Robertshaw Model 728 Heavy Duty Level Probe
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 728 Heavy Duty Rigid Probe
The probe has a 15/32 O.D. stainless steel probe rod to give it extra strength for use in applications where side loading is a factor. The probe rod is available bare or Teflon insulated, which allows “tailoring” the probe for special applications.
They are available in lengths up to 20 feet. The vessel entrance gland is fitted with 1 inch NPT; standard material is 316 stainless steel. ANSI raised face flanges are optionally available in either carbon steel or 316 stainless steel and rated either Class 150 or Class 300.
These probes are available for use with any Robertshaw level control instrument, including the Level-Lance series, the Level-Tel and the Level-Tek units.
Typical applications of the Series 728B probes are in granular materials or highly viscous liquids that may be expected to exert significant bending forces on the probe rod.