The 275 MKS Granville Phillips convectron pressure measurement gauge tube sensor is the industry standard convection-enhanced Pirani gauge. The MKS Granville Phillips 275 measures vacuum pressure from atmosphere to 1x10^-4 Torr and are ideal for roughing and foreline pressure measurement. It provides reliable fast response measurement, in milliseconds rather than seconds as in the case with thermocouple-type gauges. The high accuracy of the MKS Granville Phillips 275 Convectron vacuum gauge sensor and repeatablilty help insure that processes start at the desired pressure time-after-time. However, they are sensitive to the chemical composition of the gases being measured and are termed a relative pressure measurement method, that is, they determine the pressure indirectly from the thermal conductivity property of the gas medium. (MKS Granville Phillips 375 Convectron Controller shown in photographs is not avaliable and is replaced with the MKS Granville Phillips 475).