Level Measurement & Control

Capacitive level switch for fluid, pasty and powdery media

May 2020 Level Measurement & Control

Martens, part of the GHM group of companies, has introduced its MLC 437 capacitive level switches for use principally for the registration of limit levels, full/empty signals in pipes and tanks in fluid, pasty and powdery media, and for the dry running protection of pumps.

Jan Grobler, managing director of GHM Messtechnik SA, commented: “The MLC 437 has an analog output and a DK-value (dielectric constant), which will open up the door for applications requiring the measurement of differences between oil and water levels – a crucial element to maintaining consistency in the manufacture of products such as chemicals, pharmaceuticals and cosmetics, including applications where hygienic areas are essential”.

The design of the switch makes it suitable for hygienic applications in the hygienic and the chemical industry. The parts of the Martens MLC437 switch that come into contact with the media, consist only of materials which conform to FDA. With the aid of the microprocessor-controlled measurement, the user can adapt the parameter setting to the process environment using a PC.

“A unique feature of the MLC437 is that during operation, if an error or condition occurs, the display backlight can be set to change colour,” said Grobler. “This is an easily identifiable alert for engineers to see the condition and address the error.”

During measuring operations, the LCDisplay shows measured values. According to parameterisation, the backlight can be permanently operational or the device can enter the power safe mode.

The Marten MLC437 capacitive level switches register fluid, granular and pulverised media (not for use in areas subject to the risk of explosion). This charge transfer measurement procedure makes use of the storage capability of charges in the medium. The switch tip and the tank wall (or built-in adaptor/sleeve) thereby form an electrical condenser.

If the switch is in the air, a specific low initial capacity is measured. When the switch is immersed in the medium, the capacity change is based on a change in the effective permittivity in the area of the measuring tip. This value is determined by the geometry of the switch and the DK-value of the medium. The measurement procedure enables the monitoring of the product and the detection of any separating layer, e.g. water/oil. Influences due to foam formation and adhesions are minor to non-existent.

Technical features

Power supply – supply voltage: 18-30 V DC, (100 mA max); electrical connection: M12x1 plug; CE conformity: EN 61326:2007-05; ambient temperature: -20°C to 60°C; climatic class: EN 60068-2-38:2010-06; vibration class: EN 60068-2-6, GL test2; certifications: EHEDG Certificate No. 28/2011.

Sensor – radiated frequency 40,68 MHz, <1 mW; measuring range: DK-value 1,5 – 175; initialisation time: 3 seconds; process temperature: -20°C to 100°C; CIP-/SIP-capable; process pressure: -1 to 10 bar; process material: PEEK, FDA approval number 21CFR177.2415 (food-safe according to EHEDG and conforms to Regulation EC 1935/2004 and 10/2011).

The switches are easy to service and maintain.


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