Abstract:
The present disclosure relates to a dispenser for dispensing a liquid (LQ). The dispenser has a housing for receiving a removable container containing the liquid (LQ). Dispensing means are provided for dispensing the liquid (LQ) from the container. The dispenser includes a capacitive sensor having a sensing element for positioning proximal to an exterior of the container. A processor is provided for receiving a capacitance signal (SIG 1 ) from the capacitive sensor. The processor is configured to estimate a quantity of liquid (LQ) in the container in dependence on said capacitance signal (SIG 1 ). The present disclosure also relates to a method of estimating a quantity of liquid (LQ) in a container.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of GB Patent Application No. 1520277.3 filed Nov. 17, 2015, entitled “DISPENSING APPARATUS AND METHOD” which is hereby incorporated herein by reference in its entirety, including all references cited therein. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO A SEQUENCE LISTING 
       [0003]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present disclosure relates to a dispensing apparatus and method. More particularly, the present disclosure relates to a dispenser having a sensor for estimating a quantity of liquid in a container; and a method of estimating a quantity of liquid in a container. The present disclosure also relates to an apparatus for estimating a quantity of liquid in a container. 
         [0006]    2. Background Art 
         [0007]    It is well known to provide a dispenser in a public washroom to dispense soap. The soap is typically stored as a liquid in a container within the dispenser. The container is removably mounted in the dispenser. The washroom is periodically inspected and the dispenser serviced by replacing the container. The quantity of liquid remaining in the container may be estimated indirectly by counting the number of times that the dispenser is actuated. However, this approach relies on an assumption that the dispenser dispenses a uniform amount of the liquid each time it is actuated. In practice, the amount of liquid remaining in the container may differ significantly from the estimation. It would be desirable to measure the amount of liquid directly to provide a more accurate indication of servicing requirements. 
         [0008]    It is against this backdrop that the present invention has been conceived. At least in certain embodiments, the present invention seeks to provide a dispenser which overcomes or ameliorates some of the shortcomings associated with the prior art. 
       SUMMARY OF THE INVENTION 
       [0009]    Aspects of the present invention relate to a dispenser; to an apparatus for estimating a quantity of liquid in a container; and to a method of estimating a quantity of liquid in a container. 
         [0010]    According to a further aspect of the present invention there is provided a dispenser comprising: (a) a housing for receiving a removable container containing a liquid; (b) dispensing means for dispensing the liquid from the container; (c) a capacitive sensor comprising a sensing element for positioning proximal to an exterior of the container; and (d) a processor for receiving a capacitance signal from the capacitive sensor, the processor being configured to estimate a quantity of liquid in the container in dependence on said capacitance signal. The capacitance signal provides an indication of the capacitance between the sensing element and the liquid contained in the container. A capacitive coupling may be established between the sensing element and the liquid in the container. Changes in the quantity of liquid in the container change the capacitance signal generated by the capacitive sensor. The processor thereby determines the quantity of liquid in the container. The capacitance signal may be generated in dependence on a measured electrical current in the sensing element. The sensing element may be separated from the liquid by a nonconductive (dielectric) layer, for example a wall of the container. The liquid may be electrically conductive. 
         [0011]    The capacitive sensor may be provided in the housing and form a component part of the dispenser. At least in certain embodiments, it is not necessary to provide a sensor in the container, allowing the dispenser to be used in conjunction with a conventional container. 
         [0012]    The processor may be configured to estimate the quantity of liquid in the container in proportion to the received capacitance signal. The processor may be configured to estimate the quantity of liquid in the container in proportion to the received capacitance signal above a lower signal threshold and/or below an upper signal threshold. An operating range of the capacitive sensor may be defined by a lower signal threshold and/or below an upper signal threshold. At least within said operating range, the quantity of liquid in the container is directly proportional to the received capacitance signal. The processor may be configured to provide an estimate of the quantity of liquid in the container in direct proportion to the received capacitance signal at least within said operating range. The estimate may comprise continuous data (i.e., the estimate may be any numerical value within a range) or may comprise discrete data (i.e., the estimate may be a plurality of discrete numerical values within a range). The processor may define a mathematical function to relate the received capacitance signal to the quantity of liquid in the container. The mathematical function may comprise a linear function or a polynomial function operative to relate the received capacitance signal to the quantity of liquid in the container. The mathematical function may be defined within said operating range of the capacitive sensor. 
