ATI Model F12/D Gas Transmitter Part 4 – Operation
65
O&M Manual (Rev-H)
4-20mA Menu
During alarm inhibit and Auto-test, the 4-20mA output is fixed at 4.0mA (17.4mA for oxygen sensors) to
prevent false alarms at the receiver. The output is forced to 3.6mA to signal a Trouble alarm to the
receiver. These are the default values, which may be changed in the 4-20mA Menu, below.
Figure 85. 4-20mA Menu
4-20mA Adjust Menu
These methods permit adjustment of the 4-20mA output and provide a way to force it to a fixed value to
test receiver alarms. They do not affect the computed gas concentration reading.
Figure 86. 4-20mA control page
4-20mA Adjustment
Loop adjustment consists of adjusting the 4 and 20 mA levels (order does not matter) by scrolling the
corresponding DAC value. This may be accomplished by reading a calibrated current meter connected in
series with the transmitter’s 4-20mA output, reading a calibrated volt meter across a precision load
resistor in series with the transmitter’s 4-20mA output, or reading the display of a calibrated, current loop
receiver
.
Adjust 4mA Menu
Figure 87. Adjust 4mA Menu
When using a current loop receiver, make certain the reading is not limited to 20mA by hardware or programming. If
so, adjust the reading first to 19.5mA, then slowly increase it to 20.0mA.
Set the fixed output level during Auto-test (4.0 to 22.0 mA).
This is normally 4.0mA to prevent alarms at the receiver.
Set the output level to indicate alarms are not enabled (4 to 22
mA). This is normally 4.0mA to prevent alarms at the receiver.
Set the output level to indicate the Trouble alarm (3.5 to 3.8
mA). Note: 3.5mA not allowed on 2-wire 4-20mA connection.
Adjust the 4mA and 20mA levels, or force the output for testing.
Adjust the 4mA analog output level.
Adjust the 20mA analog output level.
Force the 4-20mA output to a fixed level between 3.5 and
22.0 mA. Displays the real time value when not selected.
Scroll the DAC (digital-to-analog converter) count up to increase
or down to decrease the analog output to 4.00mA.
Note
The displayed value is “as left” by the previous adjustment.
►Autotst mA= 4.0
Inhibit mA= 4.0
Trouble mA= 3.6
Adjust
Monitor the …
►DAC Count=412
…4-20mA>Adjust>Adjust 4mA
Warning:
Disable current loop receiver alarms before proceeding.
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