An experimental investigation of thermocouple response times in static gas environments
Abstract
The output EMF of a fine-wire thermocouple element (chromel-alumel, 0.025 mm dia) has been recorded in detail after rapid electrical heating to 25 K above ambient in various gaseous environments. The EMF always decayed exponentially, thus confirming that thermocouple response in such environments may be characterized by a time constant (T). Time constants have been obtained for a variety of Pt/Pt-13%Rh elements in static gas environments. The time constant fell with increasing initial temperature differential (above 40 K) at near atmospheric pressure, and variation of T with support wire alignment indicates that this was due to convective heat transfer. For low initial differential (below 40 K), T rose with falling gas thermal conductivity but was independent of pressure above a few mmHg.
- Publication:
-
International Journal of Heat and Mass Transfer
- Pub Date:
- October 1975
- DOI:
- 10.1016/0017-9310(75)90142-8
- Bibcode:
- 1975IJHMT..18.1207G
- Keywords:
-
- Electromotive Forces;
- Gas Temperature;
- Temperature Effects;
- Thermocouples;
- Time Response;
- Convective Heat Transfer;
- High Pressure;
- Thermal Conductivity;
- Wire;
- Instrumentation and Photography