Impact Sensor: Description and Operation

INFLATABLE RESTRAINT FRONT END SENSOR
The front end sensor, also known as the electronic frontal sensor (EFS), is equipped on some vehicles to supplement SIR system performance. The EFS is an electro-mechanical sensor and is not part of the deployment loops, but instead provides an input to the SDM. The SDM uses the input from the EFS to assist in determining the severity of a frontal collision further supporting air bag deployment. If the SDM determines a deployment is warranted, the SDM will cause current to flow through the deployment loops deploying the frontal air bags.

INFLATABLE RESTRAINT SIDE IMPACT SENSORS (SIS)
The side impact sensors (SIS) contain a sensing device which monitors vehicle acceleration and velocity changes to detect side collisions that are severe enough to warrant side inflator module deployment. Each SIS is not part of the deployment loop, but instead provides an input to the SDM. The SDM contains a microprocessor that performs calculations using the measured accelerations and compares these calculations to a value stored in memory. When the generated calculations exceed the stored value, the SDM will cause current to flow through the deployment loops, deploying the side air bags.