Selectors & Sensors — Frequently Asked Questions
What is the difference between an incremental and absolute position encoder for elevator use?
An incremental encoder counts pulses from a reference point on every power-up and requires a re-homing run to establish position after a power failure. An absolute encoder stores position in non-volatile memory and knows its exact shaft location immediately on power-up, eliminating re-homing delays. Absolute encoders are preferred in high-traffic buildings where minimizing out-of-service time after a power cut is critical, and are increasingly required by premium controller manufacturers.
How does a load-weighing sensor improve energy efficiency?
Load-weighing cells installed on the car buffer or under the car sling measure actual load before departure. The controller uses this data to optimize the motor starting torque, reducing the energy spike at start-up and improving overall system efficiency by up to 8%. Additionally, the data feeds the overload protection circuit mandated by EN 81-20 §14.2.5, preventing departure when the rated load is exceeded.
What EN standard governs elevator door-safety light curtains?
EN 81-20 §7.7.3 specifies requirements for re-opening devices on power-operated doors, including light curtains. The curtain must detect an obstruction across the full door height and trigger immediate door reversal. Multi-beam 3D curtains that also detect low-height objects (such as a child's foot or a small suitcase wheel) are now considered best practice and are available from several Turkish suppliers listed on elevator.tr.
What Performance Level (PL) rating should elevator safety sensors carry?
ISO 13849-1 defines Performance Levels PL a through PL e for safety-related control functions. For most elevator safety functions (overload detection, door safety), PL c or PL d is required depending on the severity and frequency of the hazard. Always request the PL declaration and the supporting SISTEMA or PASCAL calculation from the sensor supplier to verify conformity.