Response Time and Lag of a Thermometer Element Mounted in a Protecting Case

In this paper equations are derived and applied for determining the response time and temperature lag, in general, of a body which exchanges heat with a medium indirectly through a second body. Application is made to a thermometer element mounted in a protecting case, with specific reference to a resistance-type thermometer such as is used for aircraft and marine purposes. The temperature distribution along the stem and the errors resulting when the head of the bulb and medium differ in temperature also are derived.