Absolute and Gauge Pressure

Absolute and Gauge Pressure

Absolute and gauge pressure measurement encompasses pressure transmitters and pressure switches for continuous measurement and discrete switching in liquids and gases. Gauge pressure references ambient atmospheric pressure; absolute pressure uses a sealed reference, avoiding barometric influence. Cerabar sensors and Ceraphant switches are described as providing safe measurement across varied applications, including hygienic approvals and options aligned to SIL and explosion protection.

At the sensing level, pressure is converted into an electrical signal through a defined mechanical‑to‑electrical transfer. In a silicon cell, operating pressure deflects a process isolating diaphragm and a fill fluid transfers the pressure to a resistance bridge (semiconductor technology); the pressure‑dependent change in bridge output voltage is measured and evaluated. In a switch, a PNP contact opens or closes at a set pressure and a 4–20 mA output can also be available.

Technology and process-interface choices tailor performance to pressure range, temperature, and media. Silicon‑cell devices are cited for process pressures up to 700 bar, small flush‑mount process connections, overload resistance, and minimal thermal effects. Diaphragm seals expand the range of materials and process connections and enable process temperatures from −70 to +400 °C, supporting difficult fluids and demanding thermal conditions.

These capabilities translate into reliable measurement where drift, plugging, or material attack can compromise basic instruments. Continuous pressure measurement supports stable control and protection functions, while switching points provide deterministic interlocks and permissives. Pressure devices are also commonly applied for indirect level measurement via hydrostatic head; level monitoring in food applications is explicitly referenced for Cerabar/Ceraphant devices.

Typical applications include pump and compressor discharge monitoring, filter and strainer supervision, vessel and reactor pressure control, and vacuum or gas‑blanketing duties where absolute measurement improves stability. Practical operation is supported by switch features such as function checks and on‑device information via LEDs and digital displays, plus optional PC-based operation/visualization; quick setup and plug‑and‑play commissioning reduces time and cost.

Instrumentation and Controls., an exclusive authorized representative of sales and service for Endress+Hauser.