CPE-KNI JOLA floor electrode

Description

The CPE-KNI JOLA floor electrode signals via an electrode relay the presence of a liquid medium due to, for example, a burst pipe. Floor electrodes are designed for use in dry rooms.

CPE-KNI with integrated galvanic separation:

• prevents the electrode circuits from interfering with each other
• prevents the formation of earth loops when more than one detector is connected to a common power supply circuit.

Capacitive plate sensors CPE -… must only be used in normally dry environments. They must be installed on the ground with the sensor side facing down and the label facing up.

Each capacitive panel sensor of type CPE -… is equipped with two round PCBs with gold-plated conductors with concentric strips. The rings as screening electrodes and the rings as measuring electrodes form 1 detection capacitor on the PCB. For symmetry reasons, there are two such capacitive sensing elements. As soon as a non-conductive liquid comes into contact with the rings and spaces of one or both of the capacitive sensing elements, the capacitance between the electrodes shall change and the switching state of the leak detector shall also change. If a conductive liquid is present, the rings of the capacitive sensing element are conductively bridged, which also results in a change in the switching state of the leak detector.

Capacitive measurement principle

The capacitive measuring principle is mainly used to detect electrically non-conductive (insulating) liquids, but can also be used to detect electrically conductive liquids.

Electrically non-conductive liquids are usually organic liquids, similar to oils and solvents. The electrode assembly is a capacitor and the dielectric is air or liquid. The dielectric constant of air is 1. The dielectric constant of the liquid to be detected is higher. For our capacitive sensors, the dielectric constant must be greater than 2 (CPE type) or 1.8 (OWE and COW type).

The capacitive leak detector recognises a change in the dielectric constant of the measuring capacitor and an alarm signal is triggered. The design of the measuring capacitor allows direct mounting on the ground and generally excludes the possibility of interference effects due to different substrates. The capacitive leak detector shall have an integrated electronic evaluation unit with galvanically isolated circuits. This prevents sensor circuits from interconnecting and forming earth loops if more than one of these leak detectors is connected and where the fluid detected is conductive.

CPE-KNI features

• design: leak detector with evaluation electronics as initiator for NAMUR circuit
• Detection capacitors: 2 circular PCBs with gold-plated concentric conduction band rings form 2 detection capacitors
• Housing: PP and cast resin
• electrical connection: two-wire connection via 2 x 0.75 connecting cable, 5 m long, longer connecting cable on request; halogen connecting cable on request
• supply voltage: only for connection to extra low voltage SELV or PELV! (see datasheet)
• output signal: impressed current signal in the power supply circuit
• operation: quiescent current principle
• switching state in case of cable break: I < 0.2 mA
• switching condition both sensing capacitors are activated: I ≤ 1 mA
• switching condition both sensing capacitors are not activated: I ≥ 3 mA
• switching status in case of short circuit or wrong polarity: I > 6 mA
• galvanic isolation: only for connection to extremely low voltage SELV or PELV! voltage resistance> 500 V between capacitor circuit, supply circuit and output circuit
• max. no-load voltage across the sensing capacitors: 5 Veff 200 kHz (safety extra-low voltage SELV)
• max. short-circuit current on sensing capacitors: 0.2 mA
• min. dielectric constant of the liquid to be detected: 2.0
• temperature range: – 20 °C to + 60 °C

For more technical information, please refer to the datasheet attached under the Documentation tab.

CPE-KNI use case: detecting fuel oil leaks