Title of Invention

" FLUID INTERFACE LEVEL MEASUREMENT DEVICE"

Abstract

A fluid interface level measurement device comprising a free-floating float (F) means connected to a continous power source, said continuous power source being an external power source, said power source comprising an electrically insulated core (M), a first coil (C1) means external to the fluid and excitable by an external excitation means (U1), a second coil (C2) means comprising a search coil and connected to a control means provided on said float (F).

Full Text

FLUID INTERFACE LEVEL MEASUREMENT DEVICE Field of the invention The present invention relates to a fluid interface level measurement device. Background of the invention The manufacture of products/scientific experiments involves the storage of materials required to manufacture/experiment material during different stages of processing. In most processes, the materials required are stored in storage vessels. During manufacturing processes/scientific experiments, it is important to constantly monitor the levels of such materials in order to determine the quantities remaining and also their respective volumes, mass and hydrostatic pressures. Several physical principles are involved in the creation of solutions to the problem of level measurement during manufacturing/ scientific processes. The commonest solution to the problem of level measurement is to utilize sensors, which rely on air bubbles, differential pressure measurements, radiation, thermal, etc. to determine the levels of material in a storage vessel. US Patent 3,935,741 discloses A storage tank liquid level sensor for indicating levels of two immiscible liquids in the tank wherein a first magnet is carried by a float on top of one liquid and a second magnet is carried by a float on top of the other liquid, the first magnet operating a switch to indicate when the one liquid reaches a predetermined level and the second magnet moving a coded tape with respect to a read head in accordance with changes in the level of the other liquid, a transmitter to transmit data from the read head, a receiver for such data, an arithmetic logic unit to convert the data to binary coded decimals, a memory unit for storage of BCD data, and a display unit for selectively addressing the computer and displaying selected data. US Patent 6,408,692 discloses a liquid level sensor is provided that comprises an integral housing including therein a pickup tube, a return tube and a float cavity with a float positioned therein. Sensors are positioned within the float cavity for sensing the position of the float so as to determine the level of liquid within a tank or the like. US Patent 6401533 discloses a fluid level sensor that is particularly useful in fluid fuel tanks of motor vehicles wherein a resistor network is arranged on a fixed support and it is possible to generate an output signal from the resistor network which corresponds to the position of a float member. The level sensor has particularly low wear and is inexpensive to produce with a contact structure for the resistor network that operates through interaction of a magnetic member is moved by the float and can be deflected such that an electrical connection is dependent on the position of the float. However, prior art sensors suffer from several disadvantages. For example, the use of a specific sensor is limited to specific materials and cannot be applied across the board to different materials. Some prior art sensors such as slip tubes require manual operation thereby reducing the level of accuracy. In the case of vibrating switches, excessive material build up prevents operation of the sensor thereby rendering the sensor of no use in level measurement. Some prior art sensors, the principles employed therein and the disadvantages thereof are presented in Table 1 below (source: www.omega.com). As can be seen from Table 1, no one type of sensor has universal application across all industrial/scientific applications. It is therefore important to devise new sensors which overcome the disadvantages associated with the prior art sensors. Objects of the invention Accordingly it is an object of the invention to provide an interface level measurement device which overcomes the disadvantages of the prior art sensors enumerated above. Summary of the invention The present invention relies on the time tested method of float type level sensors. A body floating on the level of a liquid has been used since long in the field of instrumentation to measure the level of a liquid in a storage vessel. In the classic version of the float type level sensor, the movement of the float in the vertical direction depends on the level of liquid in the vessel and therefore provides a substantially accurate measurement of the liquid level in the vessel. A vertical guide prevents the movement of the float in the horizontal plane. The position of the float is ascertained using a position sensor such as a Linear Variable Differential Transformer (LVDT), magnets and the like. After the position is sensed, the signal is processed to generate a suitable signal, for example 4-20 mA for transmission. The upward/downward movement of the float is provided by buoyancy or more precisely gravity. This is a disadvantage in the use of such float type level sensors in a low gravity/microgravity environment such as in a space station. While float type sensors are useful where the fluids with a common interface comprise a gas and a liquid their applicability in storage vessels where the two interfacing fluids are both liquids is not very high. For example, where the two fluids having a common interface are both liquids with low differences in their respective densities, the buoyancy force acting on the liquid reduces significantly thereby affecting the movement of the float in the vertical plane. In such cases, small forces such as static friction, stickiness due to dirt and viscosity play a more significant role. Brief description of the accompanying drawings Figure 1 is a schematic of the interface level measurement device of the invention in actual operation in level measurement of a fluid level in a storage vessel. Figure 2 is a schematic of another embodiment of the interface level measurement device of the invention. Figure 3 is a schematic representation of the level measurement device of the invention. Figure 4 is another schematic representation of the level measurement device of the invention. Detailed description of the invention The present invention overcomes the problems of static friction and stickiness due to dirt. In it the float is continuously powered and provided with means to keep it free floating thus non-touching. This is achieved by the following means provided in the device of the invention: 1. Continuous power supply means for the float 2. Means to ensure the device is free-floating and non-touching with respect to the storage vessel, or any guide. 3. Sensor means provided to sense the position of float and connected therewith while being non-touching with respect to the vessel and external excitation coils 4. Float position signal transmitting means to transmit the position of the float to an external processing unit without wires and also maintaining non-touching state as mentioned in (2) above. 