Hach SC4500 User Manual page 36

Option
Error list
Process event
Transfer
Timer on delay
Timer off delay
Relay contact
status
Pulse width control function
Option Description
Mode Automatic—The relay output works as a PID (Proportional, Integral, Derivative) controller.
Manual—The relay output has got an on/off ratio as set in the Manual output.
High alarm Sets the process value which leads the PWM ratio to 100% (Duty cycle set to Direct
control).
Low alarm Sets the process value which leads the PWM ratio to 0% (Duty cycle set to Direct control).
Manual output Additionally the on/off ratio can be set (condition: Mode is set to Manual). Note that this ratio
cannot exceed a value beyond the values set in the Minimum and Maximum menus.
Phase Reverses the leading sign of the control deviation for the PID controller.
Minimum Sets the minimum pulse ratio.
Maximum Sets the maximum pulse ratio.
Relay setpoint Sets the process value which is controlled by the PID controller.
Dead zone The dead zone is a band around the setpoint. In this band the PID controller does not
change the PWM on/off ratio output signal. This band is determined as setpoint +/- dead
zone. The dead zone stabilizes the PID controlled system which have a tendency to
oscillate.
Periode time Sets the cycle duration of the pulse output signal.
Minimum Sets the minimum PWM ratio.
Maximum Sets the maximum PWM.
Duty cycle Sets the status of PWM ratio.
Proportional Sets the proportional part of the PID controller.
The proportional part of the controller generates an output signal which is linearly dependent
to the control deviation. The proportional part reacts on any changes at the input but starts
to oscillate easily if the value is set high. The proportional part cannot completely
compensate disturbances.
34 English
Description
Sets the monitoring of the internal error bits of the selected source. Enabled:
Monitoring is active. Disabled (default): Monitoring is not active.
Sets the monitoring of the internal process event bits of the selected source. Enabled:
Monitoring is active. Disabled (default): Monitoring is not active.
Sets the status of the relay. Options: Relay is energized or Relays are de-energized.
(default) if some or all conditions (this means warning, error or process event bits) are
detected in the selected source or if the source is missing.
Sets a delay time for the relay to set ON.
Sets a delay time for the relay to set OFF.
Displays and logs the status of the relay contact (ON or OFF).