4210 Flow Meter
Section 4 Optional Equipment
4-5
4.4 4 to 20 mA (Analog)
Outputs (External and
Internal)
These outputs provide connection between a 4210 Flow Meter
and non-Isco process-control equipment, such as chlorinators, or
any other type of equipment that you can control with a 4-20 mil-
liampere current loop. Analog outputs convert digital infor-
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. 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.
Figure 4-1 4-20 mA Output Interface
4.4.1 Connecting the 4-20
mA Output Interface
The 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, connectors, 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 con-
nector 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.
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