The level input in conjunction with entered dimensional parameters is used to determine the cross-sectional area of the fluid in the channel.
Several regular channels are catered for including: Rectangular, Triangular, Trapezoidal, Circular and Half-Round. Flow can be measured in other channel shapes with a Non-linear selection that allows the level input to represent the actual cross-sectional area of the fluid at various levels.
The volume calculation is based on the multiplication of the cross-sectional area and the velocity of the fluid in the channel.
Volume flow = velocity x area
The area for one of the selectable channel shapes is derived from the channel dimensions (width, base or diameter) and the input from the level sensor. For “non-linear” channels, parameters are available to allow the area to be read directly from the level input via a series of correction points.
The front panel display of the open channel flow computer shows the current values of the input variables and the results of the calculations. A list of the variables for this application and their type (total or rate) is shown at the end of this document.
The instrument can be supplied with a real-time clock for data logging of over 1000 (up to 50000) entries of the variables as displayed on the main menu.
There are two communication ports available as follows:
• RS-232 port
• RS-485 port (optional)
The ports can be used for remote data reading, printouts and for initial application loading of the open channel flow computer.
The opto-isolated outputs can re-transmit any main menu variable. The type of output is determined by the nature of the assigned variable. Totals are output as pulses and rates are output as 4-20 mA signals. One output is standard, a second output is available as an option.
The relay alarms can be assigned to any of the main menu variables of a rate type. The alarms can be fully configured including hysteresis. Two relays are standard with additional two relays available as an option.
The instrument can be further tailored to suit specific application needs including units of measurement, custom tags, second language or access levels. A distributor can configure these requirements before delivery.
Instrument parameters including units of measurement can be programmed in the field, according to the user access levels assigned to parameters by the distributor.
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