Hach sc200 User Manual page 39

• Pulse Width Modulation Control Function (refer to
Option Description
Set mode Auto—the relay output works as a PID controller.
Manual—the signal is controlled by the user through manual adjustment of the % change
value. This option is shown as Manual Output after the manual set mode is selected.
Phase Reverses the leading sign of the control deviation for the PID controller (default: Reverse). The
phase selects whether the relay will operate at the first part of a cycle (direct phase) or the
second part (reverse phase).
Set setpoint Creates a setpoint value.
Dead zone The range above and below the setpoint. In this set range, the PID controller does not take
action to change the Pulse Width Modulation On/Off Ratio output signal until the limits of the
dead zone are reached.
Period Sets the cycle duration of the PWM output signal (default: 5 seconds).
Min width Sets the minimum PWM ratio (default: 1.0 second).
Max width Sets the maximum PWM ratio (default: 4.0 seconds).
Prop band Sets the proportional part of the PID controller. The proportional part of the controller supplies
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 for disturbances.
Integral Sets the integral part of the PID controller (default: 000 minutes). The integration part of the
controller supplies an output signal. The output signal increases linearly if the control deviation
is constant. The integration part responds slower than the proportional part and can completely
compensate disturbances. The higher the integration part, the slower it responds. If the
integration part is set too low, it starts to oscillate.
Figure 24 Pulse Width Modulation function (linear mode)
1 High alarm
2 Deadband
3 Setpoint
4 Low alarm
Figure 24)
5 Period
6 Time (x-axis)
7 Phase
8 Selected source (y-axis)
English 37