Level sensing

Following is a list of suppliers for level sensing technologies. 

Feedback is information in a closed-loop control system about the condition of a process variable. This variable is compared with a desired condition to produce the proper control action on the process. Information is continually "fed back" to the control circuit in response to control action. In the previous example, the actual storage tank water level, sensed by the level transmitter, is feedback to the level controller. This feedback is compared with a desired level to produce the required control action that will position the level control as needed to maintain the desired level. Figure 3 shows this relationship. 

Fig. 6.31. Level-sensing capacitor and associated bridge network (a) concentric cylinder capacitator (6) capacitance bridge...

Fig. 6.33. Various methods of level-sensing (a) vibrating-paddle level sensor (b) level measurement using magnetostriction (c) ultrasonic path...

Density of the fluid whose level is to be measured can have a large effect on level detection instrumentation. It primarily affects level sensing instruments which utilize a wet reference leg. In these instruments, it is possible for the reference leg temperature to be different from the temperature of the fluid whose level is to be measured. An example of this is the level detection instrumentation for a boiler steam drum. The water in the reference leg is at a lower temperature than the water in the steam drum. Therefore, it is more dense, and must be compensated for to ensure the indicated steam drum level is accurately indicated. 

Triangulation measurement is done at an angle, with a sharply focused laser beam directed toward an object. This method is suitable for only short-range measurements, primarily for the positioning of objects and robotics, not for level sensing. 

Small voltage generators (sensors) car crash sensors to activate air-bags, noise cancellation, active suspension for cars, anti- knock sensor for i.c. engines, liquid level sensing, etc. 

The tank was returned to service receiving a weak acid. The operators observed what appeared to be a rapidly rising liquid level. The level sensing device was actually reading the increasing pneumatic pressure as well as the slowly increasing liquid level as production was routed to the unvented vessel. Within a short time, the tank blew apart at the base. The tank fabricator estimated a failure of this nature could be reached as low as 2.5 psig (17 kPa). 

II Positive-level sense static D-type FF (latch). endmodule... 

II Positive-level sense, negative asynchronous clear, // positive asynchronous preset, static // D-type FF (latch). endmodule... 

Fig. 6.5-8 Schematic of a vertical pellet cooler [B.3, 1971] 1) feed hopper with level sensing device,...

Fig. 6.5-7 Components of a ring die pellet mill [B.3, 1971] 1) variable speed screw conveyor, 2) conditioner, 3) ring die and roller (extrusion) section, 4) speed reducer, 5) main motor, 6) machine base Fig. 6.5-8 Schematic of a vertical pellet cooler [B.3, 1971] 1) feed hopper with level sensing device, 2) cooling columns,...

The cause and effects diagram associated with the above SIF will show that on low low level sensed by LT-2, pump PI will stop and BSD valves XV-01 and XV-02 will close. 

In addition to desirable emulsions, a recurring feature in many process industries is the rag layer, a gel-like emulsion that forms and accumulates at the oil-water interface in the separation vessels of many industrial processes. Rag layers tend to concentrate a range of emulsion stabilizing components. Once formed, it can also trap additional components that would otherwise have creamed or settled out of the way. Rag layers can interfere with level-sensing monitors, short-out electrostatic grids, promote channeling flows, and, of course, prevent oil or water separation [87,88],... 

A level sensing device which signals to the control system. 

Institute for Energy and Environmental Research. 1992. Overview and Critique of the Current Approach to Radioactive Waste Management, Chapter 3, High-Level Dollars, Low-Level Sense, Takoma Park, MD. 

The level monitoring devices used for bulk loading systems are - deperuJing on the nature of the material handled - based on one of various operating principles mechanical, capacitive or inductive level sensing. 

Liquid level sensing devices are regularly tested to ensure proper operation. [ 112.6(a)(3)(iii)] ... 

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