Spectrum Controls 1794sc-IF8IU - Manual (Page 39)

Chapter 3: Configuring the 1794sc-IF8IU for ControlLogix/CompactLogix 3-13
User's Manual Pub. 0300231‐01 Rev. A
3.4.8 Low Alarm Threshold [Words 9,12,15,18,21,24,27,30]
Low alarm threshold setting for channels 0 through 7, respectively.
Note: The data range is determined by the data format selected.
3.4.9 High Alarm Threshold [Words 10,13,16,19,22,25,28,31]
High alarm threshold setting for channels 0 through 7, respectively.
Note: The data range is determined by the data format selected.
3.4.10 User Alarm Deadband [Words 11,14,17,20,23,26,29,32]
The deadband is a range through which the measured input may be varied without
initiating and alarm response. The deadband setting must adhere to the following rules:
• The deadband must be greater or equal to zero.
• The deadband cannot exceed 25% of full scale.
• The alarm limits including deadband may not exceed the user range limits.
• The low alarm including deadband may not overlap the high alarm including
deadband.
If any of these rules are violated, a configuration error is declared, and the alarm is
disabled. The notable exception is when the “low” is equal to the “high” and both are set
to zero. In this case, user alarms are disabled, the deadband is ignored, and no fault is
declared.
Note: The data range is determined by the data format selected.
The alarm deadband allows the user to define hysteresis for alarms. The alarm set
threshold may differ from the alarm clear threshold, depending on the deadband, as
illustrated below. A value must transition through the indicated threshold (see dashed
arrows) to have the indicated effect.
If a CJC format is selected, the alarm limits apply to that CJC format, not to that
channel’s analog input.
3.4.11 Calibration Offset [Words 33 to 40]
The calibration offset value is added to the channel data value. This value may be up to
+/- 20% of full scale for the selected range and format or a configuration error will be
declared.
E.G. +/-10V EU
Normal Dead Band Dead Band High Alarm Low Alarm
Low Alarm Threshold (Set)
Low Alarm Threshold + deadband
(Clear)
High Alarm Threshold – deadband
(Clear)
High Alarm Threshold (Set)
Figure 3-3 (Alarm DeadBand)