The can be used to measure the level of liquids and solids in a variety of tanks, bins, totes etc. These products are based on measuring the capacitance between a probe and the wall of the vessel. These are also classed as RF ( Radio Frequency) Admittance, RF Impedance level measuring devices. Robertshaw provide Control Units and Probes for Single Point, Multipoint ( two points on a single probe ) and Continuous ( 4-20ma current output). The continuous level measurement can be used with 4-20ma alarms to generate multiple alarms from a single probe. Units are avalable with general purpose enclosures and explosion proof enclosures for hazardous areas.
These units all require a capacitance probe to operate. See Probes
The Robertshaw Model 310 LEVEL-TEK is an all new RF capacitance sensing, on-off Control and Display
Instrument. Used primarily for detecting and controlling product
level changes in vessels or containers, it provides contact
closure for external control action by means of a DPDT plug-in
type, dust tight relay. The weather-tight unit has alarm
lights. This instrument is available with a choice of three supply
voltage variations, has adjustable differential (deadband) and adjustable time delay (response time). All adjustments
are multi-turn by means of sealed potentiometers.
Suitable for use on liquids and granular materials, the system will detect interface levels, flow-no-flow conditions, and operate under relatively high temperature and pressure conditions. It provides high accuracy, outstanding stability and excellent repeatability despite wide variations in ambient temperature or supply voltage.
The system utilizes a special triaxial cable (eliminates the effect of cable capacitance) as a means of electrically connecting a remotely mounted sensing probe to the control unit. The cable assembly consists of a conduit outlet box and special triaxial cable assembly designed for connection between the probe mounted into the vessel and the remotely mounted display/control unit containing the electronic circuitry.
This design allows easy access to all calibration adjustments when the system is used on elevated tanks or other inconvenient service areas. The conduit outlet box, mounted on the probe assembly, takes up only a small space on the tank.
The Control Unit assembly is available in a weather-tight enclosure with indicating lights for general purpose outdoor applications, or in an explosion-proof enclosure without lights for hazardous area applications.
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