         [0013]    The lower signal threshold may correspond to a predetermined quantity of liquid in the container. The lower signal threshold may represent a background or base signal when the container is empty. The lower signal threshold may be predefined. The upper signal threshold may correspond to a predetermined quantity of liquid in the container. The upper signal threshold may represent a full container. Alternatively, the upper signal threshold may represent a maximum measurable quantity of liquid in the container. The upper signal threshold may be predefined. 
         [0014]    A plurality of capacitance bands may be predefined. The capacitance bands may be defined by a plurality of capacitance thresholds. Each capacitance band may correspond to a predetermined quantity of liquid in the container. The capacitance bands may be stored in a look-up table accessed by the processor. The processor may be configured to identify one of said predefined capacitance bands in dependence on the received capacitance signal. The identified capacitance band may be used to estimate the quantity of liquid in the container. The processor may determine when the quantity of liquid in the container is substantially equal to one of the predetermined quantities of liquid by determining when the received capacitance signal is substantially equal to or falls within one of the plurality of predefined capacitance bands. 
         [0015]    The look-up table may be stored in a storage device coupled to the processor. The look-up table may, for example, be stored in system memory disposed in the dispenser. Alternatively, the look-up table may be stored remotely, for example in a base station, and accessed over a communication network. 
         [0016]    The sensing element may be adapted to be positioned proximate to a lower portion of the container. The sensing element may be adapted to be positioned proximate to a bottom wall of the container. The sensing element may be adapted to be positioned proximate to an underside of the bottom wall. The capacitive sensor may contact the underside of the bottom wall of the container. 
         [0017]    The sensing element may be adapted to contact an exterior of the container. The sensing element may be adapted to contact the container when the container is installed in the housing. The sensing element may be spring biased against the exterior of the container. The sensing element may be adapted to be positioned against an underside of a base of the container. The sensing element may comprise a resilient element to provide said spring bias. 
         [0018]    The processor may be configured to output an estimated quantity signal. The estimated quantity signal may comprise an estimated volume of the liquid in the container. Alternatively, or in addition, the estimated quantity signal may comprise a ratio or a percentage expressing the estimated quantity of liquid in the container as a proportion of the liquid held in the container when full. The processor may be coupled to a transmitter for transmitting the estimated quantity signal. The estimated quantity signal may be transmitted to a base station. The transmitter may, for example, be a radio frequency (RF) transmitter. 
         [0019]    A support member may be provided for supporting the container. The support member may be fixedly mounted in the housing to provide a fixed platform for supporting the container. The container may be at least partially supported by said support member. The dispenser may be configured such that, in use, the position of the container in in the housing is fixed. The sensing element may be associated with said support member for positioning proximal to the container. The sensing element could be incorporated into said support member, for example moulded into the support member. Alternatively, the sensing element may be disposed in an aperture or recess formed in the support member, for example in an upper surface of the support member. Alternatively, the sensing element may be disposed above the support member. For example, the sensing element may be disposed above an upper surface of the support member. When the container is installed, the sensing element may be configured to locate between said support member and the container. 
         [0020]    The dispenser described herein may be configured for dispensing a washing agent, such as a soap, from the container. The soap may be stored in the container in a liquid form. 
         [0021]    According to a further aspect of the present invention there is provided a dispenser comprising: (a) a housing for receiving a removable container containing a liquid; (b) dispensing means for dispensing the liquid from the container; (c) a capacitive sensor comprising a sensing element for positioning proximal to an exterior of the container; and (d) a transmitter for transmitting a capacitance signal generated by the capacitive sensor to a remote processor. The sensing element may be disposed proximal to a base of the container, for example proximal to an underside of a bottom wall of the container. The sensing element may contact the underside of the bottom wall of the container. 
         [0022]    The transmitter may be a wired transmitter or a wireless transmitter, for example a radio frequency (RF) transmitter. The capacitance signal may be transmitted over a communications network, such as a local area network (LAN), a wide area network (WAN) or the internet, to be processed remotely. The processor may, for example, be provided in a base station. The base station may, for example, comprise one or more server. The base station may be coupled to a plurality of said processors and configured to schedule servicing or maintenance in dependence on the estimated quantities of liquid. 
         [0023]    According to a further aspect of the present invention there is provided an apparatus for estimating a quantity of liquid in a container, the apparatus comprising: (a) a capacitive sensor comprising a sensing element for positioning proximal to an exterior of the container; and (b) a processor for receiving a capacitance signal from the capacitive sensor, the processor being configured to estimate a quantity of liquid in the container in dependence on said capacitance signal. The processor may be configured to estimate the quantity of liquid in the container in proportion to the received capacitance signal. 
