Cable Extension Linear Position Sensors

Cable extension linear position sensors are used to measure the movement and displacement of objects. A cable is attached to the movable object, and, as the object moves, the transducer produces an electrical signal proportional to the cable's linear extension. Typically cable extension transducers contain a cylindrical spool that turns as the cable reels and unreels. The spool is coupled to the shaft of a rotational sensor. As the transducer's cable extends along with the movable object, it causes the spool and sensor shafts to rotate. The rotating shaft creates an electrical signal proportional to the cable's linear extension. Velocity output is available on some models as well.

The most important specification for cable extension linear position sensors is the linear range that the device is required to measure. Also important is the maximum usable range of the sensor. This is the absolute maximum range over which the device can provide sensible readings, even if it is nonlinear. Accuracy is measured as a percentage of the full scale of measurement.

Two technology types are standard for cable extension linear position sensors. Usually these devices will have either a potentiometer or an optical encoder attached to the shaft. These different technologies can produce a number of types of outputs. Analog outputs include current, voltage or a frequency. Digital outputs can include serial, parallel or other digital such as TTL output. Another option is that the output can be an alarm or a change in state of switches.

The packaging of cable extension linear position sensors is important to consider. Sometimes a sensor element with no external packaging or signal conditioning is available. More common is a transducer, a more complex device with packaging and/or signal conditioning and provides an output such as dc volts, 4-20mA, etc. Instruments and meters are often available. These are usually self-contained units that provide an output locally at or near the device. These usually also include signal processing or conditioning. A gauge or indicator is a device with a local readout and no electrical output. Recorders and totalizers are available as well for collecting and storing data locally.

• Position Sensors and Position-Sensing Instruments
  Position sensors include wide range of sensors, switches and technologies that are used to determine the placement, speed or movement, direction, and location of a given target. Linear position...
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