Reference Port - GE K0470 User Manual

6 Reference and Specification
6.2

Reference Port

The reference port provides the negative pressure to the gauge sensor and to the barometric
reference (option). Gauge sensors use this port identified as "REF". For gauge sensors
(without a barometric reference) small pressures can be applied (Ref: Specification, Section
6-7). All other pressure measurement requires the port to be opened to atmosphere. When in
gauge mode, the instrument shows and controls the pressure difference between the
reference port and the output port.
Note: This is not a true differential operation as there is no true differential calibration of the
sensor.
The transducer of the barometric reference option senses atmospheric pressure via the
reference port, when enabled the port MUST be open to atmosphere.
The reference connection should be actively used (differential connection option) for
precision low pressure measurement. The instrument measures pressure relative to the
pressure at the reference port.
An atmospheric pressure change causes the indicator to adjust the pressure and appears at
the pressure output as apparent instability. To keep a stable controlled pressure, the
reference port should be restricted. Using a reference port restrictor (snubber), short term
ambient pressure variations can be prevented from affecting indicator performance.
The indicator and UUT references should be connected together (using the optional
differential connection kit) to provide a common reference to atmosphere.
K0470 Revision A 6 - 2 [EN] English