A computerized model of vacuum thermocouple performance

Author

Levinson, H.

Author_Institution

Best Technol. Inc., Seattle, WA, USA

fYear

1990

fDate

11-14 June 1990

Firstpage

70

Lastpage

71

Abstract

Heat-flow equations for a simplified vacuum thermocouple (VTC) were computerized using a Crank-Nicholson two-step finite-difference scheme. Comparisons were made between the computer outputs and measured values for both 500-mA and 5-mA VTCs. Curve-shape studies, radiation losses, conduction losses through all imperfect vacuum, and thermal conductivity considerations are discussed. The steady-state case demonstrated strong dependence of thermal conductivity on temperature. The output performance characteristics of the 500-mA VTC are controlled principally by the thermal conductivity of the heater, whereas those of the 5-mA units are dominated by thermal conductivity of the thermocouple wire. Calculations show that, even for very low emissivity coefficients, radiation losses are substantial in the 5-mA type, which are commonly used for AC-DC transfer standards.<>

Keywords

convertors; difference equations; electrical engineering computing; heat losses; heat transfer; thermal conductivity; thermocouples; 5 mA; 500 mA; AC-DC transfer standards; Crank-Nicholson two-step finite-difference; computerized model; conduction losses; curve shape; emissivity coefficients; heat flow equations; output performance characteristics; radiation losses; thermal conductivity; vacuum thermocouple; Artificial intelligence; Cows; Equations; Integrated circuit modeling; Measurement units; Model driven engineering; Shape measurement; Temperature; Thermal conductivity; Wires;

fLanguage

English

Publisher

ieee

Conference_Titel

Precision Electromagnetic Measurements, 1990. CPEM '90 Digest., Conference on

Conference_Location

Ottawa, Ontario, Canada

Type

conf

DOI

10.1109/CPEM.1990.109927

Filename

109927