Operation
Liquisys M CPM223/253
38
Hauser
5.4.3
Current input
With the "Current input" function group, you can monitor process parameters and use these for
feedforward control. For this purpose, you must connect the current output of an external measured
variable (e.g. flowmeter) to the 4 ... 20 mA input of the transmitter. The following assignment
applies:
Monitoring of flow in main stream
This arrangement is particularly practical if the sample flow through a flow assembly in an open
outlet is completely independent of the flow in the main stream.
This permits signalling of an alarm condition in the main stream (flow too low or has completely
stopped) and triggers dosing switch-off even if the medium flow is retained due to the method of
installation.
Flow in main stream
Current signal in mA
Current input signal in
%
Current input lower range
limit
Flowmeter lower setting
value
4
0
Current input upper range
limit
Flowmeter upper setting
value
20
100
C07-CPM2x3xx-05-06-00-xx-001.eps
Fig. 32:
Alarm signalling and dosing switch-off by the main stream
A
B
C
D
E
Flow in main stream
Relay contacts of PID controller
Alarm relay
Flow below switch-off limit Z 4 or flow failure
Flow alarm
F
Z2
Z3
0
1
Flow restoration
Delay for controller switch-off, see field Z2
Delay for controller switch-up, see field Z3
Off
On
A
E
D
F
C
B
1
0
0
0
1
1
Z2
Z3