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Programming the Outputs
10.16 4-20mA outputs
4-20mA Outputs display both the loop current and
it's corresponding 0-100%.
Manual = User sets current. Auto = Sensor controls
current.
Displays the present 0% to 100% output set-point.
Manual Mode:
Use Manual mode to verify the 100% ON=20mA,
OFF=4mA or modulate operation of the proportional
pump or valve that the 4-20mA output is controlling.
Use Manual mode to verify the monitoring input that
is using the current loop value to represent a
controller conductivity, pH, ORP or corrosion rate
sensor or ppm calculation.
Load Powered 4-20mA Loop:
4-20mA current outputs are isolated and loop
powered (24VDC).
Open Loop Alarm:
The DC isolated 4-20mA output alarms on an open
loop, this function could be turn ON/OFF
Calculating Loop Current:
4-20mA Output current (mA) = 4 + 16 x ( Sensor
Value / ( 20mA Set-point – 4mA Set-point) ) Use
the absolute value of the set-point difference for
20mA Set-point < 4mA Set-point.
For example:
15.42mA = 4 + 16 ( 1785 / ( 2500 - 0))
The output card can be configured to drop to 4mA
when the stop button is pressed on the keypad
(when using to control a pump or solenoid) or to
continue if used to send sensor value to DCS.
10.16.1
How to assign 4-20mA output to
control decrease (e.g Acid Feed):
1- To Set 4-20mA output to control decrease
press MENU
2- Use Up/Down Arrows to navigate to I/O
Setup
3- Scroll to select the desired output (for
example E:4-20mA output) and press OK
and then press F2
4- Use Up/Down Arrow keys to select desired
input (here we selected pH input) then press
F1
5- The next menu will ask for interlock if any
needed. If no need, scroll to none then
Press F1 (you could interlock it with any
digital input for example flow switch or a
phantom DI)
6- Set the high pH value then press F1(in this
example if pH sensor is reading 7.7pH the 4-
20mA will be 20mA and the acid pump will
be feeding at max speed)
:
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7- Set the low pH value, then press F1(in this
example if pH sensor is reading 7.20 pH, the
4-20mA will be 4.0mA and the acid pump
should stop feeding).
8- In this example between pH 7.20=4.0mA
and 7.70=20mA the 4-20mA output will be
proportional
Press ESC Escape to finish or press F1 to
9-
continue with output setup. You can choose
to turn the open loop alarm on or off, then
choose to set the output to drop to 0%
(4mA) or
remain as is
when the
keypad STOP
button is
pressed. This
allows you to
shut down the
output to a
pump, or
continue to
send a value
to a DCS.
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