Gauge, Absolute or Differential Pressure?

Gauge pressure uses an atmospheric reference

Gauge pressure expresses the difference from atmospheric pressure. It is commonly used when the process requirement is written relative to the surrounding atmosphere. Include the word gauge or an unambiguous unit convention in the purchase specification. If a process operates below atmospheric pressure, state the required negative range as well.

Absolute pressure uses a vacuum reference

Absolute pressure uses an absolute vacuum as its reference rather than the local atmosphere. A numerically similar gauge range is therefore not an equivalent replacement. For a replacement instrument, check the original data sheet and full model code. The WESIVO 780T lists gauge and absolute options that must be distinguished when ordering.

Differential pressure compares two points

A differential transmitter measures the difference between its high and low sides. Applications may involve filter pressure drop or another engineered two-point measurement. Specify both differential range and line static pressure. Review the WESIVO 730E or 780C documentation for the selected configuration instead of deriving static-pressure capability from the differential span.

Remove ambiguity from the inquiry

Write the pressure reference beside every range, identify all pressure connections and state whether reverse differential pressure or vacuum can occur. For an existing system, send a nameplate photograph and a simple piping sketch. This makes it possible to review the measurement principle before selecting materials, output and installation accessories.