The Types 627B, 628B, and 629B are temperature controlled capacitance manometers that are much less affected by ambient temperature changes than unheated Baratrons. Heating the sensor also reduces or eliminates the possibility of process byproducts depositing inside the manometer to cause drift, which can have a significant effect on system availability and repeatability. They are available in lower full-scale pressure ranges than unheated products, which permits their use in more demanding processes. All of the models are internally regulated to their specified operating temperature; no external controllers, cables, or sensors are needed. The Types 627B and 628B operate at 450C and 1000C respectively, and have a 15-pin D-subminiature electrical connector. They also have an option for "Heater Status" and "At Temperature" LED indicators and relay contact. The Type 629B can be configured to operate at either temperature, and uses a 9-pin D-subminiature electrical connector for "drop-in" compatibility with many competitive products. The Type 629B also offers an optional external zero set capability, allowing its zero to be set remoy一 a major advantage in many process tools that do not permit easy access to the capacitance manometer. The 450C Type 627B offers full-scale pressure/vacuum ranges from 0.02 to 20,000 Torr （0.026 mbar to 26.3 bar）, and the 1000C type 628B has pressure/vacuum ranges from 0.05 to 20,000 Torr （0.066 mbar to 26.3 bar）.