Operating Principle - ABB CM-ENS Betriebs- Und Montageanleitung

II Functions diagrams
Maximum filling level
Minimum filling level
Reference electrode C
Control supply voltage
Relay contact emptying
Relay contact filling
Function ON-delay
Function OFF-delay
Relay contact alarm AL1
Relay contact alarm AL2
The CM-ENS (A), (B), (C), and CM-ENN (D)
liquid level relays can also be operated
with 2 electrodes C and MAX only. In this
case the output relay will be energized/de-
energize around the filling level MAX.
The products CM-ENS (A), (B), (C), and CM-ENN (E) can be casca-
ded, i.e. it is possible to interconnect all electrodes as required.
Relay AL1 Contact closed
Relay AL2 Contact closed
Relay AL1 Contact open
Relay AL2 Contact open
Relay AL1 + AL2 Contact closed
NOTICE CM-ENN (D):
In case of use in low resistive conducting liquids asymmetries
may occur causing a DC voltage offset of several mV. For fur-
ther technical information, see our catalog.
LEDs
OFF Alarm electrode not wetted
OFF Alarm electrode wetted
ON Alarm electrode wetted
ON Alarm electrode not wetted
OFF Failure of control supply voltage

Operating principle

The CM-ENS/CM-ENN monitors the filling levels of conductive li-
quids. The measuring principle is based on a change in resistance
recorded by one-pole electrodes. Electrodes are connected to
C, AL1, MIN, MAX, AL2. When starting up, set the potentiometer
"sens." to the minimum value. CM-ENN (D) set "time value" at
minimum, select delay on operate function. Select suitable resi-
stance range (sector).
Preselection of the response sensitivity in the range of 5 k , 50
k , and 500 k is done by the preselection switch "sens.-sector".
The set value corresponds to the maximum range value.
Fine adjustment of the response sensitivity is done by the setting
potentiometer "sens." (sensitivity). To do this, the following scale
conversion factors referring to the range selection "sens.- sector"
have to be applied: 5 k x 0.1, 50 k x 1 and 500 k x 10.
With CM-ENS (B) and CM-ENN (E) select function DOWN.
After wetting electrodes C and MAX turn sensitivity potentiometer
"sens." towards the maximum value until the relay energizes.The
relay de-energizes as soon as the electrodes MAX and MIN are
no longer wetted.
Only CM-ENN (D): the maximum electrode level MAX is exceeded
by ON-delay A Ta 0.1-10 s. Taking the level beyond the electrode
IN is achieved by OFF-delay B Tr 0.1-10 s.
Only CM-ENN (E): When the alarm electrodes AL1 and AL2 are
wetted the output relay RAL1 energizes and RAL2 de-energizes.
Only CM-ENS (B) and CM-ENN (E): The function filling and emp-
tying control of tanks is selected by function UP (filling) and DOWN
(emptying). After a failure of the control supply voltage and at a
filling level between the level electrodes MAX and MIN the tank
will be filled. That means at selected function "DOWN" the output
remains de-energized and at the selected function "UP" the output
relay energizes at return of the control supply voltage.
English
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