the invention relates to metallummantelte electric thermocouples at high temperatures exhibit great stability

摘要

1280674 Thermocouples JOHNSON MATTHEY & CO Ltd 22 April 1970 [12 May 1969] 24409/69 Heading H1K A sheath enclosing a thermocouple and containing a non-oxidizing atmosphere, is made from a metal selected to at least reduce the transfer of the constituent of the limbs having the greatest volatility from one limb to the other. The thermocouple limbs may comprise wires insulated by powdered magnesia or beryllia and the sheath filled with argon. A getter of Ti, Zr or Ta may be included. In order to prevent the concentration of the most volatile constituent in the limbs varying to a detremental extent the concentration of that constituent in the sheath is lower than in the limbs. For example the positive limb may be Pt 30% Rh, the negative limb Pt 6% Rh and the sheath Pt 5% Rh. Dispersion strengthened Pt may be used as a sheath which absorbs Rh, Ir, Ru, or Mo. The use of Ir and Rh 40% Ir with a Rh sheath, Pt 10-13% Rh and Pt 1% Rh or pure Pt with a Pt sheath, Pt 10% Ir and Pt with a Pt sheath, and dilute Mo-Pt or dilute Ru-Pt alloys with a Pt sheath are mentioned.