ROTRONIC PF4 - Manual (Page 26)

E-M-PF4-V1_00
Rotronic AG
Bassersdorf, Switzerland
Document Code Unit
PF4 Differential Pressure Transmitter:
Instruction Manual
Instruction Manual
Document Type
Page 26 of 54
Document Title
© 2014; Rotronic AG E-M-PF4-V1_00
6 Operation
This chapter describes handling of the device in operation.
6.1 Differential Pressure
6.1.1 Ambient Pressure
The differential pressure sensor in the device is dependent on the local absolute ambient atmospheric pressure
P
abs
. This must be communicated to the PF4 per display or HW4 software in order to attain the measuring
accuracy named in the data sheet. P
abs
can be determined with a barometer.
Note:
The "atmospheric pressure at the place of use" QFE is to be used and not the "normalized atmospheric
pressure" QFF , which is communicated in weather forecasts (see also http://de.wikipedia.org/wiki/QFE#QFE).
The ambient pressure enters the measurement as follows and the differential pressure is compensated
automatically on the basis of the ambient pressure setting:
Formula Legend
∆ ∆
1000
∆ Real differential pressure [Pa]
∆ Measured differential pressure [Pa]
Ambient pressure [hPa]
Relationship between altitude and pressure (on average):
Formula: 1
ö
.
where 1013.25