Capacitive Level Measurement Physics is Your Friend! Three Tips for Capacitive Level Measurement
The perfect man/machine relationship is the effective management of scarce resources. This presents a daily challenge for plant manufacturers and producers. In the area of raw material handling, UWT makes an important contribution.
Is Physics boring? If you do not take advantage of the knowledge and make good use of physics, then maybe. However, the opposite proves to be the case in the matter of capacitive measurement principles. The function of the capacitive switch is based on the change of the capacitive value depending on the type of filling material.
A capacitor is formed when a level sensing electrode is installed in a vessel: The metal rod of the electrode acts as one plate of the capacitor and the tank wall acts as the other plate. As the level of the solid rises, the air surrounding the electrode is displaced by material having a different dielectric constant. Consequently, the capacity between the two plates changes because the dielectric between the plates is now different.
The sensitivity of such a capacitive sensor circuit can vary greatly, depending on the dielectric constant (DK value), the sensor diameter, the material, approximate mass and the mounting position of the sensor. This can be adjusted by a potentiometer or dip switches.
Precise Level Measurement for Bulks
The major advantage of capacitive measurement is that it provides a precise and reliable method of point level detection regardless of the varying material properties that are found in applications across all industries. And crucially, the capacitive principle can be applied in a great variety of solids.
The new Capanivo (CN) 4000 from UWT is suitable for applications in bulk materials including high temperature or pressure applications and installations with material build-up such as in flour, grain, cement, pellets, coal or powder silos. The device is available with a housing of PA6 plastic or aluminium and suitable for temperatures from -40 °C and +180 °C. A weather protection cover protects the unit from environmental factors such as rain, condensation, excessive solar radiation and extreme cold in winter.
Read on why capacitive level measurement is both easy and adjustbale on page 2!
Flexibility for Level Measurement in Tanks and Silos
The device is available for supply voltages of 20-27 VDC, 21-230 VAC or 21-45 VDC and 20-40 VDC. Plus the CN4000 is suitable for all materials of a dielectric value of > 1.6. Through the Atex and IEC Ex approvals, it can be installed in dust and gas explosive environments. UWT has overcome the problem of the material build up and caking on the device often found in storage silos by the use of its active shield technology. Thus, material build up and caking are compensated for and the accurate level limit detection by the device is provided.
Capacitive Level Measurement – Simple and Durable
Other advantages of capacitive measurement systems are:
- An exposed/free standing earthed contact is integrated into the thread. This ensures that the grounding is installed automatically via the metal tank.
- The adjustable delay circuit prevents vibrating switching and allows a hysteresis (the lag in a variable property of a system) of the output signal.
- Multiple shaft lengths allow for complete customisation of the device according to the application’s requirements.
- Subsequent adjustments of the unit’s sensitivity are rarely required.
UWT devices are characterised by their simplicity and durability — features that also apply to the new CN 4000. UWT guarantees its products are uniquely maintenance free and corrosion resistant in a wide range of applications. ●