Why RF Admittance Level Switch Cannot Measure Ore or Slag

The development is rapid in the modern industrial measurement instrumentation industry, and the failure rate is also reduced, but still, any instrumentation will have the probability of failure.

RF Admittance Level Switches, or Radio Frequency Admittance Level Transmitters, are not versatile instruments. In a Cape-11 RF Admittance Level Switch, a probe is designed to detect the change of capacitance and impedance between probe and vessel wall to realize level measurement and control. In its electronic unit, reactance between the measurement electrode and the wall of an empty vessel constitutes a balanced bridge circuit which outputs a stable oscillation signal. As the level rises, the measurement electrode is covered by the medium, and reactance between the electrode and the wall of the vessel changes. It causes an imbalance of the bridge circuit and stops the oscillation as a result. A post-circuit is designed to detect the change of output signal from the bridge circuit and generate an alarm signal.

In practical applications, RF Admittance Level Switches are mainly used for measuring coal ashes. So, why cannot RF Admittance Level Switches be used to measure ore or slag?

The RF Admittance Level Switch requires the measured medium to have stable dielectric constant in order to achieve accurate measurement.

When measuring ore or slag, the uneven particle size, the humidity alternation, and other factors such as dust flying, may lead to unstable dielectric constant. The uneven particle size can also result in incomplete contact between the probe and the medium. Meanwhile, the lumpy solids have strong impaction on the instrumentation probe during the material filling, causing abrasive wear and damage to the probe.

Therefore, when selecting the RF Admittance Level Switch, the on-site environment should be considered. Generally speaking, the specific factors also mainly include the process connection, density, temperature, pressure, insertion length and so on.

According to different demands towards different circumstances, Jiwei provides a variety of level meters for users to choose from, such as Tube-11 Vibrating Rod Level Switch (double vibration elements), Fork-11 Tuning Fork Level Switch, Spin-11 Rotary Paddle Switch and Cape-11 RF Admittance Level Switch.