sensor Fast responding handles temp range of -40F to 482F Designed for gas and surface measurements The tip of the cable has a beaded sensor for air measurements What do y'all think? Can I poke this through the cover on my popper and seal the opening with some high temp silicon glue? Does this have enough range for coffee roasting? Thanks for your sage advice! Darren Do you Yahoo!? Y! Web Hosting - Let the expert host your web sitehttp://lists.sweetmarias.com/mailman/listinfo/homeroast">http://webhosting.yahoo.com/homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Darren wrote: <Snip> Sure. Note that if you permanently attach it to your popper, you won't be able to throw it in the dishwasher anymore... -- Rick homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
<Snip> It is very unlikely that you wold ever exceed 482 in your popper. I'd go for it. homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Peculiar . . . I find a reply to this question, but can't find the original post. <Snip> If you're talking about the $19.95 device mentioned previously . . . it's hard to figure how they arrived at the "482F" upper limit. The bead probe that comes with it certainly works at temperatures well above that (as does the box itself). Most probably the "limit" comes from a little piece of shrink wrap at the end of the probe lead, there to prevent fraying of the fiber insulation, or the insulation itself (which should be fiberglass, but isn't . . . I just flame tested it and it burns). I'd at least cut off the shrink wrap . . . But, more generally, be careful with bead or wire thermocouples. Thermocouple wire is quite brittle, and mechanical failure of the junction is almost a certainty if it's long exposed to banging around in a mosh pit of roasting beans. I posted a "hint" a few days ago about how to make a simple (and cheap) thermowell (1/8" thinwall tubing . . . SS is about $3.00 a foot at the local hardware, high temp heat sink compound from Radio Shack or anywhere (you only put it in the last 1/4" of the tube, just enough to connect the bead to the wall, so you don't need much), crimpers or pliers you've already got, threaded fittings or swagelocs you don't need) . . . you probably saw it already. You'll get more consistent and more reliable readings with a well, and, if you put a dab of sealant in the "other end" of the tube, a much higher temperature rating for the insulation (no air, can't burn ). The "art" of temperature measurement lies in knowing what you want to measure, and getting a probe in place to measure it. Rick Farris posted an interesting note last week comparing thermocouple with an "analog" (mechanical dial) thermometer. The thermocouple disclosed that the dial thermometer was *not* reading bean temperature, but an undefined combination of bean temperature and roast chamber temperature (and thus always too high). While the dial got closer to correct at the end of the roast (where the bean/chamber differential is smallest), and clearly has at least some utility for determining roast endpoint, it would be useless for "profile roasting" since at no point during the roast did it accurately measure bean temperature. That same dial thermometer, were it mounted so more of the tip/shaft was "in the beans" and the rest of the shaft was either at ambient or insulated from the roast air, would probably work just fine. I can (obviously ) go on about this stuff far beyond most peoples interest (or patience) . . . if you've got questions probably better to ask direct (off the list) so as not to bore everybody . . . Deward homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Rick, I'm not planning on putting this one through the diskwasher. The probe is very small and attached to a long braided nylon cord that the wires run through. I don't think it will hold up to washing and the box states specifically that it is not designed for use in liquids. I know some build up will occur over use from coffee smoke and oils, but I don't think that I should have to remove it to clean it occasionally. Is the temp range on this probe OK? Thanks, Darren Darren wrote: <Snip> Rick replied: <Snip> <Snip> Do you Yahoo!? Y! Web Hosting - Let the expert host your web sitehttp://lists.sweetmarias.com/mailman/listinfo/homeroast">http://webhosting.yahoo.com/homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
My problem with my dial thermometer is that the setting "drifts" (for lack of a better term). Last week it seemed consistently 25deg high (based on its "room temperature" reading, and the reading during first crack). This week it seems about 25 deg low. Significantly annoying. =Spencer dewardh wrote: <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Spencer: <Snip> lack of a better term). There are lots of "problems" with "stick and dial" thermometers . . . but they still manage (usually) to work reliably and well. I've seen one actually "skip a tooth" on its drive gear (when being used near the top of its range) . . . "permanent" re-calibration, that . And they, like all thermometers, make certain "assumptions" about use and environment. It used to be (with glass/mercury in particular) that thermometers had on them an "immersion line" .. . . the presumption being that below the line was in whatever was being measured, above the line was at some (human compatible, unless otherwise specified) "ambient". I've seen "digital" (thermocouple/RTD) probes specified thus, but it's no longer common, and I've never seen it on an "inexpensive" instrument (although what's doing the "measuring" is pretty obvious with an exposed bead thermocouple). In fact the temperature of the upper part of the stem (and the dial, in "mechanicals") can, as in Rick's case, make a significant difference in the reading. There can be a problem with thermowells also, especially if the sample is small, the sample/environment differential is high, and the thermal conductivity of the well itself is not well attended to. I've seen probes with one TC at the tip, and another "compensating" junction further up the probe. Not cheap, though . . . usually the only "compensating junction" is in the box. Roasting, like politics and, heh, dare I say life itself? can seem simple on the surface . . . but it can get quite complex as one digs into the details. That's why we (usually) settle for "good enough" . . . (or, in politics, "not good enough, but the best we can get at the moment"). Deward homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |