Emerson 8800A, Product Manual

Page: 38 / 160

Rosemount Model 8800C Vortex Flowmeter
2-28
Analog Output
The flowmeter provides a 4–20 mA dc isolated current output, linear
with the flow rate.
To make connections, remove the FIELD TERMINALS side cover of the
electronics housing. All power to the flowmeter is supplied over the 4–
20 mA signal wiring. Connect the wires as shown in Figure 2-22 on
page 2-30.
NOTE
Twisted pairs are required to minimize noise pickup in the 4–20 mA
signal and digital communication signal. Shielded signal wire is
preferred, but not required. To ensure communication, wiring should
be 24 AWG or larger and not exceed 5,000 ft (1500 m).
Pulse Output
NOTE
Remember when using the pulse output, all power to the flowmeter
is still supplied over the 4–20 mA signal wiring.
The flowmeter provides an isolated transistor switch-closure frequency
output signal proportional to flow, as shown in Figure 2-20. The
frequency limits are as follows:
• Maximum Frequency = 10000 Hz
• Minimum Frequency = 0.0000035 Hz (1 pulse/79 hours)
• Duty Cycle = 50%
• For Frequencies
ˆ
0.1 Hz the pulse width will equal 5 seconds
• Supply Voltage (V
s
): 5 to 30 V dc
• Load Resistance: 100
W
to 100 k
W
V
s
/0.02 amps = Ohms (typical)
V
s
/0.12 amps = Ohms (max)
• Switch Closure: Transistor, open collector
Open contact < 50
m
A leakage
Close contact < 20
W
The output may drive an externally powered electromechanical or
electronic totalizer, or may serve as a direct input to a control element.
To connect the wires, remove the FIELD TERMINALS side cover
of the electronics housing. Connect the wires as shown in Figure 2-23
and Figure 2-24 on page 2-30.