Data Sheet for Product

Technical Instructions SW 141 Differential Static Airflow Switches
Document Number 155-052P25
June 17, 2010
Page 4 Siemens Industry, Inc.
Pressure Sensors
Pressure sensor selection is based on the medium to be measured, the measurement
type (static or velocity), and the required range and accuracy.
Pressure sensors measure the difference between two sensing ports usually labeled high
and low. This provides a pressure measurement against a reference. Measuring the
pressure inside a pipe or duct and comparing it to the air outside (ambient) the pipe or
duct is an example of static pressure measurement. A sensor measuring the pressure
differential across a pump or chiller measures velocity pressure.
Figure 4. Pitot Tube (Part Number 269-062).
Wiring Diagrams
Before setpoint pressure is applied to the diaphragm, the switch contact is in a normally
closed position as shown in Figures 5 and 6.
.
Figure 5. Manual Reset Switch 141-0575.
Figure 6. Auto Reset Switches 141-0518 and 141-0574.
SPDT terminals are marked Common (C), Normally Open (NO), and Normally
Closed (NC).
Figure 7. Auto Reset Switches to Prove Excessive Airflow or Pressure.