1. On/Off vs Proportional Valves On/off valves are basically the on/off switches for hydraulic systems. On/off valves are typically used in applications where precise position or speed control are not required. Proportional valves of - fer more variable control of flow rates for hydraulic systems. These valves are typically used in applications where more control is re - quired beyond a standard directional control valve. A few applications that call for variable flow rate control where proportional valves shine include wind turbine pitch control, wood processing, machine tools, and metal forming. If specific timing and/or positioning is required, think proportional. 2. Onboard Electronics vs Offboard Electronics Determining whether a valve with onboard or offboard electronics is the best choice requires an in-depth evaluation of the application. Generally, on - board electronics are used to localize control at the valve and simplify the wiring at the controller. Offboard electronics are often utilized in areas with high vibration and temperatures that can reduce the performance of the electronics. Driving an offboard electronics valve requires use of an electronic module that can be configured to custom parameters such as desired solenoid drive current and ramp rates. Onboard electronics valves can be commanded directly with a standard command including 420 mA or ±10 VDC and flow for the same level of customization. 3. Open-Loop vs Closed-Loop Control There are two control options for hy - draulic systems: open-loop and closedloop. In general textbook terms, an open-loop system cannot compensate for any disturbances that alter the driving signal of the controller. Closedloop systems do not have this shortcoming; disturbances in the system are compensated for by measuring the output response and comparing it to the input. If there is an observed difference (known as an error signal), the error is fed back to the controller to adjust the output to the desired value. Motion Design, October 2021 Cov ToC Parker's FP Series direct operated control valves close the loop internally around the position of the spool but can be integrated into a closed-loop system. Metal forming equipment is a typical application for a proportional valve. 7http://info.hotims.com/79418-936