Hanna Instruments HI520 - Page 92

Control Modes & Algorithms 92
Dead band minimizes noise influence on control output near Set point.
SP
Relay out
Control period
Dead Band
Process value
Deviation
Proportional control
mode Low
Relay out with
Dead Band
On
Off
On
Off
Figure 36: Proportional Control, Relay Out, Proportional Control Mode Low with Dead Band
Proportional Control Interaction with Controller Status
Function / Mode Control Output
Relay Assigned to
Set Point Control Output
Analog Output Assigned to
Set Point Control Output
Hold
Measure
0 to 100 % "On"
from Control Period
"On" for the time
control output is On
Scaled value of control output
Start up 0 % Off Scaled value of control output
Hold 0 % Off
Scaled value of last control output
or a fixed value of control output
Alarm* 0 % Off
Scaled value of control output
or 22 mA, if option configured
Cleaning 0 % Off
Scaled value of last control output
or a fixed value of control output
Edit 0 % Off
Scaled value of last control output
or a fixed value of control output
Calibration 0 % Off
Scaled value of last control output
or a fixed value of control output
Manual 0 % On or Off Any value in range 0 to 22 mA
Error 0 % Off Scaled value of control output
* Controlled parameter alarms, overtime control alarms, probe disconnected