         [0024]    A plurality of capacitance bands may be predefined, each capacitance band corresponding to a predetermined quantity of liquid in the container. The processor may be configured to identify one of said predefined capacitance bands in dependence on the received capacitance signal. 
         [0025]    The sensing element may be adapted to be positioned proximate to a lower portion of the container. The sensing element may be adapted to be positioned proximate to a bottom wall of the container. The sensing element may be adapted to be positioned proximate to an underside of the bottom wall. The sensing element may contact the underside of the bottom wall of the container. 
         [0026]    According to a still further aspect of the present invention there is provided a dispenser comprising apparatus as described herein. 
         [0027]    According to a yet further aspect of the present invention there is provided a method of estimating a quantity of liquid in a container, the method comprising: using a capacitive sensor to generate a capacitance signal and estimating a quantity of liquid in the container in dependence on said capacitance signal, wherein the quantity of liquid in the container is estimated in proportion to the received capacitance signal. The capacitance signal provides an indication of the capacitance between the sensing element and the liquid contained in the container. A capacitive coupling may be established between the sensing element and the liquid in the container. Changes in the quantity of liquid in the container change the capacitance signal generated by the capacitive sensor. The capacitance signal may be generated in dependence on a measured electrical current in the capacitive sensor. The quantity of liquid in the container may be directly proportional to the received capacitance signal. 
         [0028]    The quantity of liquid in the container may be estimated with reference to a plurality of predefined capacitance bands, each capacitance band corresponding to a predetermined quantity of liquid in the container. The method may comprise identifying one of said predefined capacitance bands in dependence on the received capacitance signal. 
         [0029]    The sensing element may be disposed proximal to an exterior of the container. In certain embodiments, the sensing element may be disposed proximal to a base of the container. The container may be provided in a dispenser in which the capacitive sensor is installed. 
         [0030]    The method may comprise estimating the quantity of liquid in the container in direct proportion to the received capacitance signal at least within said operating range. The estimate may comprise continuous data (i.e., the estimate may be any numerical value within a range) or may comprise discrete data (i.e., the estimate may be a plurality of discrete numerical values within a range). The method may comprise applying a mathematical function which relates the received capacitance signal to the quantity of liquid in the container. The mathematical function may comprise a linear function or a polynomial function. The application of the mathematical function may enable the quantity of liquid in the container to be estimated in dependence on the received capacitance signal. The mathematical function may be defined within an operating range of the capacitive sensor. 
         [0031]    A processor may be provided to estimate the quantity of liquid in the container. The processor may be provided locally, for example in the dispenser. Alternatively, the processor may be provided remotely. The capacitance signal may be transmitted over a communications network, such as a local area network (LAN), a wide area network (WAN) or the internet, to be processed remotely. The processor may, for example, be provided in a base station. The base station may, for example, comprise one or more server. The base station may be coupled to a plurality of said processors and configured to schedule servicing or maintenance in dependence on the estimated quantities of liquid. 
         [0032]    It will be understood that the term liquid used herein also covers gels and creams. 
         [0033]    The processor may be configured to execute a set of computational instructions stored in a non-transitory computer-readable media. The computational instructions may be read from said non-transitory computer-readable media into system memory for execution by the processor. 
         [0034]    Any control unit described herein may suitably comprise a computational device having one or more electronic processors. The system may comprise a single control unit or alternatively different functions of the control unit may be embodied in, or hosted in, different control units. As used herein the term “control unit” will be understood to include both a single control unit and a plurality of control units collectively operating to provide any stated control functionality. To configure a control unit, a suitable set of instructions may be provided which, when executed, cause said control unit or computational device to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more electronic processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said control unit to be executed on said computational device. The control unit may be implemented in software run on one or more processors. One or more other control unit may be implemented in software run on one or more processors, optionally the same one or more processors as the first control unit. Other suitable arrangements may also be used. 
         [0035]    As used herein the term “processor” will be understood to include both a single processor and a plurality of processors collectively operating to provide any stated control functionality. To configure a processor, a suitable set of instructions may be provided which, when executed, cause said processor to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said processor to be executed on said processor. The instructions may be provided on a non-transitory computer readable media. 
