Chapter 6
Ladder Programming Examples
6–11
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 Figure 6.10, you can command your module to perform an
autocalibration cycle by disabling a channel, waiting for the status bit to
change state (1 to 0), and then re–enabling that channel.
To maintain system accuracy we recommend that you periodically perform
an autocalibration cycle, for example:
•
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.
Example – Command the RTD module to perform an autocalibration of
channel 0. The RTD module is in slot 3.
Figure 6.10
Programming to Invoke Autocalibration
] [
Condition for
Autocalibration
I:1
1
Rung 2:0
Channel 0 Enable
B3
0
[OSR]
(U)
O:3.0
11
Channel 0 Flag
(L)
B3
1
]/[
Channel 0 Status
I:3.4
11
Rung 2:1
Channel 0 Enable
B3
1
] [
(L)
O:3.0
11
Channel 0 Flag
(U)
B3
1
Channel 0 Flag
Invoking Autocalibration
Tip
Summary of Contents for SLC 500 1746-NR4
Page 1: ...User Manual SLC 500t RTD Resistance Input Module Cat No 1746 NR4 Allen Bradley AB Spares ...
Page 15: ...Preface P 8 Notes AB Spares ...
Page 37: ...Chapter 2 Quick Start 2 12 Notes AB Spares ...
Page 63: ...Chapter 4 Preliminary Operating Considerations 4 12 Notes AB Spares ...
Page 87: ...Chapter 5 Channel Configuration Data and Status 5 24 Notes AB Spares ...
Page 107: ...Chapter 7 Module Diagnostics and Troubleshooting 7 8 Notes AB Spares ...
Page 117: ...Chapter 8 Application Examples 8 10 Notes AB Spares ...
Page 123: ...Appendix A Specifications A 6 Notes AB Spares ...
Page 125: ...Appendix B RTD Standards B 2 Notes AB Spares ...
