Rockwell Automation 1771-TCM,D17716.5.108 TEMPERATURE CONTROL MOD - Manual (Page 35)

Configuring the Module
Chapter 4
4-2
Once the temperature alarm bits are on, they are kept on until the
temperature drops below the high alarm by the alarm dead-band value or
rise above the low alarm by this value. This dead band provides a
hysteresis effect. The dead-band value applies to all alarm values.
Low Alarm With Dead Band — When the temperature falls below
the user-defined low alarm value, the low alarm bit is turned on . When
the temperature rises above the level of the low alarm value but still
below the level of the dead-band value, the low alarm bit remains on.
Only when the temperature rises above the dead-band level will the
alarm bit be turned off.
High Alarm With Dead Band — When the temperature rises above
the user-defined high alarm value, the high alarm bit is turned on.
When the temperature falls below the level of the high alarm value but
still above the level of the dead-band value, the high alarm bit remains
on. Only when the temperature falls below the dead-band level will the
alarm bit be turned off.
High Alarm Limit
Low Alarm Limit
Time Time
Input Channel
alarm on
The temperature passes thru
the dead band before the alarm
is turned on to provide stability
to alarm indicators
without deadĆband with dead-band
alarm off
dead-band
deadĆband
For words 4 thru 20, you enter a 16-bit signed integer value. However, as
you enter the value you must be aware of an inferred decimal point.
For these values in words 4 and 7 thru 14, the inferred decimal point is 2
places from the right (causing the resolution to be 0.01).
For the temperature values in words 5, 6, and 17 thru 20, the inferred
decimal point is 1 place from the right (causing the resolution to be 0.1).
Also, for each of these values, the range is dependant upon the type of
thermocouple used. The range for each type of thermocouple is
specified in appendix A.
Alarm Dead Band
Inferred Decimal Point