| Abstract | The paper describes a low-power barometer intended for remote weather stations, but also meeting the requirements for manned stations and airports, in which the condensation temperature of carbon disulphide (CS 2 ) is used to determine the barometric pressure (p) . A heated cylindrical bulb with a re-entrant well for a thermistor through the bottom and an internal radiation shield is 1/3 filled with CS 2 . Helical springs assist CS 2 migration on wetted surfaces and allow liquid and vapor to pass one another in the small diameter exit-condenser tube. A miniature Dewar flask gives thermal insulation and a 0.01-mm beryllium-copper diaphragm transmits the external pressure. The condensation temperature is read with a simple Wheatstone bridge and dc amplifier giving an output V_{0} = 0.5(p- 100 Pa) V. Pulsed power with the pulse length controlled by a second thermistor on the outlet tube is used for efficiency. Long term tests of a number of barometers have given power levels around 40 mW at 20\deg C and indicated maximum drifts of \pm50 Pa/year, \pml0 Pa/day, and \pm2 Pa short term. |
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