Impact Sensors
Discriminating SensorsThere are two supplemental restraint discriminating sensors in the Supplemental Restraint System (SRS). These are the LH forward supplemental restraint discriminating sensor and the RH forward supplemental restraint discriminating sensor. They are wired in parallel on the low side (ground side) of the deployment loop. These sensors close when the velocity of the vehicle changes severely enough to indicate a potential need for deployment.
The supplemental restraint discriminating sensors consist of the following components:
^ A sensing element
^ Switch contacts which are normally open
^ A diagnostic resistor
Arming Sensor
The sensing element closes the switch contacts when the velocity of the vehicle changes severely enough to warrant deployment. A diagnostic resistor is connected in parallel with the switch contacts. These contacts are located within each of the supplemental restraint discriminating sensors. The parallel resistors supply a ground path for a current. This current passes through the deployment loop during normal operation. The current flow results in drops in voltage across each component within the deployment loop. The supplemental restraint Diagnostic Energy Reserve Module (DERM) monitors these voltage drops in order to detect circuit or component malfunctions.
The supplemental restraint arming sensor is a protective switch. It is located in the high side (power side) of the deployment loop. The supplemental restraint arming sensor closes at low level velocity changes (lower than the supplemental restraint discriminating sensors). This ensures that the supplemental restraint steering wheel inflator module connects directly to the 36 VLR output of the supplemental restraint Diagnostic Energy Reserve Module (DERM) or Ignition 1 voltage when either of the discriminating sensors closes.
The supplemental restraint arming sensor consists of the following components:
^ A sensing element
^ Switch contacts which are normally open
^ A 5.1 kohms diagnostic resistor
^ A 2.49 kohms 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 kohms 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 kohms 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 supplemental restraint arming sensor isolate the 36 VLR output of the DERM from the Ignition 1 voltage.