System 450™ Series Modular Control Systems with Standard Control Modules Technical Bulletin
23
The Output Deadband feature can be used in conjunction with the Output Update Rate feature, but care must be
taken when selecting these values for your control system. In process loops where the condition (temperature,
pressure, or humidity) value can change quickly over a large range, the delay in updating the actual output signal
strength can cause the controlled equipment to oscillate out of range and drive the process away from the desired
setpoint. After selecting new Output Update Rate and Output Deadband values, observe your controlled system
through several cycles to determine the affect of the new values. If the calculated output signal strength is 0 or
100%, the actual output signal strength changes immediately.
High Input Signal Selection
The High Input Signal Selection feature enables a System 450 control system to monitor a condition (temperature,
pressure, or humidity) with two or three sensors (of the same type) and control relay and analog outputs based on
the highest condition value sensed by the two or three referenced sensors.
When Sn-1 and Sn-2 are set up with the same Sensor Type, the functional High Input Signal Selection sensor (HI-
2) is available for selection when you set up the outputs in the control system. When Sn-1, Sn-2, and Sn-3 are set
up with the same Sensor Type, the functional sensor (HI-3) is also available for selection.
Note: Setting up Sn-1 and Sn-2 as the same Sensor Types also enables the functional Differential Control sensor
(Sn-d). See Differential Control
for more information.
High Input Signal Selection control application examples include:
• fan-staging control on multi-circuit condensing units
• fan motor speed control on multi-circuit condensing units
Figure 9: Graph Showing Calculated Output Signal Strength and
Output Signal Strength Constrained by Output Signal Deadband
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