Reliable continuous level measurement of a bulk solid in a silo can be attained by using guided wave radar sensors. Low level and high level alarm sensors are often but not limited to capacitance type probes.
Level measurement of slurry levels in a tank can be reliably attained with the use of ultrasonic level sensors. If your process slurry is susceptible to foaming due to water quality or additives or physical arrangement, special consideration should be taken.
For slurry level measurement differential pressure and high frequency radar sensor technologies are also used.