Product News

Plug & Play for filling levels

The NSK potentiometric level sensor from Negele is a reliable and tested technology for continuous level measurement that offers significant advantages, particularly in food industry applications.

22 Jul 2010

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The NSK potentiometric level switch from Negele is a reliable and tested technology that offers significant advantages, particularly in food industry applications:

  • Measurement is not affected by changes in media
  • Operation is reliable even in strongly adhesive media
  • Its rapid response time and high reproducibility make this method ideal for filling applications
  • Measurement is independent of conductivity and dielectric properties of the medium (Minimum required medium conductivity is only 1 µS/cm)
  • The device can be installed from top or bottom
  • Measurement is available over the entire rod length; no "inactive" areas as with guided radar
  • Simple startup without the need for calibration

In direct comparison to other measurement methods on the market today, such as float level sensors, capacitive sensors (admittance) or guided radar, the potentiometric method from Negele offers many advantages that are particularly relevant to the food industry, in which adhesive substances and changes in the media are common.

Magnetostrictive sensors with floaters are still in widespread use in the food industry today, but are difficult to clean and should therefore be viewed critically for hygienic reasons. In addition, the moving parts do not function reliably in pasty media or in materials with a solid content (such as fruit pieces).

While capacitive (admittance) sensors are in common use in many applications, primarily because of their comparatively low cost, this method is accompanied by certain limitations that are particularly disadvantageous in changing media. Because different media exhibit different dielectric properties, the device needs to be recalibrated to ensure reliable measurement every time the medium changes. This is a time-consuming process that is often performed when the container is being manually filled or emptied and results in additional costs.

A generally rugged and universally applied technique is the so-called TDR method (time-domain reflectrometry), or "guided" radar. For technical reasons, the rod used in guided radar has inactive regions at both ends where measurements are strongly non-linear and therefore very imprecise. The length of these inactive regions depends on the dielectric constant of the medium and sensor and can be several centimeters long. This is disadvantageous when using short rods and low containers.

In contrast, the potentiometric NSK measures along its entire rod length and achieves a measurement range of 100 mm to 3 m. In addition, the sensor can be installed from above or below, while radar sensors can only be installed from above. Yet another benefit is the lower purchase price compared to guided radar.

NSK Product Overview

Technical Article: "Rapid Response Time"