         [0036]    Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]    One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which: 
           [0038]      FIG. 1  shows a perspective view of a dispenser in accordance with an embodiment of the present invention; 
           [0039]      FIG. 2  shows a sectional view through the dispenser shown in  FIG. 1 ; 
           [0040]      FIG. 3  shows a perspective view of the dispenser with the container removed; 
           [0041]      FIG. 4  shows an enlarged perspective view of a sensing element of the capacitive sensor; 
           [0042]      FIG. 5A  shows a front elevation of the dispenser with the cover omitted; 
           [0043]      FIG. 5B  shows a side elevation of the dispenser with the cover omitted; 
           [0044]      FIG. 6  shows a schematic representation of the electronic control unit and capacitive sensor in accordance with an aspect of the present invention; 
           [0045]      FIG. 7  shows a perspective view of a dispenser in accordance with a further embodiment of the present invention with the cover in an open position; and 
           [0046]      FIG. 8  shows an enlarged perspective view of a sensing element of the capacitive sensor in the embodiment shown in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    A dispenser  1  for dispensing a liquid LQ in accordance with an embodiment of the present invention will now be described with reference to the accompanying figures. In the present embodiment the dispenser  1  is suitable for use in a washroom and the liquid LQ to be dispensed is a liquid soap. 
         [0048]    A perspective view of the dispenser  1  with a container  2  containing the liquid LQ is shown in  FIG. 1 . The container  2  can be removed from the dispenser  1  and replaced when the liquid LQ is depleted. The container  2  is of conventional design and comprises a one-piece body moulded from a plastics material. In the present embodiment the container  2  has an internal volume of approximately 650 ml for containing the liquid LQ. As shown in  FIG. 2 , the container  2  comprises a bottom wall  3 , a sidewall  4  and a top wall  5 . The bottom wall  3  is disposed at the bottom of the container  2  and extends substantially horizontally. The sidewall  4  in the present embodiment is deformable, but alternate embodiments may incorporate a rigid sidewall. A valve assembly  6  is mounted to the bottom wall  3  and is adapted to dispense a metered volume of the liquid LQ when the dispenser  1  is operated. In the present embodiment the bottom wall  3  has a concave profile and the valve assembly  6  is mounted at the lowermost extent of the bottom wall  3  to promote the flow of the liquid LQ into the valve assembly  6 . The valve assembly  6  comprises an upper valve  7  and a lower valve  8  disposed at opposing ends of a deformable pumping chamber  9 . A dispensing nozzle  10  is provided at the bottom of the valve assembly  6 . The upper and lower valves  7 ,  8  are one-way valves arranged in series to allow the liquid LQ to be dispensed from the container  2 . The upper valve  7  inhibits the return of the liquid LQ from the tubular member  11  into the container  2 . The pumping chamber  9  in the present embodiment is formed by a resilient tubular member  11 . In use, an actuating force is applied to deform the tubular member  11 , thereby reducing its internal volume and expelling liquid LQ through the lower valve  8 . When the actuating force is removed, the tubular member  11  returns to its un-deformed state and liquid LQ is drawn into the pumping chamber  9  through the upper valve  7 . 
         [0049]    With reference to  FIGS. 1 and 2 , the dispenser  1  comprises a housing  12 , a dispensing actuator  13 , a capacitive sensor  14 , an electronic control unit  15  and a transmitter  16 . The housing  12  comprises a mounting plate  17 , a support frame  18  and a pivotally mounted cover  19 . The mounting plate  17  is adapted to be mounted to a wall to mount the dispenser  1 . The support frame  18  projects outwardly from the mounting plate  17  and is adapted to support the container  2 . As shown in  FIG. 3 , the support frame  18  comprises a cup-shaped member  20  for receiving the bottom wall  3  of the container  2 . The cup-shaped member  20  has a base panel  21  which extends substantially horizontally. A support member  22  is disposed at the front of the cup-shaped member  20  for locating the container  2  within the housing  12 . The support member  22  is profiled to match the profile of the underside of the bottom wall  3 . The support member  22  also locates the capacitive sensor  14  against the underside of bottom wall  3 . The valve assembly  6  extends through an aperture  23  formed in the base panel  21 . The cover  19  is pivotally mounted to a lower portion of the mounting plate  17  and, in use, is movable between an open position (as shown in  FIG. 1 ) and a closed position (not shown). The cover  19  is pivoted to said open position for servicing, for example to replace the container  2 ; and pivoted to said closed position for use. 
         [0050]    As shown in  FIGS. 2 and 3 , the dispensing actuator  13  comprises a lever  24  pivotally mounted to the support frame  18 . The lever  24  comprises an actuating arm  25  (shown in  FIG. 2 ) arranged to cooperate with the valve assembly  6  to dispense the liquid LQ. When the lever  24  is actuated, the actuating arm  25  applies an actuating force to the tubular member  11 . The tubular member  11  is deformed and the liquid LQ is dispensed through the lower valve  8 . A return spring (not shown) is provided to return the lever  24  to a standby position, as shown in  FIG. 1 . The dispensing actuator  13  provides dispensing means for dispensing the liquid LQ from the container  2 . The dispensing actuator  13  in the present embodiment is a manually operated mechanism, but in alternative embodiments the dispensing actuator  13  could be automated, for example by an electric drive motor or a solenoid. 
