Ams trex™ Device Communicator

not
prompted to select a power
option to set the position of the valve.
4.10
Settings for controlling current
4.10.1
Change the values for the quick buttons
The 
Loop Diagnostics
screen has five buttons that have default values of 4 mA, 8 mA, 12
mA, 16 mA, and 20 mA. These buttons let you quickly change the current. You can change
the value for each button.
Loop Diagnostics application
User Guide
September 2021
144
User Guide

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Figure 4-17: Quick buttons
Procedure
1. On the 
Loop Diagnostics
screen, tap 
Trex Unit Current
→
More Options
→
Quick
Button Selection
.
More Options
does not appear unless the 
Trex Unit Power
or 
Trex Unit Current
is
enabled.
2. Tap one of the 
Quick Button Selection
options.
3. Enter a new value for the button, and tap 
OK
.
4. Repeat until all buttons are set as desired.
5. Tap 
Back
to save the changes and return to the 
Loop Diagnostics
screen.
User Guide 
Loop Diagnostics application
September 2021
User Guide 
145

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4.10.2
Change the scale for the up and down arrow keys
The 
Loop Diagnostics
screen has up and down arrow keys that let you manually adjust the
current in small increments to slowly move a valve. The default increment is 0.1 mA, but
you can adjust the scaling.
Procedure
1. On the 
Loop Diagnostics
screen, tap 
Trex Unit Current
→
More Options
→
Arrow
Scaling for mA
.
More Options
does not appear unless the 
Trex Unit Power
or 
Trex Unit Current
is
enabled.
2. Enter a value between 0.04 to 10.00 mA.
3. Tap 
OK
.
4. Tap 
Back
to save the changes and return to the Loop Diagnostics screen.
4.10.3
Set the duration to change the current
You can control how long it takes the Trex unit to change from sourcing one current value
to another. Select a higher value to gradually change the current and avoid abrupt
changes to a valve's position that may damage equipment. Select a value of zero to quickly
move a valve.
This option applies to the quick current buttons, the up and down arrow keys, and the
pencil icon that enable you to enter a new current value. It also applies when you tap 
Trex
Unit Power
to stop powering the positioner.
Note
This option does not apply to the initial current value that is applied when you first power
the device. For example, if you power a device, the Loop Diagnostics application will
immediately source 4 mA, 20 mA, or the mA value you entered. The delay applies to any
change to the current value after initial start up.
Procedure
1. On the 
Loop Diagnostics
screen, tap 
Trex Unit Current
→
More Options
→
Duration of Current Change
.
More Options
does not appear unless the 
Trex Unit Power
or 
Trex Unit Current
is
enabled.
2. Tap the desired number of seconds.
3. Tap 
OK
.
4. Tap 
Back
to save the changes and return to the Loop Diagnostics screen.