Pressure-Rated Inductive Sensors Add Security in Mobile Equipment

Manufacturers of mobile equipment have long understood the benefits of replacing mechanical switches with the non-contacting technology of inductive sensors.  Inductive sensors provide wear-free position feedback in a sealed housing suitable for demanding environments.  But some applications may require a different approach if potential mounting issues or sensing ranges are a concern.  For instance, as the mobile machine ages and bushings wear due to typical daily operations, the sensing air gap between the linkage to be sensed and the sensor face may increase beyond the sensor’s optimum working range.   If this scenario is possible, periodic maintenance will be required to adjust the sensor mounting to compensate for the increasing wear.  Another consideration is the mounting bracket itself, and the likelihood of misalignment due to physical contact.

Many off road applications requiring sensor feedback involve hydraulic cylinders.  If these cases, a pressure-rated inductive sensor installed inside a cylinder or valve may be the better design choice.  Pressure-rated inductive sensors are offered with a variety of discrete outputs with numerous housing styles and connections.  Utilizing non-contact switching, stainless steel housings, and sealed to pressures up to 500 Bar, the sensors are designed to provide reliable feedback under the harsh conditions of off highway applications.

Mounting a pressure-rated inductive sensor into a cylinder or valve is straightforward, and very similar to the preparation of a hydraulic port:

      1. the sensor is threaded into the cylinder wall
      2. the sensing air gap is set
      3. the provided nut locks down the sensor
      4. a cable or connector is attached.

Day-to-day wear of the machine no longer affects the sensing gap and the sensor benefits from the additional protection of being installed into the cylinder, avoiding mounting mishaps and is better protected from external damage.

An outrigger application is a good example of the added benefits of using a pressure-rated inductive sensor.  Outriggers are used in cranes, firetrucks, aerial devices, and other mobile machines to provide lateral stability.  Mechanical switches and standard inductive sensors are used to denote when the outrigger is fully raised, lowered, etc.  A standard external sensor will do a good job as long as the mounting is intact and the sensing gap is within the proper range.  But a pressure-rated inductive sensor mounted internally into the hydraulic cylinder takes the worry out of those potential failure scenarios.

Applications with locking cylinders should also be considered.  Many locking cylinder applications are associated with a safety feature, where feedback that the cylinder is locked is critical.  An example would be the rear hatch of a refuse truck.  Occasionally, a worker may need to get inside the rear of a refuse truck.  With the rear hatch raised hydraulically, there’s a possibility that the rear hatch closes with gravity.  Positive feedback that the cylinder is locked is reassuring.

Therefore to reduce downtime caused by wear, to eliminate the misalignment of a mounting bracket, or to ensure your locking cylinder is absolutely locked, consider going “internal” to increase the quality and security of your application.

Robert has worked in the mobile equipment market for over 30 years and has educated and trained thousands of others in the operation and installation of electro-hydraulic systems. Robert has experience with mobile control systems, electronic joysticks, and a variety of sensor technologies used in the Construction, Agriculture, and Specialty Vehicle Industries.

Leave a Reply