         [0051]    The capacitive sensor  14  comprises a sensing element  26  and a sensor control unit  27 . The sensing element  26  is adapted to be positioned proximal to the bottom wall  3  of the container  2 . In the present embodiment, the sensing element  26  is configured to locate against an underside of the bottom wall  3 . The sensing element  26  is formed from an electrically conductive material. As shown in  FIG. 4 , the sensing element  26  comprises a length of metal wire formed into a U-shaped loop. The sensing element  26  is inclined upwardly so as to engage the bottom wall  3  when the container  2  is installed in the housing  12 . The sensing element  26  is a resilient member which is spring-biased against the underside of the bottom wall  3  to establish a physical contact with the container  2 . The sensing element  26  is deflected when the container  2  is installed and held in position between the underside of the bottom wall  3  and the support member  22 . The sensing element  26  extends towards the lowermost portion of the container  2  where the valve assembly  6  is mounted to the bottom wall  3 . This arrangement helps to ensure that the positioning of the sensing element  26  and the container  2  relative to each other remains at least substantially unchanged each time the container  2  is replaced. As illustrated in  FIG. 6 , the sensor control unit  27  comprises a first processor  28 . The first processor  28  comprises an operational amplifier and an analogue-to-digital (ADC) converter. 
         [0052]    The liquid LQ is electrically conductive and forms a target object for the capacitive sensor  14 . The bottom wall  3  of the container  2  is formed from a nonconductive (dielectric) material which forms a gap between the capacitive sensor  14  and the liquid LQ. The distance between the capacitive sensor  14  and the liquid LQ in the bottom of the container  2  is constant. However, changes in the quantity of the liquid LQ in the container  2  alter the effective size of the target object which results in a change in capacitance between the capacitive sensor  14  and the liquid LQ. As described herein, the capacitive sensor  14  is configured to detect changes in the capacitance and, thereby, to estimate the quantity of liquid LQ in the container  2 . The inventor(s) in the present case have determined that in certain embodiments the changes in the capacitance are at least partially dependent on a level L of the liquid LQ in the container  2 . Thus, measuring the capacitance between the capacitive sensor  14  and the liquid LQ may provide an indication of the level L of the liquid LQ in the container  2 . The level L of the liquid LQ in the container  2  is illustrated in the front and side elevations of the dispenser  1  shown in  FIGS. 5A and 5B . 
         [0053]    In use, an alternating voltage is supplied to the sensing element  26  to establish an electrical field. The electrical current in the sensing element  26  varies in dependence on the capacitance between the capacitive sensor  14  and the liquid LQ. The electrical current in the sensing element  26  can be measured to provide an indication of the capacitance. The electrical current measured by the sensing element  26  is supplied to the operational amplifier of the first processor  28 . The amplified signal is converted by the analogue-to-digital converter to a digital signal, for example comprising a binary or hexadecimal value. The digital signal represents a capacitance signal SIG 1  which is output by the first processor  28 . The capacitance signal SIG 1  is output from the capacitive sensor  14  to the electronic control unit  15 . The capacitance signal SIG 1  is generated in dependence on the electrical current in the sensing element  26  and provides an indication of the capacitance between the capacitive sensor  14  and the liquid LQ in the container  2 . 
         [0054]    With reference to  FIG. 6 , the electronic control unit  15  comprises a second processor  29  coupled to system memory  30  and powered by two batteries  31 . The electronic control unit  15  is mounted to a front face  32  of the cup-shaped member  20  and the batteries  31  are housed in a sleeve  33  beneath the electronic control unit  15 . The batteries  31  are disposed remote from the capacitive sensor  14  to reduce interference. A brace  34  is provided to support the support member  22  and the sleeve  33 . The brace  34  also forms a stop for limiting forward travel of the lever  24 . 
