Arming Sensor

The arming sensor is a protective switch located in the power feed side (positive side) of the deployment loop. It is calibrated to close at low-level velocity changes (lower than discriminating sensors). This ensures inflator module is connected directly to the 36-Volt Loop Reserve (36VLR) output of the Diagnostic Energy Reserve Module (DERM) and ignition voltage when either discriminating sensor closes.

The arming sensor consists of a sensing element, normally open switch contacts, a diagnostic resistor and 2 diodes. The sensing element closes the normally open switch contacts when the velocity of the vehicle changes at a rate indicating potential need for deployment. The diagnostic resistor is connected parallel with the normally open switch contacts and allows for a small amount of current flow through the deployment loop during normal non-deployment conditions. This small current flow results in voltage drops across each component within the loop.

The DERM monitors these voltage drops to detect circuit or component faults. The 2 diodes provide isolation between the 36VLR output of the DERM and ignition voltage. In some models, the arming sensor is combined with the passenger compartment discriminating sensor and is referred to as a dual sensor. On models with dual air bags, this component is referred to as the dual pole arming sensor and provides the same function.