Arming Sensor

The inflatable restraint arming sensor is a protective switch. It is located in the high side (power side) of the deployment loop. The inflatable restraint arming sensor closes at low level velocity changes (lower than the inflatable restraint discriminating sensors). This ensures that the inflatable restraint steering wheel inflator module connects directly to the 36 VLR output of the inflatable restraint Diagnostic Energy Reserve Module (DERM) or Ignition 1 voltage when either of the discriminating sensors closes.
The inflatable restraint arming sensor consists of the following components:
^ A sensing element.
^ Switch contacts which are normally open.
^ A 5.1 kohm diagnostic resistor.
^ A 2.49 kohm diagnostic resistor.
^ Two diodes.

The sensing element closes the switch contacts when the velocity of the vehicle changes quickly enough to indicate a potential need for deployment.
The 5.1 kohm diagnostic resistor is connected in parallel with the switch contacts. This allows a small amount of current to flow through the deployment loop during normal operation. The current flow results in current drops across each component that is within the deployment loop. The DERM monitors these voltage drops in order to detect circuit or component malfunctions. The 2.49 kohm diagnostic resistor is connected in parallel with the diodes. This allows the DERM to monitor the voltage that is applied to the high side of the deployment loop. The two diodes that are in the inflatable restraint arming sensor isolate the 36 VLR output of the DERM from the Ignition 1 voltage.