The replacement of mercury thermometers in Stevenson screens

With the withdrawal of mercury thermometers from use and sale due to a perceived health hazard, a suitable alternative is required for meteorological observations. This article looks at the possible alternatives and describes an electronic design that will simulate the response of traditional meteorological thermometers and thereby prevent a major discontinuity in the long‐term temperature and humidity records. The design also enables a simple, direct, physical exchange of thermometers using the same screen fixtures. It uses a platinum resistance thermometer as the sensor, exposed within a ‘bulb’ designed to replicate the thermal characteristics of traditional mercury thermometers. Being electrical, the measurements can also be logged automatically, allowing unattended operation.