Re: [Elecraft] Generic words on temperature
In years past, we had a spec where 60C was the the hottest temp allowable on any exposed accessible surface. On a metal surface with high thermal conductivity and significant thermal mass (e.g. aluminum heat sink), it feels very warm to the touch, only starts to cause pain after many seconds, and causes pain long before causing injury. That spec might be codified in some safety standards somewhere. A piece of wood or plastic at 60C just feel warm. Heat and temperature are very different. They have different dimensions and units. Lou W7HV On Sunday, July 4, 2021, 4:47:36 PM MDT, Francis Belliveau wrote: All, I am taking this off-list since it is so far off topic. What I said seems to have been somewhat misinterpreted. 1. "Threshold of pain" means it starts to hurt, not "I can't stand it any more". 2. The surface temperature of a child's forehead when running a fever of 106 degrees is less than 100 degrees. The 106 is an internal temperature. 3. This is a "rule of thumb", not an absolute. Run the experiment yourself: * Come up with a way to measure the temperature of a hot surface. Maybe an over window could be used, but you need to measure the surface temperature. Using a forehead thermometer will not work since it has bee calibrated to read internal temperature based on the cooler external temperature. * Heat the surface to 99 degrees and see how it feels. * Then try it again at 100 or 101 degrees. Yes, individuals can handle much hotter temperatures. I once saw somebody reach into a hot fish-frier and come out unburned; but he had been working in the frying industry for years and had built up the ability to to that. This "rule of thumb" is based on a "normal average". 73, Fran > On Jul 3, 2021, at 19:52, David Woolley wrote: > > 100°F is well within the survivable body core temperature range, so it should > never trigger pain receptors. > > In fact, I believe it was defined based on the nominal core body temperature > of a cow. > > Did you mean 100°C? > > -- > David Woolley > > > On 04/07/2021 00:03, Francis Belliveau wrote: >> Another rule of thumb for those who care. >> When you hold a finger on something and it is 10 seconds to pain threshold, >> that location is about 100 degrees F. >> This is not an absolute constant, but I have checked it a few times since I >> was told that, and it seems to be true for me. > > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to f.belliv...@comcast.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to louand...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Generic words on temperature
All, I am taking this off-list since it is so far off topic. What I said seems to have been somewhat misinterpreted. 1. "Threshold of pain" means it starts to hurt, not "I can't stand it any more". 2. The surface temperature of a child's forehead when running a fever of 106 degrees is less than 100 degrees. The 106 is an internal temperature. 3. This is a "rule of thumb", not an absolute. Run the experiment yourself: * Come up with a way to measure the temperature of a hot surface. Maybe an over window could be used, but you need to measure the surface temperature. Using a forehead thermometer will not work since it has bee calibrated to read internal temperature based on the cooler external temperature. * Heat the surface to 99 degrees and see how it feels. * Then try it again at 100 or 101 degrees. Yes, individuals can handle much hotter temperatures. I once saw somebody reach into a hot fish-frier and come out unburned; but he had been working in the frying industry for years and had built up the ability to to that. This "rule of thumb" is based on a "normal average". 73, Fran > On Jul 3, 2021, at 19:52, David Woolley wrote: > > 100°F is well within the survivable body core temperature range, so it should > never trigger pain receptors. > > In fact, I believe it was defined based on the nominal core body temperature > of a cow. > > Did you mean 100°C? > > -- > David Woolley > > > On 04/07/2021 00:03, Francis Belliveau wrote: >> Another rule of thumb for those who care. >> When you hold a finger on something and it is 10 seconds to pain threshold, >> that location is about 100 degrees F. >> This is not an absolute constant, but I have checked it a few times since I >> was told that, and it seems to be true for me. > > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to f.belliv...@comcast.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Generic words on temperature
Ahh, well, a few comments clarifications, from a guy with 38 years of experience (HVAC/mechanical and controls engineering) with Carrier air conditioning. Opening comment (not really my area of expertise, but I do have moderate relevant experience), the heat pain threshold is quite variable (between individuals, and depending on time of day and LOTS of other factors), and the touch test is probably not a reliable predictor of whether the radio is "too hot". My perception is that the Elecraft radios are thermally well protected, but if really concerned, I think measuring temp with an IR sensor and comparing it against published limits might be a preferred approach to assessing it. As to atmospheric pressure and altitude, these are really separate variables. While there is a functional relationship between them, it's not so strong that for most normal activities (i.e. unless the plan is to climb K2, Everest or similar) it shouldn't be a significant factor in the discussion. And FWIW, temp generally decreases with increasing altitude, which then of course lessens an overheating problem by increasing the heat transfer driving delta-T. As to whether it's better to install fans in a