Position sensors help ensure comfortable elevator landings

11 November 2010

Spring Loaded LVDT position sensors (also known as gaging probes) supplied by Macro Sensors, are serving as integral components in a control system designed to ensure the accurate landing of elevator cars at building floors.

As passengers travel on elevators at speeds of up to 2,000 ft/min, electromechanical control systems rely on sensors to provide the necessary feedback for proper alignment of elevator cars at building floors upon arrival.

To ensure a smooth and comfortable ride, elevator cars are suspended by springs within an outer frame that provide cushioning against the effects of acceleration/deceleration and the initial starting and stopping ‘jerks’ caused by inertia. As the elevator is loaded with passengers, the springs compress changing car position within the frame that can affect final car position at the destination floor.

To ensure that both cars and building floors properly align upon arrival the spring-loaded LVDT position sensors are being used to measure the difference between the frame and car position. Specifically, the sensors are measuring 'spring deflection' as a result of the passenger load.

The, sensors can be mounted either under or above the elevator car. When measurement is made from above, the probe of the spring-loaded LVDT position is normally compressed, and extends as the load increases. When sensors are installed below the elevator platform, the probe is normally extended, and compresses as load increases. Output is fed into a control system that uses the displacement information to adjust the travel of the frame, so that when the elevator car doors open, the car floor is level with the building floor on which passengers are exiting.

Macro Sensors also offers metric calibration options for all Spring-Loaded LVDT position sensors.

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