Robertshaw Capacitance 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 729A Flexible Probe
The Model 729A Flexible Probe is a general purpose probe designed to cover most applications where
non-rigid probes are required or desired. Typical applications of the flexible probe are in large tanks where rigid probes are prohibitive or where overhead room precludes the use of
The standard conductor on the Model 729A is made of 316 stainless steel multi-strand cable that is offered as:
(a) A bare cable for use in dry products,
(b) Teflon insulated cable,
(c) Polyethylene insulated cable.
Any of these are available with or without a lower end termination fitting. This termination fitting is constructed of stainless steel or of non-metallic material that is the same as the insulating
material on the cable. The stainless steel termination fitting should only be used in dry or granular products or in non-conductive low dielectric liquid products whereas the non-metallic termination fitting is to be used only in liquid products, either conductive or non-conductive.
The Model 729A Flexible Probe can be "tailored" to meet nearly any specific application
by the addition of options that are readily available. These options include:
• Weights and turnbuckle for holding the probe down.
• An "eye" (termination) for tying the probe down to the bottom of the vessel when required (liquid products only).
• Flanges either welded or screwed onto the probe gland.