OWE-LS4/A JOLA hanging electrode

Description

The OWE-LS4/A JOLA hanging 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.

OWE-LS4/A 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 suspension sensors OWE -… must only be used in normally dry environments.

They must be installed with the sensor facing downwards. Three gold-plated PCBs are integrated in a capacitive suspension sensor of type OWE -….. The two outer single-sided gold-plated PCBs as screening electrodes and the double-sided gold-plated inner PCB as measuring electrode form a double capacitor. As soon as a non-conductive liquid flows into the space between the PCBs, the capacitance between the PCBs changes, as well as the switching state of the leak detector. If a conductive liquid is present, the boards are conductively bridged, which also causes 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.

Features of the OWE-LS4/A

• design: leak detector with relay output
• sensing capacitors: 2 external single-sided gold-plated PCBs and 1 internal double-sided gold-plated PCB form a double capacitor
• Housing: PP and cast resin
• electrical connection: four-wire connection via 4 x 0.5 connecting cable, 5 m long; equipped with halogen connecting cable on request
• supply voltage: only for connection to extra low voltage SELV or PELV! (see datasheet)
• Energy consumption: approx. 0.5 VA
• output: potential-free contact of operating current (NO), max. load AC/DC 5 … 24 V (very low voltage SELV or PELV only); AC/DC 1 mA … 3 (1) A; wire colours: black and dark grey
• switching condition without supply voltage: output relay energised, output contact closed
• switching capacitor for state detection not activated: output relay de-energised, output contact open
• switching capacitor for state detection is activated: output relay energised, output contact closed
• 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 40 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: 1.8
• temperature range: – 20 °C to + 60 °C

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

Application example OWE-LS4/A: fuel oil leak detection