Walchem WebMaster ONE Instruction Manual page 60

Alarm should be selected if the relay is to be activated based on an alarm condition.
Activate on a DI should be selected if the relay is to be activated whenever a digital input is in
either an open or a closed state.
Target PPM Feed should be selected if the relay is to be activated to feed a chemical to achieve a
PPM set point. This algorithm triggers the relay activation when a user-defined volume of makeup
water (measured by up to 3 water meters) is added to the system. The relay on-time is calculated
using the PPM set point, cycles of concentration (measured or calculated), specific gravity of the
chemical product, and programmed pump flow rate.
Target PPM Feed with Feed Verification should be selected if the relay is to be activated to feed
a chemical to achieve a PPM set point. This algorithm triggers the relay activation when a user-
defined volume of makeup water (measured by up to 3 water meters) is added to the system. The
relay on-time is calculated using the PPM set point, cycles of concentration (measured or
calculated), specific gravity of the chemical product, programmed pump volume per stroke, and
number of strokes counted by a feed verification device.
Click on the "Submit Changes" button to save the changes. This will change the Relay Input
Assignment section that comes next, making the possible choices for the input assignment match
the control mode.
Analog Output Control Mode (1 – 4)
This section will only appear if there are one or more 4-20 mA output cards installed.
Use the pull-downs to select the control mode for each analog output: Not Used or Retransmit.
Relay (1 – 8) Input Assignment
This section is where the input used to control the relay is assigned. The choices available in the
pull-down will depend upon the control mode of the relay. If you have changed the control mode
of any relay, click the Submit Changes button before selecting the input assignment.
If the relay control mode is Not Used:
The relay input assignment is Not Applicable.
If the relay control mode is On/Off Set Point, or Time Proportional:
The relay input assignment choices will be any of the sensor inputs, and any of the optional analog
inputs. Any number of relays may be assigned to the same input.
If the relay control mode is Cycles of Concentration:
The relay input assignment choices will be any of the conductivity inputs. Any number of relays
may be assigned to the same input.
If the relay control mode is Intermittent (Fixed Blowdown Time), Intermittent (Proportional
Blowdown Time):
The relay input assignment choices will be any of the sensor or analog inputs. Any number of
relays may be assigned to the same input.
If the relay control mode is Flow Based Feed, Bleed Vol on Makeup Vol, Target PPM Feed or
Target PPM Feed with Feed Verification:
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