Blending or ratio control between two flows, main and process, usually needs more than a fixed setpoint, since the target ratio has to hold even as the main flow changes. The Contrec 515 CR02 Analogue Input Batch and Ratio Controller is built for this, using analogue flow inputs on both lines.
It runs as a single loop process controller, with local (manual), loop, ratio, or blend modes, and a tuning menu for setting the Proportional Band and Integral Time for the PI control algorithm. By monitoring both flows it calculates net volume flow, and operators can view the current ratio and deviation, adjusting the setpoint from the main menu if authorized.
The PI control drives a 4-20mA proportional valve or a dosing pump, with integral wind-up protection, and a programmable deadband and output ramp time to reduce wear on valves and actuators for smoother operation.
It supports three control relationships: Ratio mode, where process flow is a percentage of main flow (0-400% range); and two Blend modes, for blending points before and after the main flowmeter, where process flow is a percentage of the combined net flow (0-80% range).
Before we quote this, we would normally check your main and process flowmeter signal types, your target ratio or blend range, and your valve or dosing pump control signal.
Hope this helps.
