Xylem FC220 OPEN CHANNEL FLOW MONITOR - Manual (Page 9)

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V. Sensor Input
The FC220 accepts any water level sensor with a 4-20mA, 0-5VDC or 0-1VDC output.
Available power for the sensor depends on the power input to the FC220. When
powering the FC220 from 12 volts, the sensor power is also 12 volts. If you are
running from a power supply of 18-24 volts, the sensor power can be selected from
either a regulated 12 volt supply, or directly from the 18-24 volt input. The power can
also be connected continuously or it can be set to be turned on and off by the FC220
when using power saving mode. In this mode the sensor is turned on at user defined
intervals for a programmable warm-up time, then turned off again to conserve power.
VI. 4-20mA Output
A 4-20mA output is provided that is proportional to water flow. This allows the water
flow history to be recorded by an external data logger or PLC, or by the internal data
logger option, or both. The output is scalable and allows the user to select the flow
rates that are proportional to the 4mA and 20mA output currents.
VII. Relay Operation
Four independently programmable relays are provided for triggering external devices.
These outputs are generally intended for triggering water samplers when doing flow
proportional sampling, or for recording by an external data logger or PLC. The relays
are single pole double throw (SPDT) types with common, normally open and normally
closed contacts available at the terminal block inside the FC220. The setup menu
allows the user to independently set the volume of water per output pulse, and set a
threshold level that inhibits the accumulation of volume when the flow is below a user
defined flow rate. The relays are pulsed on for 1 second when the volume of water
since the last pulse equals the volume per pulse setting, and the flow rate is above the
threshold level. Example: The volume per pulse is set to 100 gallons and the
threshold setting is 10 gallons per minute. As long as the flow rate is 10 gallons per
minute (GPM) or more, the water volume is counted and one pulse will occur for
every 10 gallons. If the flow falls below 10 GPM the counting of water volume will
stop until the flow rises above the threshold setting again. If the flow is above 10
GPM long enough to accumulate 5 gallons, then falls below 10GPM, counting stops
but the accumulated 5 gallons is retained. When the flow rate rises above 10GPM
again, only 5 more gallons is needed to output a relay pulse.