I my previous job as a IC engine development engineer we used platinum RTDs (also called PRTs) for most water and air temperatures (<200°C), but thermocouples for all exhaust temperatures (>500°C) where errors of 1-2°C don't really matter.
While platinum RTDs are best, they are several times the price of thermocouples, and in many cases will not be rated for operation at the higher (500°C +) temperatures that are of interest for these new NiH LENR reactors. Platinum RTDs are much more essential for accurate low temperature differential calorimetry that requires long term stability, but even then for shorter experiments a thermocouple can work OK as long as you calibrate them before or after the experiment. A cheap thermocouple with error of 1-2°C is OK for an amateur experiment measuring reactor temperatures that are in the range 4-700°C and where it is probably not worth using expensive RTDs to measure with high accuracy because other sources of error will likely be far greater than the thermocouple inaccuracy; in most cases the temperature will not be used for low temperature difference calorimetry and the temperature will vary throughout the reactor anyway. For a low cost high pressure and high temperature amateur experiment it is far better to spend money on making the reactor and hydrogen system safe than on high temperature RTDs. On 1 February 2012 15:05, Jones Beene <[email protected]> wrote: > This is bad practice ! (and it is not a small point). Often > “thermocouple” is used generically.**** > > ** ** > > Thermocouples are NOT adequate for this kind of measurement, in the long > term. They are cheaper but degrade too easily.**** > > ** ** > > For reliable measurement of hydrogen at higher temps - you should use > RTDs. They are more expensive but can be exposed to almost anything and > maintain accuracy.**** > > * * > > Typically RTDs are platinum on the exterior. See the Wiki entry.**** > > * * > > * * > > **Ø **** ** > > **Ø **This is a standard industrial technique, though it is slower to > respond than having the thermocouple exposed directly to the hydrogen in > the reactor. **** > > ** ** > > ** ** > > ** ** >
