142AA MKS Instruments Baratron Type Vacuum/Pressure Switch

The MKS Instruments 141A / 142A Baratron Type Vacuum/Pressure Switches are based on the well-known MKS Baratron capacitance manometer and are dedicated to operating an internal relay, which provides two contact closures or openings as outputs (DPDT). The 141A/142A units offer fast, accurate, and reliable protection for vacuum equipment and processes. Designed for applications where a DC signal output is not required, the relay outputs are readily interfaced with alarms, valve actuators, computers, process controllers, or other protection devices. The 142A switch operates at an internal temperature of 100 C to help minimize effluent contamination build-up.

The 141A/142A switches combine the proven MKS high-accuracy sensor with full scale ranges from 1 Torr to 25,000 Torr (0.13 to 3333 kPa) and resolution of 0.01% of full scale, together with signal conditioning and relay output circuitry within a single enclosure. The vacuum pressure switch senses the deflection of a diaphragm due to applied pressure, providing a switched output when pressure exceeds the chosen trip point. An LED provides visual "Above Set Point" indication, and facilitates adjustment of the trip point. The dual electrode design is an all metal, all welded design, thus exposing only corrosion-resistant Inconel to the process gases. This design ensures fast response to pressure transients independent of gas composition.

he 142A switch also contains circuitry and thermal housing which controls the sensor temperature at 100°C, thereby minimizing effluent build-up and effects of ambient or process temperature variations typically encountered in process environments.

The vacuum pressure switches may be wired internally for Fail-Safe operation. In this mode, the output relay will be energized when the pressure is below the trip point instead of above. Failure of key components such as the relay (open coil) or loss of power supply voltage will then cause a high pressure (alarm) condition, in addition to any over-pressure faults.