Petrochemical Process Control Design Manual, 4th Edition – Guided Wave Radar Interface Measurement
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As shown in the figure, I’m not quite sure about point 5 – should the lower limit of the dielectric constant for the upper layer be greater than 3? Is the lower limit of the dielectric constant greater than 20?
The dielectric constant is high, resulting in a strong returning signal; therefore, the value below must be greater than that above
So you actually don’t know anything; how can one measure a dielectric constant that is not greater than 3? That’s a non-conductive liquid, such as liquefied gas. The value of 20 or more is required to meet the second requirement – the dielectric constants of both liquids must be greater than 10.
We are in the field of instrument application, not design and research; this is the scope of use, so there’s no need to be too literal