blow-thru or a draw-thru configuration, there's no clear winner for this type of electronics cooling application. If condensation was an issue (it's not), the distinction between these might become significant. Given that, the decision between these would generally be based on the mechanical layout and on related testing meant to insure that specific components remain sufficiently cool in worst case conditions. (BTW, no way one could hold his finger on a smooth 100C surface for 10 seconds, and no way that same surface at 100F would rise above the heat pain threshold in 10 sec.) Chris Jones - K2CZ On Wed, Jun 30, 2021 at 9:37 PM Geoffrey Feldman wrote: > My rule of thumb is that if you can keep your finger on it for a second or > so without pain, it's not too hot. > > > > The ambient temperature is really not the issue as much as whether heat is > carried off. I know it's hot in the pacific northwest but I think you can > still enjoy your gear. The larger issue is RFI from air conditioners. > > > > The environmental consideration many people neglect is atmospheric > pressure. > As altitude increases, there is less air to carry the heat away. People > sometimes install fans with an idea to sucking out the heat. This is > actually wrong. The fan should blow ambient air in and the venting for it > to > get out should intend that pressure inside the case be a bit higher than > the > ambient pressure. More molecules against the hot part, the better. If you > read the fine print on electronic specifications you will often (and should > always) see an atmospheric spec with the heat spec. > > > > All the above is just rule-of-thumb of course. There is a lot more to > cooling electronics than the above but I think these are worth considering. > > > > Elecraft gear is pretty good at protecting itself as well. If your radio > cuts out, it's doing its job of living for more fun later. > > > > W1GCF > > Geoff > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to cajo...@gmail.com > __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Generic words on temperature
100°F is well within the survivable body core temperature range, so it should never trigger pain receptors. In fact, I believe it was defined based on the nominal core body temperature of a cow. Did you mean 100°C? -- David Woolley On 04/07/2021 00:03, Francis Belliveau wrote: Another rule of thumb for those who care. When you hold a finger on something and it is 10 seconds to pain threshold, that location is about 100 degrees F. This is not an absolute constant, but I have checked it a few times since I was told that, and it seems to be true for me. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Generic words on temperature
Another rule of thumb for those who care. When you hold a finger on something and it is 10 seconds to pain threshold, that location is about 100 degrees F. This is not an absolute constant, but I have checked it a few times since I was told that, and it seems to be true for me. > On Jun 30, 2021, at 21:36, Geoffrey Feldman wrote: > > My rule of thumb is that if you can keep your finger on it for a second or > so without pain, it's not too hot. > > > > The ambient temperature is really not the issue as much as whether heat is > carried off. I know it's hot in the pacific northwest but I think you can > still enjoy your gear. The larger issue is RFI from air conditioners. > > > > The environmental consideration many people neglect is atmospheric pressure. > As altitude increases, there is less air to carry the heat away. People > sometimes install fans with an idea to sucking out the heat. This is > actually wrong. The fan should blow ambient air in and the venting for it to > get out should intend that pressure inside the case be a bit higher than the > ambient pressure. More molecules against the hot part, the better. If you > read the fine print on electronic specifications you will often (and should > always) see an atmospheric spec with the heat spec. > > > > All the above is just rule-of-thumb of course. There is a lot more to > cooling electronics than the above but I think these are worth considering. > > > > Elecraft gear is pretty good at protecting itself as well. If your radio > cuts out, it's doing its job of living for more fun later. > > > > W1GCF > > Geoff > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to f.belliv...@comcast.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] Generic words on temperature
My rule of thumb is that if you can keep your finger on it for a second or so without pain, it's not too hot. The ambient temperature is really not the issue as much as whether heat is carried off. I know it's hot in the pacific northwest but I think you can still enjoy your gear. The larger issue is RFI from air conditioners. The environmental consideration many people neglect is atmospheric pressure. As altitude increases, there is less air to carry the heat away. People sometimes install fans with an idea to sucking out the heat. This is actually wrong. The fan should blow ambient air in and the venting for it to get out should intend that pressure inside the case be a bit higher than the ambient pressure. More molecules against the hot part, the better. If you read the fine print on electronic specifications you will often (and should always) see an atmospheric spec with the heat spec. All the above is just rule-of-thumb of course. There is a lot more to cooling electronics than the above but I think these are worth considering. Elecraft gear is pretty good at protecting itself as well. If your radio cuts out, it's doing its job of living for more fun later. W1GCF Geoff __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
