Absolute and Gauge Pressure

Absolute and Gauge Pressure

Absolute and gauge pressure measurement covers pressure transmitters and pressure switches for liquids and gases in hygienic and general process services. Cerabar transmitters and Ceraphant switches are offered with hygienic approvals, and variants are available with functional-safety (SIL) and explosion-protection certifications.

Device designs are differentiated by the measuring cell and the process interface. Configurations are offered with ceramic or silicon cells, and diaphragm seals extend compatibility for challenging media and temperatures. In a silicon-cell transmitter, pressure deflects a process-isolating diaphragm and is transferred via fill fluid to a resistance bridge for electronic evaluation. Pressure switches change an electrical PNP contact at a defined setpoint and can also provide a 4–20 mA signal.

Benefits come from matching sensor physics to the duty. Silicon-cell technology supports process pressures up to 700 bar, delivers overload resistance, enables compact flush-mount connections, and minimizes thermal effects on the measurement. Diaphragm seals broaden material and process-connection options and support process temperatures from −70 to +400 °C. Switching devices add clear onsite status through LEDs and digital display, with configuration possible locally or via PC. Options for quick setup and plug‑and‑play commissioning reduce time and cost during startup.

Typical applications include pressure monitoring on pumps, compressors, filters, and reactors; alarm and interlock functions for overpressure or vacuum conditions; and hygienic skids where cleanability and approvals are mandatory. With appropriate seal construction and wetted materials, corrosive, abrasive, or high-temperature media can be accommodated. In closed vessels, pressure measurement is frequently used as an indirect level signal via hydrostatic head for stable inventory control.

Specification generally focuses on reference type (absolute versus gauge), required range and turndown, accuracy and long-term stability, maximum overpressure, and wetted-material compatibility. For difficult services, diaphragm-seal selection, fill-fluid choice, and mounting geometry influence response time and drift. Define signal type, diagnostics, and verification approach early to protect measurement integrity over the instrument lifecycle.

Engineered Equipment Company, a leading supplier of specialized industrial equipment.