Abstract:
A method and apparatus for automatically calculating and controlling levels of a given chemical in a liquid from a liquid reservoir using colorimetry testing, the method comprising the steps of (i) collecting in an optical chamber a sample of liquid from a liquid reservoir; (ii) taking a calibration colorimetry A reading of the liquid sample, whereby a reference voltage value B representative of an acceptable limit of a known chemical is calculated and stored in a memory of a controller unit; (iii) releasing the liquid sample from the optical chamber; (iv) collecting in the optical chamber a further sample of liquid from the liquid reservoir; (v) adding a predetermined quantity of a reagent to the further sample in the optical chamber, the reagent chosen as having properties making it react to the presence of the known chemical present or to be added to the liquid; (vi) taking a test colorimetry reading C of the further sample with the reagent added thereto and obtaining a voltage signal representative thereof, whereby a level of the known chemical is known with respect to the reference voltage value B; and (vii) adding a calculated quantity of the known chemical to the liquid reservoir in response to the calculated level of the known chemical in the further sample if the calculated level is below the reference voltage value B.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an automatic liquid analyser and quality controller and more particularly, but not exclusively, for use with swimming pools, spas and other reservoirs wherein a chemical admixed with a liquid requires to be monitored and maintained in predetermined quantity within the liquid.  
         BACKGROUND OF THE INVENTION  
         [0002]    Water basins and reservoirs are commonly found in the commercial and leisure industries under various forms, such as swimming pools, fish farming ponds, etc. maintaining a specific water quality is essential in many leisure or industrial applications. For instance, a water quality standard provides comfort and safety to swimmers using a swimming pool.  
           [0003]    Accordingly, water reservoirs often require periodic monitoring and chemical treatment in order to attain regulated quality levels. For example, it is a known practice to add a halogen such as chlorine to the water of a swimming pool to achieve an effective sterilization thereof. Many methods have thus been provided in order to quantify the level of chemicals in the water. One such method is referred to as colorimetry and consists of injecting a reagent in a sample of water which changes color in reaction to a given chemical (i.e. chlorine in the case of a swimming pool). This level of chemical may be interpreted from the intensity of light from a light source passing through the reagent/water mixture.  
           [0004]    One of the advantages of the colorimetry method resides in the fact that it is very simple and inexpensive to achieve. Canadian Patent No. 2,169,248, issued on Oct. 10, 1997 to Privé discloses an automatic chemical monitor and control system to be used mainly with swimming pools. This patent describes the use of colorimetry with samples of water extracted from the recirculating water line of a swimming pool in order to determine the level of treatment chemical and pH thereof. The system also injects chemicals in the water recirculation line in response to the variance between the calculated level of chemicals and a predetermined reference value.  
           [0005]    The above described patent provides a fully automated system which monitors the water quality and reacts to adjust the quality if it differs from predetermined quality values. However, the system of the above described patent involves costly and lengthy adaptation in order to provide a new or an existing pool therewith, as it must be connected to the recirculating water line. It is also pointed out that the system of the above described patent has a predetermined reference value, and thus no autocalibration of this system is achieved.  
           [0006]    U.S. Pat. No. 6,113,858, issued on Sep. 5, 2000 to Tang et al. discloses a monitor for continuous concentration measurements of liquid samples which uses colorimetry testing therefor. The monitor comprises a cavity at a bottom thereof being open to the liquid reservoir whose liquid is to be analysed. A light emitter and a light detector are face to face on opposed walls of the cavity, whereby concentration of a chemical in the liquid may be determined by sensing the intensity of a light signal passing therethrough when a reagent has been added to the sample. The reagent, stored in the monitor, is injected in the sample. However, the cavity is open whereby the accuracy of the signal is questioned. Furthermore, no calibration is involved and the cavity is also subject to daylight as it is open to the reservoir.  
         SUMMARY OF THE INVENTION  
         [0007]    It is a feature of the present invention to provide an automatic liquid analyser and quality controller which substantially overcomes the drawbacks of the prior art.  
           [0008]    It is a further feature of the present invention to provide an automatic liquid analyser and quality controller having a rinsing cycle for ensuring proper reading conditions of colorimetry equipment.  
