Penberthy offers two models to meet your application needs: the Model 860 is a 4-wire, line powered transmitter, and the Model 862 is a 2-wire, loop-powered transmitter. In continuous level applications, as the process media rises or falls, the output is a proportional signal, usually 4 to 20mA. There are four basic types of applications:

Conductive Liquids and Slurries
Materials in this category include: water, acids, caustics, salt solutions, metal ore slurries, any water-based or ionic solution. An insulated probe must always be used in conductive media. Coating liquids in this category should be avoided.

Insulative Liquids and Slurries
Materials in this category include: oils, most solvents, essentially all hydrocarbons and non-polar liquids and slurries. In these applications, probe location is critical. The distance from the vessel wall to the probe should be kept at a minimum. If this isn't possible, a probe with a grounding sheath should be used.

Granulars
Materials in this category include: grains, crushed stones, any dry, solid product. These applications are similar to "Insulating Liquids and Slurries," however probe location is even more critical. The "angle of repose" must be considered to determine the optimal probe location. Also, moisture content is an important consideration. A change in moisture of only 2% to 3% is enough to make the product act like a conductive material. If you have granulars with particle sizes greater than 4mm, contact Penberthy. Lastly, probe strength must be considered because of the mass of the media involved.

Liquid-Liquid Interfaces
Essentially all level measurement is an interface -- Vapor - Air/Liquid - Granular. However, Liquid-Liquid Interfaces are special cases. Of the liquids involved, one must be conductive and the other insulative. There are two basic types of interfaces: Normal--the organic phase is above the aqueous phase. Inverted--the aqueous phase is above the organic phase. The depth of the emulsion layer (if any) needs to be considered. A large emulsion layer can result in a high error percentage.

Grounding Reference
The biggest factor affecting linearity is your ground reference. The distance between the probe and the tank wall is an important variable in determining capacitance. If this distance isn't constant a linear measurement becomes impossible. Typically, when measuring insulating liquids and slurries, or granulars, if a linear reference isn't available, use a probe with a concentric ground.