4220 Flow Meter
Section 5 Options and Accessories
5-5
mation from the flow meter to a variable analog output current
ranging from 4 to 20 milliamperes. When a condition measured
by the flow meter is converted into an analog output, 4 mA
becomes the 0% or baseline for the condition, while 20 mA
becomes the 100% or full-scale of the condition. Teledyne Isco
offers two different arrangements for providing the 4-20 mA
outputs. One is an external box that converts the signals from
the flow meter to a 4-20 mA current loop. The other is an internal
circuit board containing from one to three separate analog output
circuits on the same board.
The 4 to 20 mA current is an industrial standard current loop for
process control equipment that must respond to changing condi-
tions by varying output rates.
5.3.1 External Analog
Output Interface
The External 4-20 mA Output Interface has its own case and AC
power supply. Commercial power (120 VAC) must be available
for this device. Battery operation (12 VDC) is not feasible due to
voltage and current demands. It comes with a line cord, con-
nectors, and two interconnect cables. One cable has 6-pin M/S
connectors on both ends. This cable connects the input of the 4-20
mA Output Interface to the flow meter Interrogator connector.
The other cable has a three-pin plug on it that connects to the
output connector of the 4-20 mA Output Interface. This cable
ends in three pigtailed wires you connect to the equipment you
want to control with the 4-20 mA Output Interface.
Table 5-1 4-20 mA Output Interface Specifications
Power 120 VAC
1⁄8 Amp.
Output Connector 3-pin male plug
Pin A: + current out
Pin B: – current out
Pin C: not used
Output Accuracy:
At 72° F (22°C)
Full Oper. Range
±0.25% of full-scale
±0.5% of full scale
Operating Temperature Range 0° to 140°F (–18° to 60°C)
Resolution 0.1% of full-scale
Input Connector 6-pin male M/S
Pin B: – pulse input
Pin F: + pulse input
Pins A, C, D, E: NC
Isolation Output current optically isolated from
flow meter.
Fusing
1⁄4 Amp. internal on AC line.