Signal Outputs; Current Signal Output - Grundfos DMX 221 Manual Del Usuario

Setting the dosing controller position
During the start-up operation, the dosing controller can be set
according to the operating conditions.
flow
2 mm
Fig. 17 Setting the dosing controller
1. Place the sensor at the top.
2. Set the desired stroke length.
3. Switch the pump to continuous operation.
4. Move the sensor down until "flow" starts flashing in the
display.
5. Move the sensor down another 2 mm. Otherwise very slight
deviations may be incorrectly interpreted as an error.
The dosing controller can only be used if the stroke
length remains constant during operation. Otherwise
Note
it will emit an incorrect signal.
After start-up operation
If, after 40 continuous strokes, the dosing controller does not emit
a signal, this is recognised as an error:
• The error signal relay switches on, but the pump is not
switched off.
• The LED flashes red.
• "flow" and "ERROR" flash in the display.
Manual
120
Stop
ERROR
flow
Fig. 18 Display: flow error detected
Once the error has been corrected,
• press the "Start/Stop" button to acknowledge the error.
– The error signal relay switches off.
– The pump returns to the state it was in before the error
occurred.
16
Sensor
1/min

8.5 Signal outputs

The electronics has the following signal outputs, e.g. in order to
return a signal to the control room.

8.5.1 Current signal output

To use the control signal output,
Note
see section 8.7.5 Current input -
There is a risk that the connected evaluation unit
could be destroyed!
If the unit connected to the current output has a
GND-PE reference, the current output may increase
Caution
to a multiple of 20 mA!
If this is the case, connect an isolating amplifier
between the current output and the unit.
The current stroke frequency of the pump is output as a current
signal.
• Current control 0-20 mA in mode "current output 0-20 mA"
• Current control 4-20 mA in mode "current output 4-20 mA" and
in manual mode.
The current output is linear between 4 (0) mA at
stroke frequency = 0 and 20 mA at maximum stroke
Note
frequency of the pump. The current output cannot be
weighted.
8.5.2 Error signal
Used to return various error states to the control room.
8.5.3 Stroke signal / pre-empty signal
Depending on the relay setting, the contact output emits a signal
in these cases:
• for each complete stroke of the pump, or
• a pre-empty signal input.
To set the relay, see section 8.8.1 Modifying the switch
assignment.
weighting.