Importance of Sensors and Position Sensing
Numerous automated machinery and equipment applications that use pneumatic cylinders also utilize sensors to detect the linear position of the piston, position feedback, and travel within a given operation. Depending on where a sensor or switch is mounted, the sensor can detect extension, retraction, or individual positions along the cylinder body.
Accurate positioning is incredibly important for all motion applications; extension and retraction that are over or under the set parameters can cause lost time in adjustments at best, and machine or product damage at worst. Sensors and switches can offer quick, easy insights on equipment performance and even tie into predictive maintenance/Industry 4.0 initiatives. A proper sensor helps users monitor, configure, control, and maintain their machines better than machines without these components.
Reed and Solid-State Switches are the most common types of discrete position sensors. The switch is activated as a magnet attached to the actuator rod passes the sensor. They are available in two convenient mounting styles, band or track mounted – the style you choose depends on the actuator being used and user preference. Each offers its own unique benefits that allows the user to balance price, performance, and other features to their applications.
Reed switches contain a pair of flexible metal strips (known as reeds) encased in a glass vacuum that will flex to open or close when in the proximity of a magnetic field. This allows a switch mounted on a cylinder body to indicate “on” and “off” as the piston actuates.
This physical contact of a reed design provides low cost and long mechanical life; depending on the load placed on the reeds, switch life can extend into the billions of operations. On the flipside, the accuracy of reed switches can be lower than solid-state models due to larger magnetic fields, slow moving parts, or a variety of other factors. All of this can lead to less precise positioning information in the long run.
Reed Switches:
- Lower cost
- Optional integrated LED
- AC or DC options
- Compact in size
- Straight or 90° take out
- Quick disconnect or flying lead cable ends
- Track or band mounted
Solid-state switches similarly utilize magnetic fields, but without moving parts. A solid-state switch employs variations in voltage caused by the proximity of magnetic fields to detect piston positioning. Thanks to their solid-state (no moving part) design, they operate extremely well in high-speed applications and have virtually infinite service life. High-tech solid-state switches can detect the very edge of magnetic fields, reducing hysteresis and improving overall repeatability.
The biggest downside to solid-state switches is their constant, small current draw; due to this, they can only be utilized in low voltage and DC current applications.
Solid State Switches:
- Solid state reliability
- Faster response times
- Integrated LED
- Compact in size
- Straight or 90° take out
- Quick disconnect or flying lead cable ends
- Reverse polarity and over-voltage protection
- Track or band mounted
Many OEMS offer actuators with built-in linear position sensor. These sensors provide a continuous out signal that is proportional to the position of the rod. The farther the rod extends, the greater the current or voltage provided by the sensor. This continuous output allows users to pair their actuator with a proportional valve to provide precise control of the actuator throughout its stroke.
Linear Position Sensors:
- Continuous output
- Precise control over the actuator
- Contained within the actuator for improved durability
- Preinstalled at the factory
Control and diagnostic systems often pair with sensors and switches to provide a fuller analytic profile of a given machine. They can utilize a combination of hardware, software, and connected sensors to provide thorough insights on machine behavior and performance.
Want to find out what kind of switch or sensor is right for your application? Speak to one of our experts today to learn more!