Endress+Hauser Liquisys M CCM223 - Page 67

Liquisys M CCM223/253 Commissioning
Endress+Hauser 67
Three-point step controller
With this type of controller, you can control motorized valves for metering chlorine gas.
• If the controller activates relay 3, the motorized valve closes.
• If the controller activates relay 4, the motorized valve opens.
X
W
X < W
X > W
A
B
C
C
B
R4 mark-to-
space ratio
overdosed
underdosed
measuring signal
relay output
R3 mark-to-
space ratio
A0025217-EN
 43 Function of the three-point step controller
A Measured value is in set point window
B Measured value is smaller than the set point
C Measured value is larger than the set point
W Set point
X Measured value
• Measured value is in set point window (A)
Relays 3 and 4 are not activated. The motorized valve does not change.
• Measured value is smaller than the set point (B)
Not enough chlorine gas is metered. Relay 4 is activated (pulse control). The motorized
valve is opened further and the dosage metered is increased.
• Measured value is larger than the set point (C)
Too much chlorine gas is metered. Relay 3 is activated (pulse control). The motorized
valve is closed further and the dosage metered is reduced.