Rockwell Automation 1771-TCM,D17716.5.108 TEMPERATURE CONTROL MOD - Manual (Page 34)

Chapter
4
4-1
Configuring the Module
This chapter shows you how to independently configure each PID loop of
the 1771-TCM module. This includes:
block identification
thermocouple break detection
thermal runaway detection
alarm dead band
inferred decimal point
the configuration block
The first word of each block contains a block identification code that you
use to tell the module that it is a configuration block and that you use to
tell the module which loop the block is to configure.
In the dynamic block (for loop 1, bit 1 of word 2) you can select to have a
loop operate in automatic mode. However, if a thermocouple wire breaks,
the loop would run away if left in automatic mode. Therefore, the module
provides thermocouple break detection. With bits 1 and 2 of word 2 of the
configuration block, you select a mode to which the loop is to switch when
a thermocouple wire break is detected in automatic mode.
The selections are:
disable the PID loop by forcing the CV value to zero
set the output to the TC-break forced CV value (set in word 9)
set the output to the manual-mode CV value
The values you enter into words 22 and 23 establish a maximum rate of
change in the PV temperature input value that you will allow. The
temperature change value you enter in word 22 divided by the period value
you enter in word 23 is the thermal runaway rate. With bits 4 and 5 of
word 2 of the configuration block, you select a mode to which the loop is
to switch when it detects that the rate of change of the PV temperature has
reached the thermal runaway rate. The selections are:
disable the PID loop by forcing the CV value to zero
set the output to the thermal runaway forced CV value (set in word 10)
set the output to the manual-mode CV value
Chapter Objectives
Block Identification
Thermocouple Break
Detection
Thermal Runaway Detection