EFLOW EF-Series - SECTION 4 - THE FLOW SENSOR

EF-Series Instruction Manual
Rev 2/01 4-1
SECTION 4 — THE FLOW SENSOR
4.1 SCOPE
This section describes the orifice-metering Flow Sensor (also called a DVS or Dual-Variable Sensor),
which provides differential pressure and static pressure inputs to the EF-Series flow computer for the
orifice flow calculation. Note that the Sensor is not equipped to provide a temperature input to the
flow computer; this input comes directly into the unit by means of the built-in RTD input. Refer to
Section 2.
This section contains the following information:
Information Section Page Number
Description 4.2 4-1
Process Connections 4.3 4-2
Sensor Wiring 4.4 4-2
Configuration 4.5 4-3
Calibration 4.6 4-4
Verifying Calibration 4.6.1 4-4
Calibrating the Meter Inputs 4.6.2 4-5
Zero Shift 4.6.3 4-8
Specifications 4.7 4-8
4.2 DESCRIPTION
The orifice-metering Flow Sensor measures differential pressure and static pressure by converting the
applied pressure to electrical signals and making the readings available to the Main Electronics Board.
The sensor housing screws into an adapter, which in turn mounts with four bolts to the bottom of the
EF-Series enclosure. The Sensor cable plugs directly into the Main Electronics Board at the P/DP
connector.
The readings from the Sensor are stored in analog inputs on the EF-Series Unit. The differential
pressure value uses the Analog Input (AI) Point Number A1, and the static pressure value uses the AI
Point Number A2. If the alarm for either point is enabled and the sensor fails to communicate, during
either initialization or operation, an alarm is entered in the Alarm Log.
The Sensor uses an interrupt to inform the Main Electronics Board that it is ready for an update. This
must occur at least once per second. The flow computer then converts this value and stores it in the
proper analog input for access by other functions within the unit. If an update does not occur in the
one second interval, the sensor is re-initialized. A point fail alarm is set if the sensor does not respond
to the initialization.