High Temperature Effects on Ceramic-Insulated Thermocouple Wires

Conductors transmitting low voltage signals through unconditioned high temperature environments have been experimentally investigated. Measurements of insulation resistance, open-circuit voltage, and signal attenuation were taken, for several chromel-alumel, metal-sheathed, ceramic-insulated thermocouple wires at temperatures approaching 2000°F. Test results show that: insulation resistance calculations and measurements agree; signal attenuation is directly dependent upon the length of the wire; overall signal attenuation is more dependent on conductor resistance than on insulation resistance; when open circuits exist, errors are generated within thermocouple wires when the wires are heated to temperatures above 400°F.