         [0055]    A set of computational instructions is stored on the system memory  30 . When executed, the computational instructions cause the second processor  29  to estimate the quantity of the liquid LQ in the container  2  in dependence on the received capacitance signal SIG 1 . The capacitance signal SIG 1  changes in proportion to changes in the quantity of the liquid LQ in the container  2 . The second processor  29  cross-references the capacitance signal SIG 1  with a look-up table T stored in the system memory  30 . The look-up table T defines a lower signal threshold and an upper signal threshold. The lower signal threshold corresponds to a base capacitance measurement, for example corresponding to a minimum quantity of liquid LQ in the container  2  or when the container  2  is empty. The upper signal threshold corresponds to a maximum quantity of liquid LQ in the container  2 , for example when the container  2  is full of liquid LQ. In the present embodiment the upper signal threshold corresponds to approximately 600 ml of liquid LQ in the container  2 . The upper and lower signal thresholds can be predefined, for example by the manufacturer of the dispenser  1 . Alternatively, or in addition, the upper and lower signal thresholds can be determined dynamically, for example by calibrating the dispenser  1  when a container  2  full of the liquid LQ is installed. 
         [0056]    At least between said upper and lower signal thresholds, the quantity of liquid LQ in the container  2  is proportional to the capacitance signal SIG 1  received from the capacitive sensor  14 . The second processor  29  may, for example, be configured to continuously estimate the quantity of liquid LQ in direct proportion to the signal from the capacitive sensor  14 . Alternatively, the look-up table T may define a plurality of capacitance bands, each capacitance band corresponding to a sub-division of the total quantity of the liquid LQ in the container  2 . The look-up table T could, for example, define twelve (12) capacitance bands each corresponding to approximately 50 ml of the liquid LQ. It will be understood that the look-up table T may define less than or more than twelve (12) capacitance bands. Moreover, the capacitance bands may each correspond to a different quantity of liquid LQ. For example, each capacitance band may correspond to 10 ml, 25 ml, 75 ml or 100 ml of liquid LQ. The capacitance bands are defined between the upper and lower signal thresholds. The second processor  29  receives the capacitance signal SIG 1  and identifies the applicable capacitance band and outputs a corresponding quantity estimation signal SIG 2  indicating the estimated quantity of liquid LQ in the container  2 . 
         [0057]    In the present embodiment, the electronic control unit  15  is connected to a transmitter  35 . The transmitter  35  is a radio frequency transmitter having a so-called “pigtail” antenna  36 . The transmitter  35  is configured to transmit the quantity estimation signal SIG 2  to a base station  37  having a receiver  38 , as shown schematically in  FIG. 6 . The base station  37  is operative to monitor the quantity of the liquid LQ in the container  2 . The electronic control unit  15  comprises a synchronization button  39  (shown in  FIG. 3 ) operable to synchronise the dispenser  1  with the base station  37 . A unique identifier code may be defined in the system memory  30  to allow the base station to identify the dispenser  1  and to monitor the quantity of liquid LQ in the container  2 . The synchronization button  39  is intended for use by a service attendant, for example when the dispenser  1  is first installed, and is covered when the cover  19  is in its closed position. 
         [0058]    The operation of the dispenser  1  will now be described with reference to the accompanying figures. The dispenser  1  is typically installed in a public washroom and is serviced periodically by a service attendant. The cover  19  of the dispenser  1  is opened and a full container  2  installed. The valve assembly  6  projects through the aperture  23  such that the dispensing nozzle  10  projects from the bottom of the housing  12  for dispensing liquid LQ. The bottom of the container  2  locates in the cup-shaped member  20  and is supported by the support member  22 . The bottom wall  3  of the container  2  engages the sensing element  26 . As the container  2  is introduced into the housing  12 , the sensing element  26  is deflected downwardly and is retained in position between the bottom wall  3  and the support member  22 . If required, the synchronization button  39  is depressed to synchronize the electronic control unit  15  with the base station. The cover  19  is then closed to secure the container  2  inside the dispenser  1 . 
         [0059]    The liquid LQ in the container  2  passes through the upper valve  7  and into the pumping chamber  9 . The lever  24  is actuated by a user to cause the actuating arm  25  to apply an actuating force to deform the resilient tubular member. A metered volume of the liquid LQ is dispensed from the pumping chamber  9  through the dispensing nozzle  10 . The lever  24  is released and returns to its standby position. An alternating voltage is supplied to the capacitive sensor  14  by the electronic control unit  15 . By measuring the current in the sensing element  26 , an indication of the capacitance between the capacitive sensor  14  and the remaining liquid LQ in the container  2  can be determined. The capacitive sensor  14  outputs a capacitance signal SIG 1  to the electronic control unit  15 . The electronic control unit  15  accesses a look-up table to estimate the quantity of liquid LQ remaining in the container in dependence on the capacitance signal SIG 1 . The electronic control unit  15  outputs the quantity estimation signal SIG 2  to the transmitter  35  for wireless transmission to the base station  37 . The base station  37  can thereby remotely monitor the quantity of liquid LQ remaining in the container  2  and schedule servicing when there is a predetermined percentage remaining. For example, the base station  37  may schedule servicing when there is 10% of the liquid LQ remaining in the container  2 . The base station  37  may be located on-site or at a separate location. The base station  37  may communicate with the dispenser  1  over a network, such as the internet. 
