External Setpoint Function - Grundfos CRE Installation And Operating Instructions Manual

8.13 "External setpoint function"

Pump variant
CME
CRE, CRIE, CRNE, CRKE, SPKE,
MTRE
You can influence the setpoint by an external signal, either via one
of the analog inputs or, if an advanced functional module (FM 300)
is fitted, via one of the Pt100/1000 inputs.
Before you can enable the function, you must set one of
the analog inputs or Pt100/1000 inputs to "External
setpoint function".
See the sections on analog inputs and Pt100/1000 inputs.
Example with constant pressure with linear influence
Actual setpoint: actual input signal x (setpoint - sensor min.) +
sensor min.
At a sensor minimum of 0 psi, a setpoint of 232 psi and an external
setpoint of 60 %, the actual setpoint is 0.60 x (232 - 0) + 0 = 139
psi. See the figure below.
A
B
C
D
Example of setpoint influence with sensor feed back
Pos. Description
A Sensor maximum
B "Setpoint"
C Actual setpoint
D Sensor minimum
Actual input signal
E
(60 %)
F External setpoint signal
"External setpoint
function"
●
●
F
E
Example with constant curve with linear influence
Actual setpoint: actual input signal x (setpoint - user-set minimum
speed) + user-set minimum speed.
At a user-set minimum speed of 25 %, and a setpoint of 85 % and
an external setpoint of 60 %, the actual setpoint is 0.60 x (85 - 25) +
25 = 61 %. See the figure below.
A
100
B
85
C
61
D 25
0
0
0.5
0
0
0
4
-50
Example of setpoint influence with constant curve
Pos. Description
A Speed [%]
B "Setpoint"
C Actual setpoint
D User-set min. speed
E Fixed maximum speed
Actual input signal
F
(60 %)
G External setpoint signal
Related information
8.5 "Analog inputs"
8.6 "Pt100/1000 inputs"
E
G
F
100 %
3.5 V
5 V
10 V
20 mA
20 mA
204 C
45