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Page 20
Principle Operation
Section 1
The lower left corner of the Status Bar indicates whether a program is
Running, Halted, or Ready To Start. If it is not needed during a programming
step, it disappears.
The lower right corner displays system alarm conditions, such as low memory
battery. For a list of possible alarms see Section 4.4 on page 73.
The status bar also lists the valid choices when entering certain programming
information. For example, when selecting the units of level measurement from
the Level Units menu, the status bar indicates that the valid choices are:
cm, ft, in. or m.
1.5 Principle Operation
Measurement Capabilities
The 980 Flow Meter is often used to measure flow in conjunction with a
primary measuring device (flume, weir, pipe, etc.) that has a known
level-to-flow relationship. The 980 Flow Meter directly measures the level of
liquid in a channel that is contributing to flow (referred to as “head”) and
calculates the flow rate based on the head-to-flow relationship of the primary
device. (Refer to Appendix A on page 109).
The 980 Flow Meter can also simultaneously measure and record:
The AV option can also measure the average velocity of the flow stream using
a submerged Doppler probe and calculate flow based on the current level and
the formula: Wetted Area × Velocity = Flow.
Communication Capabilities
A graphical display allows fast, on-site review of historical data.
In addition to its extensive data logging capabilities, the 980 Flow Meter is
capable of:
• Enabling a sampler
• Pacing a sampler
• Controlling four external devices with Normally Open/Normally
Closed relays
• Controlling two external devices with 4–20 mA current outputs
Communications capabilities include a standard RS232 port used for data
transfer and updating internal embedded program using state-of-the-art Flash
Memory technology.
The 980 Flow Meter also provides SCADA Communication Interface
functionality using the Modbus
®
ASCII protocol. This software protocol
communicates with the instrument via an RS232 or modem connection.
• Level • Velocity (AV version only)
• pH • Temperature
• Rainfall • Seven discrete analog inputs
(voltage and/or current)