           [0009]    It is still a further feature of the present invention to provide a method for automatically analyzing water and for automatically controlling its quality which substantially overcomes the drawbacks of the prior art,  
           [0010]    According to the above features, from a broad aspect, the present invention provides a method for automatically calculating levels of a given chemical in a liquid from a liquid reservoir using colorimetry testing, comprising the steps of (i) collecting in an optical chamber a sample of liquid from a liquid reservoir; (ii) taking a calibration colorimetry reading of the liquid sample, whereby a reference voltage value representative of an acceptable limit of a known chemical is calculated and stored in a memory of a controller unit; (iii) releasing the liquid sample from the optical chamber; (iv) collecting in the optical chamber a further sample of liquid from the liquid reservoir, (v) adding a predetermined quantity of a reagent to the further sample in the chamber, the reagent chosen as having properties making it react to the presence of the known chemical present or to be added to the liquid; and (vi) taking a test colorimetry reading of the further sample with the reagent added thereto and obtaining a voltage signal representative thereof, whereby a level of the known chemical in the liquid is known with respect to the reference voltage value.  
           [0011]    According to a further broad aspect of the present invention, there is provided an automatic liquid analyser for calculating levels of a given chemical in a liquid from a liquid reservoir using colorimetry testing, the automatic liquid analyser comprising an optical chamber for receiving liquid samples therein. The optical chamber is connected to a liquid reservoir by a liquid inlet line, and is connected to a drain by a sample outlet line. A pump is mounted on the liquid inlet line and is adapted for conveying samples of liquid from the liquid reservoir to the optical chamber. A valve is mounted on the sample outlet line for opening and closing same so as to release and retain liquid in the optical chamber. A first reagent reservoir stores a reagent. A reagent line extends between the reagent reservoir and the optical chamber. A second pump is mounted on the reagent line and is adapted for conveying predetermined quantities of the reagent from the reagent reservoir to the optical chamber. A light source is mounted to the optical chamber for emitting a light signal for colorimetry testing. A light detector is mounted to the optical chamber opposite the light source and aligned therewith for receiving the light signal for colorimetry testing. A controller unit calculates the level of a known chemical according to intensity of the light signal detected and for controlling the automatic liquid analyser according to the above described method.  
           [0012]    According to a still further broad aspect of the present invention, there is provided a method for automatically calculating and controlling levels of a given chemical in a liquid from a liquid reservoir using colorimetry testing, the method comprising the steps of (i) collecting in an optical chamber a sample of liquid from a liquid reservoir; (ii) taking a calibration colorimetry reading of the liquid sample, whereby a reference voltage value representative of an acceptable limit of a known chemical is calculated and stored in a memory of a controller unit; (iii) releasing the liquid sample from the optical chamber; (iv) collecting in the optical chanter a further sample of liquid from the liquid reservoir; (v) adding a predetermined quantity of a reagent to the further sample in the optical chamber, the reagent chosen as having properties making it react to the presence of the known chemical present or to be added to the liquid; (vi) taking a test colorimetry reading of the further sample with the reagent added thereto and obtaining a voltage signal representative thereof, whereby a level of the known chemical is calculated with respect to the reference voltage value; and (vii) adding a calculated quantity of the known chemical to the liquid reservoir in response to the calculated level of the known chemical in the further sample if the calculated level is below the reference voltage value.  
           [0013]    According to a still further broad aspect of the present invention, there is provided an automatic liquid analyser and quality controller for controlling levels of a given chemical in a liquid from a liquid reservoir using colorimetry testing. The automatic liquid analyser and quality controller comprises an optical chamber for receiving liquid samples therein. The optical chamber is connected to a liquid reservoir by a liquid inlet line, and is connected to a drain by a sample outlet line. A first pump is mounted on the liquid inlet line and is adapted for conveying samples of liquid from the liquid reservoir to the optical chamber. A valve is mounted on the sample outlet line for opening and closing same so as to release and retain liquid in the optical chamber. A first reagent reservoir stores a reagent. A reagent line extends between the reagent reservoir and the optical chamber. A second pump is mounted on the reagent line and is adapted for conveying predetermined quantities of the reagent from the reagent reservoir to the optical chamber. A light source is mounted to the optical chamber for emitting a light signal for colorimetry testing. A light detector is mounted to the optical chamber opposite the light source and aligned therewith for receiving the light signal for colorimetry testing. A chemical reservoir stores an amount of a known chemical. The chemical reservoir is adapted to be mounted to a portion of the liquid reservoir, and has conveying means extending therefrom to the portion of the liquid reservoir and is actuated by a motor for adding calculated quantities of the known chemical to the liquid reservoir. A controller unit calculates the level of the known chemical according to intensity of the light signal detected and controls the automatic liquid analyser and quality controller according to the above described method. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    A preferred embodiment of the present invention will now be described in detail having reference to the accompanying drawings in which:  
