External Setpoint Function - Grundfos CRE Notice D'installation Et De Fonctionnement

7.13 "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".
Analog inputs"
See sections 7.5 "
Pt100/1000 inputs"
7.6 "
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 fig. 59.
Sensor
maximum
"Setpoint"
Actual
setpoint
Sensor
minimum
Fig. 59 Example of setpoint influence with sensor feed back
"External setpoint
function"
●
●
and
.
External
Actual
setpoint
input
signal
signal
(60 %)
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 fig. 60.
Speed [%]
100
"Setpoint"
85
Actual
61
setpoint
User-set
25
min.
speed 0
Actual
0
0.5
input
0
signal
0
0
(60 %)
4
-50
Fig. 60 Example of setpoint influence with constant curve
7.13.1 "Setpoint influence" functions
You can select these functions:
"Not active".
•
When set to "Not active", the setpoint is not influenced from
any external function.
• "Linear function".
The setpoint is influenced linearly from 0 to 100 %. See fig. 61.
"Setpoint influence" [%]
100
0
0
0.5
0
0
0
4
-50
Fig. 61 "Linear function"
Fixed
maximum
speed
External
100 %
3.5 V
setpoint
5 V
signal
10 V
20 mA
20 mA
204 C
External
100 %
3.5 V
input
5 V
10 V
20 mA
20 mA
204 C
45