Gefran Introduces Safety-Certified Draw Wire Sensors for Mobile Machinery

Gefran has expanded its GSH series of draw wire sensors to be safer than ever before. Determining linear or angular position in moving machinery is essential to its safe operation. Now, Gefran's series includes draw wire sensors that are SIL2/PLd safety-certified, guaranteeing safe and reliable operation. The series expansion aims to ensure the safe operation of booms, aerial platforms, lifting systems, telehandlers, and other such machinery.

Gefran’s GSH series draw wire sensors now include SIL2 / PLd-certified versions. Image used courtesy of Gefran

What Is a Draw Wire Sensor?

A draw wire sensor is a type of linear displacement sensor. It operates on the same principle as a tape measure: one end is attached to the moving part, and the other is fixed. As the part moves away, the distance changes, uncoiling the line from the housing. Depending on the configuration, the position is measured either by changes in resistance as the line unspools or by rotational speed and direction via Hall-effect sensing.

GSH Series Draw Wire Sensors

Gefran’s GSH series draw wire sensors use Hall-effect sensing rather than resistance sensing. Hall-effect sensing is contactless, which means the GSH sensors have lower wear and lower maintenance than conventional sensors. Available in draw wire lengths from 1.8 m to 12.5 m, the sensors are designed to meet the needs of most mobile machine applications.

Two product lines are available in the GSH family: the GSH-S and GSH-A. The GSH-S is used for determining linear position changes, while the GSH-A is used for calculating linear and angular position changes.

The GSH series is available with stroke lengths ranging from 1.8 m to 12.5 m. Image used courtesy of Gefran

Communication with the GSH series sensors can be accomplished through CANopen and CANopen Safety protocols. Some models provide analog output, such as 0.5 V to 4.5 V and a standard 4 mA to 20 mA current signal. Each sensor can be ordered with a variety of common connectors, including IP67-rated connectors suitable for harsh, outdoor environments.

Safety-Certified Sensors

Typically, draw wire sensors are not known for their robustness in challenging environments. However, Gefran’s new addition of SIL2 / PLd-certified versions demonstrates that the GSH sensors can meet rigorous safety and reliability standards, particularly in environments where shock and vibration can quickly degrade uncertified sensors. Also, the new sensors can be used to support safety systems and diagnostics, such as fault detection, failure management, and forcing a system into a safe state during an excursion.

The GSH series is purpose-built for mobile machine applications in construction, agriculture, and material handling. Image used courtesy of Gefran

Mobile Machine Applications

Gefran’s new safety-certified draw wire sensors are geared towards the moving machine industry. Bucket trucks, crane booms, and other mobile machines can be controlled more safely if the operator knows exactly how far they have been extended. Due to the nature of such machinery, sensors must be rugged enough to withstand the elements so that dust, dirt, and grease do not contribute significantly to error. In particular, moving machinery in the agricultural, material handling, and construction market sectors will benefit from these sensors.