• Easy-to-use interface with user selectable flow tables
• Accepts any 4-20mA water level sensor’s input
• 4-20mA output signal for recorders or displays
• Relay outputs for alarms, sampling, or datalogging
• Water resistant enclosure

Global Water’s FC220 Open Channel Flow Monitor is a reliable and accurate instrument for measuring and totalizing open channel flows for all flumes and weirs, as well as for any gravity-type open-channel flow application.  The flow meter measures water depth using any 4-20mA water level sensor’s output including Global Water’s highly accurate 
submersible pressure transducer or 
ultrasonic water level sensor and the flow meter’s powerful microprocessor instantly calculates and displays water flow and totalizer values in user selectable units using one of several water flow calculation modes.  The Open Channel Flow Monitors have an 8-button keypad that easily guides you through the versatile setup menus.

Open Channel Flows

For any open channel that is free flowing, there is a specific relationship between depth of water and flow rate.  Whenever a given depth occurs, there will always be the same water flow.  Therefore, if the flow rate is known for each depth, a depth-to-flow relationship can be constructed.  The Open Channel Flow Monitor supports a large number of different types of flow calculation modes.  Over 40 preprogrammed flume and weir tables are included with the open channel flow meter.  For monitoring in round pipes and open rectangular channels; the water flow meter’s Manning’s Equation mode allows the user to enter their own parameters for material, slope and pipe or channel dimensions.  The open channel flow monitors also allow you to define standard flow equations, which can calculate flow for almost all flumes and weirs.  Another mode lets the user enter parameters into the water flow meter for a best fit 3rd order polynomial which is useful for calculating flow based on empirical data and lookup tables (see article on 
Stream Flow Gauging).  In addition, one (1) factory programmable lookup table can be permanently stored in the open channel flow monitor’s processor memory for monitoring in applications where a single equation can’t accurately predict flow, such as streambeds and open channels with complicated geometry.  A 16-character name can be programmed into the FC220 water flow meters by the user to identify the installation site or show other information about the configuration.

Depth Measurement

Global Water’s standard open channel flow monitors can measure flow depth with any 4-20 mA water level sensor including the highly-accurate 
WL400 Water Level Sensor, which is a fully submersible water level sensor constructed of stainless steel.  Any water level sensor range can be used with the flow meter, however a sensor with a range near to your largest expected water level changw will give you the the best accuracy.  Submersible pressure transducers should be mounted slightly below the “zero” flow depth of the open channel, upstream from the throat of the flume or weir.  For open channels with no primary device, the sensor should be mounted below the lowest expected water depth.  Because the open channel flow monitor accepts a 4-20 mA input signal it can be mounted up to 3000 feet away from the water level sensor.

Global Water also offers an 
ultrasonic water level sensor that allows the Open Channel Flow Monitor to measure semi-solid flows or flows that are not suitable for a standard submersible pressure transducer.  Global Water recommends that the ultrasonic sensor option only be used in areas where AC power is available.  You should strongly consider using a submersible pressure transducer with your open channel flow monitor for applications that are in areas without AC power.

Open Channel Flow Monitor Display

The Open Channel Flow Monitors display water flow with up to 7 digits allowing for very large flows to be displayed.  The water flow meter’s totalizer records up to 9 digits of flow volume in non-volatile memory, and is password protected from reset.  Available volume units are cubic feet, gallons, million gallons, cubic meters and liters; time units include seconds, minutes, hours and days. This allows the open channel flow meters to display flow in 20 different user defined units.  Water level is calibrated and displayed in feet, inches, meters or centimeters; and a water level offset function allows the measured water level to be adjusted to compensate for variations in the water flow meter’s sensor installation.

Open Channel Flow Monitor Output

The water flow meters have four independent relay outputs for triggering external devices like 
water samplers and monitoring devices.  The open channel flow monitor’s relays can be separately programmed to trigger based on volume per pulse, and threshold settings can be used to limit triggering to flows above preset levels.  There is also an accurate and scalable 4-20mA output provided for monitoring the flow using data loggers and PLC devices.  An internal USB data logger is available as a factory option for the open channel flow monitor to allow the historical flow data to be recorded, as well as the exact time of each relay trigger event.  Free software is provided for programming the data logger, downloading flow and relay data, and exporting to spreadsheets.  The water flow meters have programmable power saving features that allow the supply current to be reduced, which is important in remote monitoring applications.

Water Flow Meter Enclosure

The enclosure is made of weather resistant injection molded plastic.  It is suitable for use in a wide variety of environments.  The enclosure can be wall-mounted and fitted with conduit for sensor and power connections, if required.