This chapter discussed the other measurements with the application of interference-free circuitry. Resistance thermometry is the most precise method of measuring temperature in the range from 30 to 1000 K. The sensor is usually a compact resistor of platinum (or platinum-rhodium alloy for higher temperatures), whose value at ambient temperatures is about 25 or 100 Ω. The change of resistance with temperature is about 0.4% per Kelvin, so that measurement of the resistance to 1 ppm yields temperature with a resolution of about 0.25 mK. A given thermometer can be calibrated at the various 'fixed points', which are the melting or triple points of water and various metals, and a temperature scale derived from interpolation between these. It also shows the superconducting cryogenic current comparator, Josephson voltage source and accurate voltage measurement. There are many new and exciting possibilities for applying the higher-frequency techniques described in the previous chapters, and we now indicate only a few examples of the key future directions of this technology.

Chapter Contents:

• 10.1 Resistance thermometry (DC and low-frequency AC)
• 10.1.1 DC resistance thermometry
• 10.1.2 AC resistance thermometry
• 10.2 Superconducting cryogenic current comparator
• 10.2.1 Determining the DC ratio of two resistances R 1/R 2
• 10.3 Josephson voltage sources and accurate voltage measurement
• 10.4 Future directions
• 10.4.1 Higher-frequency measurements of quantum Hall resistance
• 10.4.2 Comparing calculable resistance standards up to 100 MHz with finite-element models
• 10.4.3 Radiofrequency and microwave measurements of carbon nanotubes and graphene
• References

Inspec keywords: voltage measurement; coaxial cables; resistors; superconducting junction devices; cryogenic electronics; comparators (circuits); temperature sensors; thermometers

Other keywords: sensor; high-frequency techniques; superconducting cryogenic current comparator; temperature measurement; interference-free circuitry; temperature 30 K to 1000 K; Josephson voltage source; resistance thermometry; compact resistor; voltage measurement; coaxial electrical circuits; interference-free measurements

Subjects: Sensing devices and transducers