SOME EXPERIENCES WITH NOBLE-METAL, METAL-SHEATHED THERMOCOUPLES--SECOND REPORT
This report covers the period from the fall of 1960 to the present. Items discussed are: (a) effects of method of fabrication on insulation resistance, (b) comparison of beryllia, boron nitride, and thoria with maagnesia from an insulation standpoint, (c) effect of position (vertical or horizontal) on thermocouple output, (d) nomhomogeneity of constituent wires, (e) effect of wire size on stability, (f) what happens when a junction opens, and (g) how Pt 10% Rh/ Pt thermocouples act below 32 deg F. Conclusions are as follows: (a) There seems to be no best'' methnd of fabrication. (b) Boron nitride and thoria are difficult, if not impossible, to fabricate in our configurations. Beryllia is a somewhat better insulator than magnesia, but for temperatures up to 2900 deg C the improvement is not enough to justify putting up with its toxic hazard. (c) Thermocouples should always be checked and used in a horizontal position if the temperature is high enough to soften'' any of the constituents of an alloy. (d) Care must be taken to avoid such things as kinking or otherwise damaging wire. (e) The larger the wire size, the greater the stability up to a limit of 20 to 30 mils. (f) Excessive Pt 10% Rh/Pt thermocouple output may indicate an open junction. Excessive output and reversed polarity at intermediate temperatures may indicate an open junction. (g) The Pt 10% Rh/Pt thermocouple has limited use down to -150 deg F. (auth)
- Research Organization:
- California. Univ., Livermore. Lawrence Radiation Lab.
- DOE Contract Number:
- W-7405-ENG-48
- NSA Number:
- NSA-17-037401
- OSTI ID:
- 4647217
- Report Number(s):
- UCRL-7361; CONF-191-1
- Country of Publication:
- United States
- Language:
- English
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