Robertshaw Capacitance Level Probes
These probes are used with Robertshaw RF and microprocessor based ON/OFF or continuous level controls for measuring applications involving liquids or granular materials.
When the probe is used with an ON/OFF (fixed level point) type, it may be installed in the vessel in either a vertical or horizontal position. If, however, the probe is to be used on a continuous level measuring application or on an application with a differential (such as Pump On/Pump Off), then it must be installed into the vessel in a vertical position.
Bent probes are available to allow the active length of the probe to be different from the installation direction. See "Bending Specifications."
When the process is a conductive liquid (such as water or sulfuric acid) and the vessel is non-metallic or non-metallic lined, a probe with a ground wire may be employed to provide a ground path to the liquid (second plate).
The liquid must be clean and free of foreign materials and be no more viscous than water.
The Robertshaw Level Measuring instruments have been designed so that they attach directly to the 1/2" NPT fitting on the top of the probe. Typically, these are either the complete transmitter housing or a conduit outlet box with a coaxial cable to the instrument. The 6-32 threaded fitting in the end of the probe rod accepts either a contact pin or a machine screw as required.
Model 732A "Short-Stop" probe
The Model 732A "Short-Stop" probe was designed for
those tricky and difficult applications where conductive
coatings or product buildups cause erroneous control action.
The "driven element" section of the probe along with the
advanced circuitry techniques of the instrument provide a
system that is completely reliable in those troublesome
applications. The Model 732A is recommended for ON/OFF
applications such as Latex paint, molasses, acids, moist
powder or granular products, etc.
The Model 732A can be used with the Model 5100 Level-Lance instrument. This unit has the necessary circuitry incorporated to utilize the capabilities of the Model 732A probe.
The Short-Stop probe is primarily designed for horizontal mounting at the desired trip point (control point). If vertical (top) mounting is required because of vessel geometry, the "trip" point can only be set at the tip of the probe. The instrument cannot be adjusted to obtain a trip point somewhere along the length of the probe.
This probe, the Model 732A, is designed for use in applications where the temperature does not exceed 350°F. For applications above that temperature limit, see the Robertshaw Model 727A High Temperature "Short-Stop" probe.