APPARATUS FOR REMOTE MONITORING OF THE LEVEL OF LIQUID IN AT LEAST ONE TANK

Abstract: The present invention relates to a system for remotely monitoring the level of liquid medium in at least one tank. According to the invention, each tank is provided with a level sensor (1) connected to a control unit (3). The control unit includes a transceiver unit for communication with a central unit and is adapted to communicate with the central unit at specified times and to deliver an alarm signal should the level of liquid in the tank fall beneath a specified value. The system also enables the operating parameters of the control unit, such as its identity and the aforementioned specified times, to be installed from the central unit.

Description: APPARATUS FOR REMOTE MONITORING OF THE LEVEL OF LIQUID IN AT LEAST ONE TANK The present invention relates to apparatus for remote monitoring of the level of liquid medium in at least one tank. One problem with fuel-oil tanks for domestic dwellings for instance, which tanks must not be completely empty prior to being refilled, is that the consumption of oil is not constant in time, meaning that those oil tankers used to refill such tanks sometimes do not off-load all of their oil, whereas on other occasions they contain insufficient oil. It is known to solve this problem by providing tanks with alarm systems that deliver a signal to a central control unit when the oil in a consumer tank falls beneath a certain level. The knowledge imparted by the signals as to which tanks need to be refilled and the amount of oil involved in this respect enables the routes driven by the tankers and the amount of oil carried thereby to be planned more efficiently than was earlier the case. However, such systems do not continuously provide information relating to tank refilling requirements and optimisation of the routes followed by the tankers is not possible. An object of the present invention is to provide a level monitoring system which continuously delivers information relating to the level of liquid in the tanks monitored thereby, and which can be readily adapted to meet changed consumption conditions. This object is achieved in accordance with the invention by means of a system for remotely monitoring the level of liquid in at least one tank, said system being characterized in that each tank is provided with a level sensor which is connected to a control unit, in that the control unit includes a transceiver unit for communication with a central unit and is adapted to communicate with the central unit at specified times and to send an alarm signal when the level of liquid in the tank falls beneath a specified value, and in that the operating parameters of the control unit, such as said specified times, can be adjusted from the central unit. Such a system will continuously provide information relating to the level of liquid in tanks connected to the central unit, so that the person planning the refilling of the tanks will know exactly how much oil is required with each tank and therewith enable optimal use of tankers or the like. This continuous information will also give a clear indication of any change in consumption of the liquid content of a tank. This change may, for instance, require the level at which an alarm is given to be changed. A change in consumption can also influence other operating parameters, such as the interval between the times of communication with the central unit. Because the operating parameters can be controlled from the central unit, such changes can be easily carried out. In one preferred embodiment of the invention, the central unit and the control unit each include a telephone modem that is connected to the public telephone network. The control unit is designed to call the central unit at specified times and to recall the central unit when an attempt to call the unit fails. The control unit is also designed to calculate the volume of liquid medium remaining in the tank on the basis of the values measured by the level sensor and on the basis of the tank dimensions. The invention will now be described in more detail with reference to the accompanying Figure, which illustrates schematically one embodiment of a level sensor and a control unit suitable for use in the inventive system. The illustrated level sensor 1 is intended to be attached to the underside of a tank (not shown), e.g. glued thereto. The level sensor 1 is connected to a control unit 3 via a coaxial cable 2. The level sensor 1 includes a transmitter and a receiver of ultrasound pulses and the control unit 3 measures the time delay of the pulses reflected in the transition between liquid medium and gas/air in the tank. This time delay is proportional to the distance from the underside of the tank and the surface level of the liquid medium. The measuring principle used is well known to the person skilled in this art and need not be described in detail here. The central unit includes a computer unit, e.g. a personal computer, and a telephone modem connected to the public telephone network. The control unit 3 also includes a computer unit, for instance a microprocessor, and a telephone modem which can be connected to the public telephone network via an electric contact 4. The control unit can also be connected to the public electricity supply via a standard network transformer 5, preferably a so-called network adapter (plug with built-in transformer). The network transformer may, of course, be incorporated in the control unit and connected to the network through the medium of an electric contact or connected permanently by means of a cable. The control unit also includes a service contact 6 for connection to a series port on a personal computer, for instance. This input port enables a mounted control unit to be programmed on site or pre-programmed prior to being mounted. Mounting of the level sensor and a pre-programmed control unit is achieved very easily. The level sensor 1 is glued to a horizontal surface on the underside of the tank with the aid of an appropriate glue, for instance a superepoxy glue, so that the ultrasound pulses will be delivered generally vertically to the surface of the liquid medium in the tank. The control unit and the transformer are then affixed to a wall or like structure in some suitable manner, and the telephone modem is connected to the public telephone network and the transformer is connected to the public electricity supply network or mains. Mounting of these system components is now complete. Shortly after connecting the control unit to the electricity supply network, or mains, the control unit calls the central unit on a pre-programmed telephone number. This is indicated on the front of the control unit by a flashing light-emitting diode 7. When contact is established with the central unit, a further light-emitting diode 8 begins to flash. The control unit is programmed to recall the central unit after a given period of time has lapsed, when failing to contact the central unit. When contact with the central unit has been established, the control unit delivers its unique identity number that has earlier been allocated to the central unit. No further communication takes place between the control and central units until a preset time interval has