         [0015]    [0015]FIG. 1 is a schematic diagram of the automatic liquid analyser and quality controller of the present invention;  
         [0016]    [0016]FIG. 2 is a flow chart illustrating the operation of a controller unit of the present invention;  
         [0017]    [0017]FIG. 3 is a flow chart illustrating further steps of operation of the controller unit; and  
         [0018]    [0018]FIG. 4 is a side elevational view of an automatic chemical dispenser constructed in accordance with the present invention. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]    Referring to the drawings and, more particularly, to FIG. 1, an automatic liquid analyser and quality controller of the present invention is generally shown at  10 . The automatic liquid analyser and quality controller  10  is connected to a liquid reservoir such as a swimming pool P provided with a typical skimmer S by a liquid inlet line  12 . The automatic liquid analyser and quality controller  10  has an optical chamber  14  which is connected to the skimmer S by the liquid inlet line  12 . A pump  16  ensures the flow of water from the skimmer S to the optical chamber  14  through the liquid inlet line  12 . The automatic liquid analyser and quality controller  10  also has a reagent reservoir  18  which is connected to the optical chamber  14  through a reagent line  20 . A pump  22  ensures the flow of reagent from the reagent reservoir  18  to the optical chamber  14  through the reagent line  20 . The reagent has a property by which it changes the color of a liquid sample in the presence of a chemical in the liquid sample. For instance, orthotolidine reacts to the presence of chlorine in a water sample. Also, further reagent reservoirs may be provided with the automatic liquid analyser and quality controller  10  to control other criteria of a liquid sample with the same automatic liquid analyser and quality controller  10 . For instance, pH may also be monitored by the automatic liquid analyser and quality controller  10 . It is pointed out that mechanisms equivalent to pumps (i.e. in reference to pumps  16  and  22 ) may be provided in order to achieve the conveying of liquid samples to the optical chamber  14  (e.g. motor with an endless screw, gravity feeding valve, etc.). The reagent reservoir  18  is provided with an internal or external detector (not shown) to signal to the controller unit  32  when the reservoir  11  is close to being emptied. The controller unit  32  will activate a visible or audible alarm to indicate the reagent needs to be added.  
         [0020]    A solution outlet line  24  is connected to a bottom wall of the optical chamber  14  to provide an outlet for liquid captured in the optical chamber  14 . The flow of liquid through the solution outlet line  24  is controlled by a valve  26  connected thereto. When the valve  26  is in an open position, the liquid in the solution outlet line  24  is drained through line  24 ′. When the valve is in a closed position, liquid is captive in the optical chamber  14 . It is pointed out that the valve  26  is a 2-way solenoid valve or the like.  
         [0021]    A light source  28  and a light detector  30  (e.g. a photocell, etc.) are secured to side walls  14 ′ of the optical chamber  14  so as to be positioned opposite and in alignment with one another. Consequently, light emitted from the light source  28  (e.g. white or colored light) is sensed by the light detector  30 . It is pointed out that the side walls  14 ′ of the optical chamber  14  are preferably opaque, whereby the interior of the optical chamber  14  is isolated from external light, such that the only light emerging in the optical chamber  14  and sensed by the light detector  30  is emitted by the light source  28 .  
         [0022]    The automatic liquid analyser and quality controller  10  also comprises a controller unit  32 . As shown in FIG. 1, the controller unit  32  is wired to pumps  16  and  22  by the connector lines  17  and  23 , respectively. It is also connected to a port  26 ′ of the valve  26  by connector line  27 . The light source  28  is connected to the controller unit  32  by the connection cable  29 . The light detector  30  feeds signals to the controller unit  32  by its cable connection  31 . The controller unit  32  has an integrated control circuit incorporating an IC chip. It also controls a motor  34  through its connection  34 ′. The controller unit  32  may comprise elements such as an analogue to digital converter, a counter, an alarm, a display screen and a timer  32 ′. This will be described in further detail hereinafter.  
         [0023]    The controller unit  32  is programed to control the operation of the automatic liquid analyser and quality controller  10 . The controller unit  32  controls the pump  16  to admit water from the skimmer S of the pool P in the optical chamber  14 . It also controls the valve  26  between its open and closed positions. Consequently, by closing the valve  26 , and by activating the pump  16 , the optical chamber  14  may be filled with water from the skimmer S through the liquid inlet line  12 . It is pointed out that the optical chamber  14  may be provided with vent holes having check valves (not shown) at a top thereof in order to expel air for the water to fill the optical chamber  14  when the valve  26  is closed. The pump  16  is also actuated by the controller unit  32  when the valve  26  is opened so as to rinse the optical chamber  14  after it has been evacuated of its contents, and the rinse water injected by the pump  16  will exit through the solution outlet line  24  to the drain.  
