On 2/13/2011 12:41 PM, John Thornton wrote: > I'm measuring the cabinet temperature of a smoker with a range of 100F - > 350F and internal food temperatures from 40F to 250F or so. The > thermocouples I'm using are Auber Instruments smoker and meat > thermocouples. All the temperature devices are in the same Arduino Uno > enclosure except for the thermocouples which are in the smoker cabinet. > From some discussion on the IRC a while ago the 4052 mux with the 6075 > (just because of package) seem to be the best fit ATM for me. > > Thanks > John >
John: [Intermingling top posting (as you seem to be doing) and bottom posting (as I'm doing here) makes for confusing messages, so I've deleted the previously quoted material.] It looks like Auber sells mostly type-K thermocouples. Looking up the NIST type-K reference table, which is referenced to 32 deg-F, I see the following values. Temp Thermoelectric voltage (deg-F) (millivolts) 32 0.000 40 0.176 68 0.798 100 1.521 250 4.965 350 7.207 If your reference junction is at room temperature (let's assume it to be 68 deg-F), then for the temperatures you mention, your multiplexer and digitizer have to deal with thermocouple voltages from -0.622 mV to 6.409 mV. Looking again at the reference table, the sensitivity of a type-K thermocouple is roughly 23 microvolts/deg-F in the temperature range you're interested in. These design parameters aren't pushing the state of the art, but they do require attention in your implementation. Possibly the most important point, which is mentioned in the application note, is making sure that you have an isothermal environment at the mux connection block and that both this block and the mux and digitizer are in thermal equilibrium. I'll be interested to hear what you finally choose and how it works. Regards, Kent ------------------------------------------------------------------------------ The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE: Pinpoint memory and threading errors before they happen. Find and fix more than 250 security defects in the development cycle. Locate bottlenecks in serial and parallel code that limit performance. http://p.sf.net/sfu/intel-dev2devfeb _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
