Rockwell Automation 1746-NR4 SLC RTD/Resistance Input Module User Manual - Manual (Page 97)

Publication 1746-UM008B-EN-P - December 2006
Ladder Programming Examples 97
Invoke Autocalibration Autocalibration of a channel occurs whenever:
• a channel first becomes enabled.
• when a change is made to its input type, filter frequency, or
excitation current.
• whenever an operating channel is disabled and re-enabled using
its enable bit.
Referring to Programming to Monitor Channel Status on page 96, you
can command your module to perform an autocalibration cycle by
disabling a channel, waiting for the status bit to change state (1…0),
and then re-enabling that channel.
This ladder diagram show you how to command the RTD module to
perform an autocalibration of channel 0. The RTD module is in slot 3.
TIP
To maintain system accuracy we recommend that you
periodically perform an autocalibration cycle at these times.
• Whenever an event occurs that greatly changes the internal
temperature of the control cabinet, such as opening or closing its
door
• At a convenient time when the system is not making product, such
as during a shift change.
ATTENTION
Several channel cycles are required to perform an
autocalibration and it is important to remember that during
autocalibration the module is not converting input data.