         [0060]    The liquid LQ dispensed from the dispenser  1  in the present embodiment is a liquid soap. The soap is stored in the container  2  in the form of a liquid. The liquid may foam as it is dispensed. For example, the liquid may be aerated as it is dispensed, or it may comprise a foaming agent. The liquid soap may be a gel or a cream. 
         [0061]    The dispenser  1  may optionally comprise a display unit to provide a visual indication of the amount of liquid LQ remaining. The display unit may comprise a liquid crystal display (LCD) configured to display the percentage of the liquid LQ remaining in the container  2 . 
         [0062]    A dispenser  1  in accordance with a further embodiment of the present invention is shown in  FIGS. 7 and 8 . The dispenser  1  is a variant of the previous embodiment and like reference numerals are used for like components. The capacitive sensor  14  and the support member  22  are modified in this embodiment and the description herein details these modifications. 
         [0063]    The dispenser  1  comprises a housing  12 , a dispensing actuator  13  and a capacitive sensor  14 . The housing  12  comprises a mounting plate  17 , a support frame  18  and a pivotally mounted cover  19 . The mounting plate  17  is adapted to be mounted to a wall to mount the dispenser  1 . The support frame  18  projects outwardly from the mounting plate  17  and is adapted to support the container  2 . The container  2  (not shown in  FIGS. 7 and 8 ) has the same configuration as the arrangement illustrated in  FIGS. 1 to 6 . In particular, the container  2  is a one-piece body comprising a bottom wall  3 , a sidewall  4  and a top wall  5 . The container  2  is moulded from a plastics material and contains a liquid LQ. The liquid LQ is a liquid soap and the container  2  can be removed and replaced to service the dispenser  1 . 
         [0064]    The capacitive sensor  14  comprises a sensing element  26  coupled to an electronic control unit  15  (not shown in  FIGS. 7 and 8 ). The sensing element  26  is adapted to locate against an underside of the bottom wall  3  of the container  2 . As shown in  FIG. 8 , the sensing element  26  is formed from an electrically conductive element, such as a metal wire, comprising first, second and third curved sections  26 A-C arranged in a generally W-shaped configuration. The sensing element  26  is adapted to engage an underside of the bottom wall  3  to establish direct physical contact with the container  2 . The sensing element  26  is disposed between the underside of the bottom wall  3  and the support member  22 . The bottom wall  3  of the container  2  is non-conductive (i.e., dielectric) and forms an electrical insulator between the sensing element  26  and the liquid LQ which are electrically conductive. 
         [0065]    The support member  22  is arranged to support the container  2  in the dispenser  1 . The support member  22  is fixedly mounted in the housing  12  and forms a fixed platform for the container  2 . In the present embodiment, the support member  22  comprises a central region  40 , a first lateral sidewall  41 , a second lateral sidewall  42 , a first protrusion  43  and a second protrusion  44 . The lateral sidewalls  41 ,  42  and the protrusions  43 ,  44  are arranged to engage the lower surface of the bottom wall  3  to support the container  2 . The first, second and third curved sections  26 A-C of the sensing element  26  project upwardly above the protrusions  43 ,  44  to contact the underside of the container  2 . The central region  40  forms a recess in which the sensing element  26  is mounted. A mounting plate  45  is fastened to the top of the support member  22 . The mounting plate  45  comprises laterally extending mounting lugs  46  for fixedly mounting the sensing element  26  to the support member  22 . The sensor mounting member  45  also comprises a slot  46  in which the synchronization button  39  is disposed. 
         [0066]    A capacitive coupling is established between the sensing element  26  and the liquid LQ in the container  2 . The capacitive sensor  14  is operative to measure the capacitance between the sensing element and the liquid LQ in the container  2 . In use, an electrical current is supplied to the sensing element  26 . The electrical current in the sensing element  26  is affected by the quantity of liquid LQ in the container  2 . The electrical current in the sensing element  26  is measured to provide an indication of the capacitance. In particular, the electrical current in the sensing element  26  is output to the operational amplifier of the first processor  28 . The amplified signal is converted by the analogue-to-digital converter to a digital signal which represents the capacitance signal SIG 1 . The capacitance signal SIG 1  provides an indication of the capacitance between the capacitive sensor  14  and the liquid LQ in the container  2 . The capacitive sensor  14  may operate continuously; or may operate intermittently, for example each time the actuator  14  is operated or on a predetermined time schedule. 
