Walchem W900 Series Instruction Manual

Also see for W900 Series: Troubleshooting guide Instruction manual Quick programming guide Instruction manual

Contents

Walchem W900 Series Instruction Manual Manual pdf 90 page image

85Accumulator Volume Enter the volume through the flow meter with the relay deactivated.Blend Volume Enter the volume through the flow meter with the relay activated.Flow Input Select the flowmeter input to be used to control this output.Disturbance Input Select the virtual input or analog output to be used to multiplied by the control setpoint(Blend Volume).5.3.25 Relay Output, Flow Meter Ratio Control ModeFlow Meter Ratio Control Mode is typically used in cooling water applications to control the conductivity ofthe water using volumetric cycles of concentration. The controller measures the volume of makeup water goingthrough one or two water meters, and after a programmable amount, activates the relay to control a programmablevolume out through one or two bleed water meters.Output DetailsThe details for this type of output include the relay on/off state, HOA mode or Interlock status, Accumulated make-up water total, bleed cycle volume, remaining volume, relay on-time for this cycle, accumulated on-time, alarmsrelated to this output, relay type, and the current control mode setting.SettingsTouch the Settings icon to view or change the settings related to the relay.Accumulator Volume Enter the volume through the makeup water meters that will activate the relay.Bleed Volume Enter the volume through the bleed water meters that will deactivate the relay.Makeup Meter Select the makeup water meter from the pulldown list.Makeup Meter 2 Select the makeup water meter from the pulldown list, if applicable, or leave at None.Bleed Meter Select the bleed water meter from the pulldown list.Bleed Meter 2 Select the bleed water meter from the pulldown list, if applicable, or leave at None.5.3.26 Relay or Analog Output, Disturbance Variable Control ModeOnly available for 4-20 mA and pulse relay output channels.These control modes generate an output by combining contributions from a Primary control output, a DisturbanceInput, and a Trigger Input in a variety of ways. When the disturbance trigger discrete input is active, the distur-bance input is multiplied by the primary output to determine the control percent output. An alternate calculationtrigger mode selection (Use Disturbance) is available to simply switch to the disturbance output when the trigger isactive (rather than combine the two values).As a future enhancement, the Primary Output and any outputs that are used as alternate control outputs will beVirtual Outputs. For now, these will require a physical output that are not connected to any controlled devices.Some Example ApplicationsIn-Line pH Control Adjusted for FlowDirect feedback pH control in a pipe using a Primary Output of PID or Proportional control mode, with the Dis-turbance Input using flow rate to provide a multiplier to adjust the output. This is primary feedback control with afeedforward trim. No Trigger is required.Chemical feed in proportion to Flow Adjusted for pHIf the incoming flow is variable but the pH of the water is relatively constant, feed the chemical using Flow Propor-tional control mode, with the Disturbance Input using the pH reading to provide a multiplier to adjust the output.This is primary feedforward control with a feedback trim. No Trigger is required.