An enthalpy comparator for comparing the enthalpies of two bodies of air is disclosed having a first temperature sensor and a first humidity sensor for sensing the temperature and humidity respectively of the first body of air, a second temperature sensor and a second humidity sensor for sensing the temperature and humidity respectively of the second body of air, and a diaphragm module unit having a first diaphragm defined chamber connected to the first temperature sensor, a second diaphragm defined chamber connected to the second temperature sensor, a third diaphragm defined chamber connected to the first humidity sensor, and a fourth diaphragm defined chamber connected to the second humidity sensor, and an output sensing mechanism associated with the four chambers for providing an output dependent upon the enthalpies of the first and second bodies of air, and, in particular, the difference between the enthalpies of the first and second bodies of air. The areas of the diaphragms which define the first, second, third and fourth chambers are selected to yield a close approximation of the enthalpies of the two bodies of air.
展开▼
