Coaxial probes solve this problem entirely. Powders and Other Materials Dry powders can be measured using similar methods to non-aqueous level methods, and similar issues apply. Also, moisture content may come into play since moisture can artificially raise the permittivity of the substance being measured and induce inaccuracies, by giving artificially elevated readings. If moisture content is variable, compensation methods may be required to correct the readings. These can take the form of conductivity probes or relative humidity meters.
Research is required to determine the form of correction measurement required.
In all cases there should be an air vent at the top of the coaxial probe to allow the fluid to rise in the probe column. Coaxial probes cost more but may make a difference between a successful design and a questionable one. A metal strip can be placed along the height of a vessel to look inside and measure the substance level within. If the tank is exposed to 'walk-by' traffic from human or mechanical motion nearby, the readings may be unreliable. The side strip should be shielded from such traffic by a grounded metal structure or screen around it.