Tuned-circuit dual-mode Johnson noise thermometers

Conference · Wed Apr 01 04:00:00 EST 1992

OSTI ID:10133189

Shepard, R L; Carroll, R M; Falter, D D ^[1]; Blalock, T V; Roberts, M J ^[2]

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1. Oak Ridge National Lab., TN (United States)
2. Tennessee Univ., Knoxville, TN (United States). Dept. of Electrical Engineering

Dual-mode Johnson noise and dc resistance thermometers can be used in control systems where prompt indications of temperature changes and long-term accuracy are needed. Such a thermometer is being developed for the SP-100 space nuclear electric power system that requires temperature measurement at 1400 K in space for 10 years, of which 7 are expected to be at full reactor power. Several direct-coupled and transformer-coupled, tuned resistance-inductance-capacitance (RLC) circuits that produce a single, continuous voltage signal were evaluated for noise temperature measurement. The simple direct-coupled RLC circuit selected provides a mean-squared noise voltage that depends only on the capacitance used and the temperature of the sensor, and it is independent of the value of or changes in the sensor resistance. These circuits provide a noise signal with long-term accuracy but require integrating noise signals for a finite length of time. The four-wire resistor for the noise temperature sensor allows simultaneous dc resistance measurements to be made that provide a prompt, continuous temperature indication signal. The dc current mode is employed continuously, and a noise voltage measurement is made periodically to correct the temperature indication. The differential noise voltage preamplifier used substantially reduces electromagnetic interference (EMI) in the system. A sensor has been tested that should provide good performance ({plus_minus}1% accuracy) and long-term (10-y) reliability in space environments. Accurate noise temperature measurements were made at temperatures above 1300 K, where significant insulator shunting occurs, even though shunting does affect the dc resistance measurements and makes the system more susceptible to EMI. 14 refs.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10133189
• Report Number(s): CONF-920423--2; ON: DE92010121
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
210600
440500
47 OTHER INSTRUMENTATION
ALUMINIUM OXIDES
CONTROL SYSTEMS
DESIGN
ELECTRONIC CIRCUITS
MATERIALS
NIOBIUM
NOISE THERMOMETERS
POWER REACTORS, MOBILE, PROPULSION, PACKAGE, AND TRANSPORTABLE
SPACE POWER REACTORS
TEMPERATURE MEASUREMENT
TEMPERATURE RANGE 1000-4000 K
TESTING
THERMAL INSTRUMENTATION