What is a Cable Extension Transducer?

A cable extension transducer has many names; string pot, draw wire sensor, string encoder, cable actuated position sensor and more...

All of these terms are used to describe a type of position sensor which is used to measure linear position through the use of a flexible cable and a string loaded spool.

The body of the cable extension transducer must be mounted to a fixed surface and the cable (usually stainless steel) is attached to the moving object. As this object moves an electric signal is produced which is proportional to the linear extension of the cable. The signal will then be sent to a display or data acquisition system so that the user has access to the information.

How do Cable Extension Transducers Work?

There are four main parts to a cable extension transducer; a measuring cable, a spool, a spring and a rotational sensor. The cable is wound around the spool inside a housing, one end is attached to a movable object outside of the sensor housing. The spool is attached to both the rotational sensor and the spring. As the cable moves, the spool rotates which in turn causes the rotational sensor to rotate. This creates an electrical signal which is proportional to the cables linear extension. The spring maintains the tension so that the cable can retract when the object moves back into the original position.

Different applications may require different output signals. The cable extension transducers we can supply can offer the following output signals;

·         Potentiometric (Voltage Divider)

·         0...10 Volts DC

·         4...20 mA (2-wire)

·         0...20 mA (3-wire)

·         CANbus J1939

·         RS232/RS422 Communications

·         Incremental Encoder (Quadrature)

·         Absolute Encoder (ask factory)

·         DeviceNET® 

Measurement ranges are another factor to consider when choosing the right cable extension transducer for your application. We have cable extension transducers which offer full stroke ranges from as small as 0-2 inches and up to 0 – 1700inches or 140ft. Make sure you contact us to discuss your application, we would be more than happy to help you select the right cable extension transducer for your needs.

What are the Advantages of Using a Cable Extension Transducer?

Cable extension transducers are often used because they have the following advantages;

·         Easy to use

·         Quick installation

·         Fit into tight spaces

·         Don’t require perfect parallel alignment

·         Have a small size to measurement ratio

·         Lower cost than some alternatives

All of our cable extension transducers are shown on our cable extension transducers page. Please contact us for more information or to discuss your application on 01327 351004 or sales@variohm.com or you can use the live chat tool at the right-hand side of the screen.