Analogue Input Batch/Ratio Controller for Volumetric Flow Meters

The 515 BR02 application is a batching ratio controller for delivery of preset quantities at preset flowrates using a volumetric analog input. Batch control can operate in preset or on-off modes, while flow control can be set to local (manual) or PI loop mode.

This application provides the operator with clear local readout including flowrate deviation and can be controlled via communications in more automated systems. There is quick access to commonly used preset values directly from the front panel if access has been authorised.

The PI control of the process flow is via a 4-20mA proportional valve or pump controller. It has integral wind- up protection, a deadband, output hold and ramp time that can be programmed to reduce wear on valves and actuators and provide for bumpless operation.

CALCULATIONS

There are three types of control modes in which the process flow is dependent on the main flow. These are RATIO, BLEND-1 and BLEND-2 modes where the relationship between the flows are as follows:

Ratio Control Mode.
The process flow is a ratio of the main flow (0 to 400% range).

Pflow
Ratio% = —————- × 100
Mflow

Blend Control Modes.
These modes cater for blending points before and after the main flowmeter. The process flow is a ratio of the net (combined) flow (0 to 80% range).

Pflow
Ratio% = —————- × 100
Netflow