lapsed. When contact with the central unit has been established, a third light-emitting diode 9 and the light-emitting diodes 7 and 8 begin to shine with a fixed light. After a given initiation time, the light-emitting diodes provide a rough indication of the level of liquid in the tank to which the level sensor 1 is affixed. The light-emitting diodes are controlled by the control unit so that the diode 9 will emit light when the tank is more than three-quarters full, the diode 8 will emit light when the tank is more than half full, and the diode 7 will emit light when the tank is less than one-quarter full. If the dimensions of the tank concerned are not programmed in the control unit, the control unit will operate on the basis of a parallelepipedic tank having a height of 3 m. As will be evident from the aforegoing, the control unit and level sensor are fitted in position very easily and can be mounted by untrained personnel, provided that a telephone jack and electric contact have earlier been installed. The fitter is able to leave the installation site, as soon as he/she has checked that the light-emitting diodes function in the aforedescribed manner. By pre-programmed is meant in the aforegoing that the control unit has been loaded with the program required for its operation and with data required for initiating operation, i.e. the relevant telephone number of the central unit, recall interval, and the time when the central unit shall next be called. If this pre-programming has not been implemented prior to fitting the aforesaid components, preprogramming can be implemented on site with the aid of a suitable computer, by connecting the computer to the service contact 4 and pre-programming the control unit via the computer . In conjunction with the first occasion of establishing contact with the central unit subsequent to fitting the aforesaid system components, the control unit is supplied with the dimensions of the tank and the type of tank concerned if this data was not available prior to preprogramming. The control unit calculates the volume of liquid medium remaining in the tank on the basis of this data and on the current measuring value of the level sensor 1, and sends this calculated value to the central unit. It may be appropriate to adjust the alarm level on this occasion, i.e. the liquid level at which the control unit shall call the central unit irrespective of when the alarm level is sensed, particularly when the tank dimensions were not known prior to fitting the aforesaid system components. In subsequent contacts with the central unit, the control unit thus sends to the central unit the current value of the volume of liquid medium remaining in the tank. In practice, a plurality of control units are connected to a plurality of tanks installed in different geographical locations and connected to the central unit via the telephone network. Because each control unit sends a status report to the central unit at regular intervals, the tank filling procedure can be optimised so as to achieve maximum use of tanker capacity, for instance. Furthermore, this regular monitoring of the tanks provides a clear indication of any change in the consumption of liquid medium in the tanks and provides a good time margin in planning the refilling of such tanks. A change in the consumption of the liquid medium in a tank may mean that the alarm level in respect of this tank should be changed. As mentioned earlier, the alarm level can be changed readily via the central unit in conjunction with the regular contact made between the central unit and the tank in question. Other operating parameters, such as time, the time interval between said regular contacts, the recall delay in the event of an unsuccessful attempt to contact the central unit, and so on, can also readily be changed via the central unit. If the dimensions of the tank to which the level sensor is connected are changed, for instance by connecting a further tank in series to the original tank or by replacing the original tank with a tank of different dimensions, the new tank dimensions can be readily entered into the control unit concerned via the central unit. New software can also be loaded into the control unit via the central unit. For instance, a volume calculating program for a new type of tank can be programmed in the control unit when the level sensor is connected to a tank that has a configuration that is different to those types of tanks that have already been taken into account in the pre-programming process . The described monitoring system is thus highly flexible and can be readily adapted to changes in both consumption patterns and tank types. Contact is preferably established between control units and central unit at times when traffic on the telephone network is low. Although the described system is primarily intended for use in conjunction with oil tanks or liquefied gas tanks, it may also be used, of course, with all liquid tanks where regular or on-going monitoring of a liquid level is required. By "tank" is meant all sizes of storage vessels for liquid or liquefied gas ranging from very large storage tanks and downwards . It will be understood that the described embodiment can be modified in several ways within the scope of the invention. For instance, other types of level sensors may be used, such as internally mounted level sensors, rows of photocells, etc., and the level sensor may be affixed to a tank by means other than glue. Other communications means than the telephone network may also be used, such as radio communication or data communications networks, and it is also conceivable to use mobile telephony technology when the tank concerned is placed far from the telephone line network. The invention is therefore restricted solely by the contents of the following Claims.

Claims: CLAIMS 1. A system for remotely monitoring the level of liquid medium in at least one tank, characterized in that each tank has fitted thereto a level sensor (1) which is connected to a control unit ( 3 ) , in that the control unit includes a transceiver unit for communication with a central unit and is adapted to communicate with the central unit at specified times and to send an alarm signal if the level of liquid medium in the tank falls beneath a specified value; and in that the operating parameters of the control unit, such as the aforesaid specified times, can be adjusted from the central unit. 2. A system according to Claim 1 , characterized in that the central unit and the control unit (3) each includes a computer unit and a telephone modem, said modems being connected to the public telephone network. 3. A system according to Claim 2, characterized in that the control unit (3) is constructed to call the central unit at specified times and to recall the central unit when a call attempt is unsuccessful. 4. A system according to any one of the preceding Claims, characterized in that the control unit (3) is adapted to calculate the volume of medium remaining in the tank on the basis of the measurement value of the level sensor (1) and on the basis of the tank dimensions.

Inventors: KNUTSSON LARS, KNUTSSON, LARS
Applicants: KNUTSSON LARS, LUTEC SYSTEMS AB, KNUTSSON, LARS
Application year: 1997
Main classification: G05D9
IPC codes: G01F23