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.
Application of interference-free circuitry to other measurements, Page 1 of 2
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