The CLS is a sensor designed to detect the presence of water in the oil chamber and is activated when the water to oil ratio surpasses a certain percentage.

Upon detecting a high concentration of water, the sensor current changes and the monitoring relay (CAS or MiniCASII) gives a leakage signal by an LED and a relay contact.
The CLS can be used to give an early warning of excessive water intrusion.
Since the detected water is contained in a buffer space there is no imminent danger.
A CLS alarm usually gives the operator some time to plan for the service.

Physical background
The sensing element consists of capacitance plates, implemented as thin bands on a flexible circuit board in the glass tube. Due to the flat orientation of the bands the electrical field emanates from one plate, passes through the glass, through the liquid and then back through the glass to the other plate.

The sensed capacitance depends on the change in dielectric characteristic of the liquid. Water and oil are significantly different in this respect.

The relative dielectric constant is 80 for water and usually 2-4 for oil.

Electrical properties
The CLS is provided with two leads for external connection. The supply voltage is 12 V DC and it is a polarised device. Therefore it is important to connect it with correct polarity.
The brown lead is plus (+) and the black is minus (-).

The CLS is designed to be used internally in the pump, placed in the bearing holder with its sensing part in the oil chamber. The sensor is intended for the type of bearing holder with threaded hole for mounting of the sensor.

When used with the MiniCAS II supervision relay, the CLS is connected in series with pump motor thermocontacts.

If an FLS sensor is also used, the FLS and CLS are connected in parallel.

Used with a CAS relay, the CLS can be connected to the A- or B-channel.
Technical data
Trip emulsion:  Approx. 35% of water in oil 
Supply voltage:  12 V DC 
Signal:  0 mA reversed polarity 
  5,5 mA non-alarm current 
  29 mA alarm current 
Poles:  2 wires, protected with a diode 
  (wrong polarity connection = 0 mA) 
Max. temperature:  90ºC, 1h 
Test temperature:  115ºC, 1h 
Max. continuous duty temperature:  70ºC 
Metal parts:  Acid proof stainless steel  
Sensor tube:  Glass 
Physical size   
-Length:  75 mm (approx.. 3 in.) 
-Diameter:  13,5 mm (.53 in.) 


Part number: 505 1200
The CLS is an electronic device and ohms measurements are useless.


An alternative is to test the CLS with the MiniCAS II relay or any other 12 V DC source, measuring the current in through the CLS. Wrong polarity will give a zero current.
Refer to the CLS/FLS/MiniCAS II Installation and application guide for additional information, part no: 892472


The CLS is sensitive to electromagnetic interference which can cause a false leakage signal. When a variable frequency drive is present in the plant, the emitted interference must be isolated not to disturb the CLS.


On suspicion of a VFD interfering with the CLS, this can be established by switching the VFD off. The CLS will then revert to non-alarm current immediately, the alarm can be reset and proper measures be taken (see the CLS/FLS/MiniCAS II Installation and application guide).