ABSTRACT
If a physical measuring instrument is placed in an environment, its thermal response, as for all objects, will be subject to the laws of thermodynamics and it can be influenced by the combination of the air temperature, radiant temperature, humidity and air velocity around it. If the environment changes with time, then the thermal response of the instrument will lag behind the change and its response time will be important. It is of great importance, therefore, to understand the thermodynamics of the instruments that we use when considering measurement to predict human response. This is particularly important as the range of possibilities for data storage and analysis has greatly increased and it is possible to confuse sophistication with measurement performance. A compact device which simultaneously measures and records information every second or minute over a number of hours or days and transmits data for analysis, may well have great utility but the validity of the measurements will depend on the nature of the sensor and the laws of thermodynamics.
