FCO432 Users Guide Issue 1
Page 29
Applications
Measuring Direct Pressure
The 400 Series Pressure transmitters can be used to measure differential pressure, output a
digital/analogue signal and display the measured pressure value. For this function, it is necessary
to select the minimum and maximum differential pressure that you need the output to be scaled
over and the pressure units that are required for the display.
The scale can be any pressure within the maximum range of the FCO432.
Example:
Using the FCO432 to measure the draft suction in a flue stack. The normal pressure is -5mb but
the FCO432 needs to be able to indicate pressures from +1mb to -16mb. A Model 4 FCO432 is
selected which has a maximum differential pressure range of 25mb.
The desired scaling is +1 to -16mb (4 to 20mA). As the FCO432 has differential pressure ports,
the suction can be applied to the -ve pressure port. The display can now be ranged for
-1 to +16mb, so ensuring the minimum pressure is less than the maximum pressure.
Set the
Display
mode to
standard
Set the
Units
to
mb
Set
DP Low
to
-1.0
Set
DP High
to
16.0
To display the pressure at a different resolution other than the FCO432 default, the display
scaling can be entered manually:
Set the
Display
mode to
Custom
Set the
Units
to
mb
Set
DP Low
to
-1.0
Set
DP High
to
16.0
Set the
Custom Units
to
mb
Set the
Decimal Point
position to
00.00
Set
Display Low
to
-1.00
Set
Display High
to
16.00
Caution:
In this mode, the display is controlled from the
Display Low
and
Display High
settings
and is not calculated from the selected engineering units.
