Abstract: A gage having sensors for observing temperature and pressure. The gage includes a display and an internal computer. A data cartridge separate from the gage but with an electrical plug type connection to it is supplied. The data cartridge has a non-volatile memory on which is stored data relating pressure and saturation temperature of a volatile refrigerant. A program is stored within the gage. The program contains instructions for measuring temperature and pressure from a source, retrieving from the data cartridge saturated temperature data corresponding to the observed pressure, calculating superheat or subcooling and displaying in sequence the observed pressure in absolute or gage terms, the corresponding saturated temperature, the observed temperature and the superheat or subcooling.

Abstract: An electronic device for observing temperature and pressure and for indicating pressure, especially very low pressures. The device has a single sensor element for responding to both temperature and pressure. The device includes a sequence timer for causing the device to first observe the resistance of the sensor when the device is first turned on. The timer then applies a voltage across the sensor, causing a known current to flow through the sensor. The current heats the sensor an amount corresponding to density and therefore the pressure of the gas to which it is exposed. A calculating device is provided for calculating the temperature from the observed value of the initial sensor resistance and the pressure from the observed values of current flow and subsequent sensor resistance. A display is provided for indicating the calculated pressure.