When you need more control over a process than simple on/off valves provide, proportional products offer an easy way to achieve that precision. Proportional regulators, sometimes called I to P or E to P valves, offer end-users a simple and reliable way to convert a control signal to a pressure. These regulators are ubiquitous in applications where tight pneumatic control is a must.
While some of these are used right out of the box with no configuration, others are tuned to perform in specific ways. For this reason, proportional regulators often get a reputation for being “more art than science” and the tuning process can seem daunting.
For simple applications where a manual regulator is being replaced by an electronic one, being field-adjustable isn’t a priority. Often, these design changes are made to eliminate human error and customers are OK with a product that isn’t customizable because precise, repeatable, output is what matters most. Something like an ED02 or ED05 series offers great value and a “plug and play” installation process.
For customers looking to customize the response of a product, field-tunable regulators are necessary. Adjustments such as changing the output range, changing the way the unit interprets the setpoint, and changing the feedback skip the lengthy process of reprogramming a PLC.
Consider an example where a customer controls the pressure of a process using an HMI but after installing a new interface, the regulator won’t respond to changes in the setpoint. By using the Data Acquisition Software, or DAS, the customer plugs into the regulator and sees that the setpoint isn’t being received in the first place. That leads them to look at the terminal strip on the back of the HMI and they discover that the setpoint and feedback wires had been swapped. Being able to look into the valve’s controller allows troubleshooting times to be cut down, which is critical when customers face potential shutdowns.
Being able to make adjustments digitally makes it easy to rapidly test solutions and eliminates the variability that comes with mechanical adjustments such as set screws or variable resistors.
The DAS software used by the Sentronic series of regulators provides key functions for tuning. The real-time scope, allows users to quickly troubleshoot behavior. This shows setpoint and output pressure, as well as the behavior of the onboard PID controller.
DAS also allows quick parameter changes on the fly. Users are able to easily invert the setpoint signal, make changes to the span and offset, and switch between Current and Voltage control. More advanced PID settings, which affect how responsive the controller is, are also adjustable. Once a set of parameters has been generated, they can be saved and loaded onto other units in a couple of mouse clicks for easy deployment and maintenance.
One final use for the DAS software is setting up a cascade control loop (sometimes called dual-loop). This allows a Sentronic series regulator to take in feedback from a downstream sensor and close a control loop around it. While a cascade control always requires tuning the PID, it is a powerful tool for applications such as controlling the force output of an actuator based on feedback from a load cell or positioning a pneumatic cylinder based on feedback from a position sensor.
These features and the DAS software are available on the direct acting Sentronic D and Sentronic PLUS as well as the pilot-operated Sentronic LP and Sentronic HD.
The post Advantages of a Tunable Proportional Regulator appeared first on the Emerson Automation Experts blog.
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