5. Interface position determination means provided within said float in order to provide correctional values to the float position, which may be needed due to density variation. The float is free floating. The set of position sensors and respective electromagnets are provided in the float in the same plane to each other. An online control means comprising a single board computer embedded in the float keeps the float centered around the core in cooperation with the position sensors and the electromagnets. The position of the float and therefore the interface level is sensed with a specially designed first excitation coil. The magnetic flux density of the first coil increases linearly from the bottom to the top. A first coil used in the device of the invention is provided external to the process fluid and is excited by an excitation means provided externally. Second coil which functions as a search coil moves freely inside the first coil. The signal generated by the second coil is linearly proportional to the position of the float. The search coil is connected to the control means provided in the float. The control means computes the position of the float and sends a coded signal through core to the external processing means. The external processing means processes the signal and converts it to a standard signal as per the requirement. Conventional float type level sensors which have a height to diameter ratio of greater than unity generate errors in the measured level due to the variations in the density ratio of the two fluids. The level of error is accentuated where the two fluids comprise liquids with marginal differences in densities. The design of the device of the invention permits level measurement where the height to diameter ratio of the float is less than unity. Figure 1 is a schematic of the interface level measurement device of the invention in actual operation in level measurement of a fluid level in a storage vessel. As explained above the float F is powered continuously from outside with magnetic induction through an electrically insulated core M. First coil means Cl is external to the fluid and is excited by an external excitation means Ul. The search coil C2 is connected to the control means provided in the float F. V is the vessel containing the fluids and the float F. PI and P2 are process connections for fluids. Figure 2 is a schematic of another embodiment of the level measurement device of the invention. The float is powered continuously from outside with magnetic "V induction either through an electrically insulated core M or through loosely coupled coils C4 and C5. The First coil means Cl is external to the fluid and is excited by an external excitation means Ul. The search coil is C2 is connected to the control means provided in the float F. C4 is external to the device and C5 is connected to the float. Figures 3 and 4 are schematic representations of the level measurement device (float F) of the invention. The electromagnet (EM) and position sensors (PS) are located at 90° to each other. F is the float. In figure 3, M is the core through which the float is continuously powered with magnetic induction. C3 is the coil of M. the control means comprises a single board computer (SBC). In both Figures 3 and 4, the electromagnetic means are represented by EM and the position sensors by PS. The device of the invention significantly reduces the level of electronics in the system thereby adding to the robustness of the device while enabling measurement of fluid levels where the densities of the interfacing fluids is marginally different. Problems due to viscosity, dirt and related stickiness, static friction and the like are avoided by making the float and sensor non-touching and intelligent. The schematics of the invention as contained in Figures 1 to 4 are embodiments of the invention. The disclosure contained herein is representative of embodiments of the invention and is not to be construed as limitative of the scope of the invention. Different types of Sensors available and their Limitations lwww.omega.com (Table Removed) We Claim: 1. A fluid interface level measurement device to measure the interface level in a process fluid contained in a vessel, said device comprising a free-floating float means connected to an external continuous power source means, a first coil means external to the fluid and excitable by an external excitation means, a second coil means comprising a search coil and connected to a control means provided on said float, position sensing means being provided operatively connected with said float means and said external excitation means to sense the position of the float means, said position sensing means being connected to float position signal transmitting means to transmit the position of the float to an external processing unit. 2. A device as claimed in claim 1, wherein, the float position sensing means comprises a plurality of float sensors and respectively connected electromagnets. 3. A device as claimed in claim 2, wherein, the plurality of position sensors and respective electromagnets are provided in the float in the same plane to each other. 4. A device as claimed in any of the preceding claims, wherein, the said power source comprises an electrically insulated core. 5. A device as claimed in any of claims 1 to 3, wherein, the said power source comprises a first and a second power induction coil, said power induction coils being external to the process fluid, and the second coil means being connected to control means provided on the float. 6. A device as claimed in any of the preceding claims, wherein, the float means is provided with an online control means comprising a single board computer embedded therein to keep the float means centered around the core in cooperation with the position sensors and the electromagnets. 7. A device as claimed in claim 1, wherein, the first coil means is provided external to the process fluid and is excitable by an external excitation means. 8. A device as claimed in claims 1 to 7, wherein the second coil means moves freely inside the first coil. 9. A device as claimed in claim 8, wherein, the second coil means is connected to the control means provided in the float means. 10. A device as claimed in any of the preceding claims, wherein, the control means comprises a single board computer. 11. A device as claimed in claim 1, wherein, the external power source comprises a magnetic induction power source. 12. A device as claimed in any of the preceding claims, wherein, the said position sensing means is provided, located at an angle of 90° to the external power source. 13. A device as claimed in claim 1, wherein, the magnetic core is provided with a third coil means.

Documents:

368-DEL-2002-Abstract-(05-12-2011).pdf

368-del-2002-abstract.pdf

368-DEL-2002-Claims-(05-12-2011).pdf

368-del-2002-claims.pdf

368-DEL-2002-Correspondence Others-(05-12-2011).pdf

368-del-2002-Correspondence-Others-(04-06-2013).pdf

368-del-2002-correspondence-others.pdf

368-del-2002-correspondence-po.pdf

368-del-2002-description (complete).pdf

368-DEL-2002-Drawings-(05-12-2011).pdf

368-del-2002-drawings.pdf

368-del-2002-form-1.pdf

368-del-2002-form-18.pdf

368-del-2002-form-2.pdf

368-del-2002-form-3.pdf

368-del-2002-form-4.pdf

368-del-2002-form-5.pdf

368-DEL-2002-GPA-(05-12-2011).pdf

368-del-2002-gpa.pdf