         [0067]    The capacitance signal SIG 1  is output to the second processor  29  which is coupled to the system memory  30 . The second processor  29  estimates the quantity of the liquid LQ in the container  2  in dependence on the received capacitance signal SIG 1 . The capacitance signal SIG 1  changes in proportion to changes in the quantity of the liquid LQ in the container  2 . The second processor  29  cross-references the capacitance signal SIG 1  with a look-up table T stored in the system memory  30 . A lower signal threshold and an upper signal threshold are predefined. The lower signal threshold corresponds to a lower detectable quantity of liquid LQ in the container  2 ; and the upper signal threshold corresponds to an upper detectable quantity of liquid LQ in the container  2 . In the present embodiment the detected capacitance between the capacitive sensor  14  and the liquid LQ is expressed as a numerical capacitive level count. A value of 50,000 counts corresponds to a liquid level of 100% (i.e., the container  2  is full of said liquid LQ); and a value of 40,000 counts corresponds to a liquid level of 5% (i.e., the container  2  is substantially empty). The upper signal threshold is defined as 50,000 counts and the lower signal threshold is defined as 40,000 counts. A delta (A) of 10,000 counts represents the difference between the upper and lower signal thresholds. At least between said upper and lower signal thresholds, the quantity of liquid LQ in the container  2  is proportional to the capacitance signal SIG 1  received from the capacitive sensor  14 . The operation of the electronic control unit  15  to monitor the quantity of liquid LQ in the container  2  is substantially unchanged from the previous embodiment. 
         [0068]    It will be appreciated that various changes and modifications can be made to the dispenser  1  described herein without departing from the scope of the present application. For example, the second processor  29  may apply a mathematical function to the received capacitance signal SIG  1  to estimate the quantity of the liquid LQ in the container  2 . The mathematical function may comprise a linear function or a polynomial function which defines the relationship between the received capacitance signal SIG 1  and the quantity of liquid LQ in the container  2 . 
         [0069]    The electronic control unit  15  may optionally be calibrated when the full container  2  is installed. The calibration could, for example, be performed automatically when the synchronization button  39  is depressed. 
         [0070]    The conductive properties of different types of liquid LQ may vary resulting in variations in the measured capacitance. To compensate for any such variations, the dispenser  1  may be calibrated for a particular type and/or composition of liquid LQ. Alternatively, or in addition, the shape or composition of the container  2  may affect the measured capacitance. The dispenser  1  may be calibrated for a particular shape and/or composition of container  2 . 
         [0071]    The dispenser  1  could be configured to operate in conjunction with a particular type of container  2  and/or liquid LQ, for example a proprietary container  2 . Alternatively, the dispenser  1  may be used with a plurality of different containers  2 . The dispenser  1  may be re-calibrated for use with different containers  2 . A plurality of different look-up tables T may be predefined for use with different containers  2  and/or liquids LQ. The electronic control unit  15  may comprise means for selecting a particular look-up table T. For example, one or more switch or controller may be provided to configure the electronic control unit  15  for use in different applications. 
         [0072]    In an alternate embodiment, the functions of the first and second processors  28 ,  29  may be performed by a single processor. For example, the functions of the first and second processors  28 ,  29  may both be performed by a single processor in the sensor control unit  27 . In this arrangement, the sensor control unit  27  may estimate the quantity of liquid LQ remaining in the container  2  in dependence on the capacitance signal SIG 1 . The sensor control unit  27  would output a quantity estimation signal SIG 2 . 
         [0073]    In a further alternative, the capacitance signal SIG 1  may be output from the capacitive sensor  14  to the base station  37  to be processed remotely from the dispenser  1 . The base station  37  may estimate the quantity of liquid LQ in the container  2  in dependence on the received capacitance signal SIG 1 . The base station  37  may schedule servicing of the dispenser  1  in dependence on the estimated quantity of liquid LQ. The base station  37  may be coupled to a plurality of like dispensers  1 . 
         [0074]    The invention has been described herein has been described with reference to a dispenser  1  for dispensing a liquid LQ. It will be understood that the invention is not limited to this particular application. For example, the dispenser  1  could be used to dispense an anti-bacterial solution, a barrier cream or a moisturising cream. Further embodiments which are not related to washroom applications are also contemplated.