142A Baratron

General performance switches
The 142A Absolute Ambient Pressure/Vacuum Switch offers fast, accurate, and reliable protection for vacuum equipment and processes.

The 142 is a 100°C heated manometer designed to help minimize process effluent buildup that can occur in LPCVD nitride, aluminum etch, and other types of processes. The 142A has relay outputs that are easily interfaced with alarms, valve actuators, computers, process controllers, and other protection devices.

Key features

  • Heated to minimize process effluent buildup
  • Fully adjustable set point for flexibility
  • All-metal, all-welded construction exposes only Inconel® and stainless steel for corrosion resistance
  • Fast response switching – 20 msec

Baratron Capacitance Manometer Technology

Capacitance manometers are electro-mechanical gauges that can measure both pressure and vacuum. The capacitance gauge translates a pressure-modulated movement in a thin diaphragm into an electrical signal proportional to the pressure. The pressure sensor is the thin diaphragm that is exposed to the pressure or vacuum being measured via the inlet tube. An electrode is mounted in the reference cavity behind the diaphragm. Pressure differences between the process and the reference cavity deflect the diaphragm slightly, changing the distance between it and the electrode. Variations in this distance produce variations in the capacitance between the diaphragm and the electrode creating an electrical signal that is proportional to the pressure change. Since differences in the capacitance signal are produced by physical changes within the manometer and not by changes in the gas properties, pressure measurements by the capacitance manometer are independent of the composition of the gas being measured.

Fully Adjustable Set Point

The high accuracy set point can be adjusted from from 0.2% to 100% of Full Scale for tripping the switches relay. An LED provides visual ”above set point” indication, and facilitates adjustment of the set point.

Inconel and Stainless Steel Construction

The dual electrode sensor is an all-metal, all-welded design, thus exposing only corrosion-resistant Inconel and stainless steel to the process gases.

Absolute Pressure Switching

The 141A and 142A pressure switches are referenced to vacuum for absolute pressure trip point switching. Applications for absolute pressure switches include soft pumping, gas box switching, and safety interlocks.

DPDT Relay

A double pole double throw relay rated at 2 amps @ 30 VDC or 1 amp @ 120 VAC resistive provides the set point switching. The relay is energized when pressure is above set point. Fail-safe operation provides for the relay to be energized when pressure is below set point.

Internally Heated to 100°C

These capacitance manometers are internally heated for improved accuracy. Unheated versions are exposed to ambient temperature variations which can degrade the sensor accuracy. These devices have the sensor enclosed in a volume that is maintained at a constant temperature above ambient. This solution improves the manometer’s accuracy and repeatability and lowers instrument drift by reducing or eliminating process contamination within the manometer. Heated manometers are recommended for applications that require maximum accuracy and repeatability, operate above ambient temperature and for those processes that employ hot gases.

KRISTIAN FLODSTRÖM Product specialist Vacuum technology 010-155 03 11