Maintenance, Test & Measurement, Calibration


Hygienic limit switches for processes

February 2020 Maintenance, Test & Measurement, Calibration

Process and storage vessels incorporate limit switches to prevent overfilling of a tank or vessel (full indicator) or dry running of a pump (empty indicator). Anderson-Negele’s NCS series are ideally suited for the reliable measurement of limits in media with low water content, such as certain alcohols and cosmetics, providing universal application in bottling and pharmaceutical applications.

Capacitive working principle

Anderson-Negele level switches operate on the basis of the capacitive working principle. The measuring electrode, the medium and the conductive wall of the tank form an electrical capacitor influenced by three main factors: distance; area of the electrode surfaces; and type of medium between the electrodes.

The measuring electrode and the tank wall serve as the capacitor plates while the medium acts as the dielectric fluid. Due to the higher dielectric constant of the medium relative to air, the capacity increases when the electrode is immersed in the medium. Exposing the electrode has the opposite effect. The change in capacity is analysed by the level switch and converted to a corresponding switching command. The sensor outputs a 24 V DC signal (active output). The minimum and maximum (full/empty) switching functions can be swapped by reversing the polarity of the power supply. The capacitive working principle requires that the sensor tip, which is made of PEEK, be completely immersed in the medium. The advantage is that the sensor does not respond to foam or adherences and a signal is emitted only when the medium reaches the level. Capacitive measurement is most reliable when the dielectric conductivity and temperature of the medium are constant. Changes in the outer conditions are generally non-critical in media with high dielectric constant values.


Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Acoustic imager detects partial discharge
November 2020, Comtest , Maintenance, Test & Measurement, Calibration
Fluke’s new ii910 Precision Acoustic Imager detects corona, partial discharge and gas, steam and compressed air leaks that can hurt both production uptime and the bottom line.

Read more...
The Fluke T6 with FieldSense technology
October 2020, Comtest , Maintenance, Test & Measurement, Calibration
FieldSense technology works by providing a capacitive path from a contact point on the back of the tester and the operator’s hand to earth ground.

Read more...
Preventive maintenance in pulp and paper mills
October 2020, R&C Instrumentation , Maintenance, Test & Measurement, Calibration
The thinking around machine condition monitoring has changed over the years and it is now stated that vibration is the better measurement over temperature, since it gives earlier warning.

Read more...
Leak detection has never been quicker and easier
September 2020, SKF South Africa , Maintenance, Test & Measurement, Calibration
SKF’s TKSU 10 ultrasonic leak detector is able to identify leakages in compressed air and vacuum systems, delivering substantial savings for end-users by reducing inspection time and minimising energy costs.

Read more...
Best practices in measurement
September 2020, Yokogawa South Africa , Maintenance, Test & Measurement, Calibration
Operating envelopes are changing and the impact of these changes on instrumentation must not be underestimated. Instrumentation with a design rating of a particular capacity is heavily stressed when the load is increased.

Read more...
Internal inspection of machinery
September 2020, SKF South Africa , Maintenance, Test & Measurement, Calibration
The TKES 10 Endoscope Series from SKF is designed for fast, easy internal inspection of machinery, delivering significant savings in terms of both time and money to customers and end-users.

Read more...
Parker releases new software tool
September 2020, Parker Hannifin - Sales Company South Africa , Maintenance, Test & Measurement, Calibration
IQANgo enables service technicians or machine owners to connect wirelessly to modules in their machines, allowing them to perform a broad range of actions such as system status checks and troubleshooting errors or alarms.

Read more...
Condition monitoring solutions from Turck Banner
September 2020, Turck Banner , Maintenance, Test & Measurement, Calibration
Turck Banner’s retrofit solution can be used in industrial plants that do not yet fully support Industry 4.0 sensor-based condition monitoring. Machines can easily be monitored by customised systems, with data transmitted via wireless networks if required.

Read more...
Detect compressed air, steam, gas and vacuum leaks
September 2020, Comtest , Maintenance, Test & Measurement, Calibration
Comtest has introduced the Fluke ii900, a handheld sonic industrial imager that enables maintenance to quickly locate air, steam, gas and vacuum leaks in compressed air systems. The straightforward, intuitive ...

Read more...
Condition monitoring in the cloud
August 2020, Festo South Africa , Maintenance, Test & Measurement, Calibration
Detecting irregularities at an early stage and initiating the necessary measures before a system failure are now made possible by the dashboards and IoT gateway CPX-IOT from Festo. The turnkey, preconfigured ...

Read more...