A NOTE ON PLATINUM/PLATINUM-RHODIUM THERMOCOUPLE UNCERTAINTY
The term uncertainty is used rather than instability. Two configurations of platinum/platinum-10% rhodium thermocouples were developed for the Tory II reactors. The manufacturer checked outputs at 2400 F. Subsequertly, tests were run between 2000 and 2400 deg F to determine how dependable the initially measured outputs were. The uncertainty turned out to be about plus or minus 10 deg F, over the rather narrow test band. As a result of these first uncertainty tests, it was decided to see what effect, if any, different types of junctions have on the uncertainty. Results are presented of tests on crimped, twisted, hydrogen-arc-welded, and resistance-welded junctions. A horizontal tube furnace was used from 1500 to 2300 deg and a vertical tube furnace from 2300 to 2800 deg F. Some unexplained things happened when the transfer to the vertical tube furnace was made. Reference grade, 10-mil thermocouple wire with alumina tube insulation was used for most tests. In general, the uncertainty showed up as an error band of fairly constant width. This meant that it could not be expressed as a percent of indicated temperature. The band width tended to become narrower with increasing temperature up to 2300 deg F or so; 20 deg F was still a good'' figure for it at 2300 deg F. The importance of an annealing cycle to test temperature is shown by the curves. Wire size definitely affects the uncertainty picture. Even 20-mil platinum/ platinum-rhodium wire has an appreciable uncertainty. A series of tests were begun using platinum resistance thermometers. These tests on 3.5- 10- 20-, and 30-mil wire should show at least a trend. Results to date are reported. (auth)
- Research Organization:
- Univ. of California, Livermore
- NSA Number:
- NSA-16-015978
- OSTI ID:
- 4795753
- Report Number(s):
- UCRL-6589
- Journal Information:
- IRE Trans. on Nuclear Sci., Journal Name: IRE Trans. on Nuclear Sci. Vol. Vol: NS-9
- Country of Publication:
- United States
- Language:
- English
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