         [0024]    The controller unit  32  also controls the pump  22  to inject reagent  18 , from the reagent reservoir  18  into the optical chamber  14 , through the reagent line  20 . The amount of reagent  18 ′ is controlled by the operating drive of the pump  22  to dispense a predetermined quantity of drops of reagent  18 ′. Consequently, predetermined quantities of water from the skimmer S and reagent  18 ′ from the reagent reservoir  18  are injected in the optical chamber  14 , whereby colorimetry testing may be achieved.  
         [0025]    Accordingly, the controller unit  32  may quantify the level of coloration of the mixture in the optical chamber  14  by emitting light from the light source  28  and quantitatively sensing the signals from the light detector  30 . In response thereto, if, for instance, the chlorine level of the water sample is too low, the motor  34  may be actuated by the controller unit  32  whereby chlorine may be released in the skimmer S to raise the calculated low value.  
         [0026]    Referring now to FIG. 2, the steps of operation of the controller unit  32  are generally shown at  100 . According to step  102 , the controller unit  32  is in a standby state, whereby a period of time is determined for the controller unit  32  (e.g. programmable/presetable by an operator/user) to be in a standby state and is held by the timer  32 ′. If the automatic liquid analyser and quality controller  10  is wired for a first use, the standby period (i.e. set time delay) is at zero.  
         [0027]    According to step  104 , if the standby time is elapsed, the controller unit  32  will go to step  106 . Otherwise, the controller unit  32  will remain in standby until the set time delay has elapsed.  
         [0028]    According to step  106 , the optical chamber  14  is filled with water from the skimmer S. This is achieved by valve  26  being closed by the controller unit  32  and the pump  16  being actuated. The controller unit  32  may be programmed in order to operate the pump  16  during step  106  such that the optical chamber  14  is filled up to a predetermined level, whereby a predetermined volume of water is in the optical chamber  14 .  
         [0029]    According to step  108 , a colorimetry reference reading is taken by the controller unit  32 . This is achieved by the controller unit  32  actuating the light source  28  to emit light through the liquid in the optical chamber  14 . The light will be sensed by the light detector  30 . It is pointed out that the controller unit  32  is provided with the necessary circuitry in order to interpret the detected light signals. For instance, the controller unit  32  may comprise an analogue to digital converter (not shown) in order to convert the analogue voltage value to a digital value to treat the signals.  
         [0030]    The colorimetry reference reading taken at step  108  (i.e. in the form of a voltage signal) is stored as a digital signal value by the controller unit  32 . The step  108  ensures the self-calibration of the automatic liquid analyser and quality controller  10 . This is due to the fact that a water sample having a reagent added thereto will remain clear if it has little or no chemical such as chlorine therein. By taking a reading of a water sample to which no reagent has been added, this sample will surely be clear and thus, will provide an output signal equivalent to a water sample to which reagent has been added but without any chemical therein and thus not reacting to the reagent, A differential voltage value (B-A) between a colorimetry reading A of a sample without chemical (and thus not reacting) and a colorimetry reading B of a sample having chemical at the limit of the level of acceptability according to given standards is known and programmed in the controller unit  32 . Thus, the reference colorimetry reading taken at step  108  is equivalent to the colorimetry reading A, whereby B can be calculated. Finally, it is pointed out that when undergoing the step  108  in a subsequent liquid sample analysis, the reference value stored will be replaced by the reference value of the subsequent reference reading,  
         [0031]    According to step  110 , the optical chamber  14  is emptied of the water sample and is rinsed. This is achieved by the controller unit  32  opening valve  26  in order to release the water sample from the optical chamber  14  to the drain. Thereafter, the pump  16  is actuated to rinse the optical chamber  14  with water from the skimmer S. This rinsing water does not accumulate in the optical chamber  14  as the valve  26  remains open throughout the rinsing process and it is evacuated to the drain.  
         [0032]    According to step  112 , the optical chamber  14  is again filled with a water sample from the skimmer S. This step is similar to step  106 .  
         [0033]    According to step  114 , reagent is added to the water sample in the optical chamber  14 . This is achieved by the controller unit  32  actuating the pump  22  in order to extract a predetermined quantity of reagent from the reagent reservoir  18  to inject it in the optical chamber  14  through the reagent line  20 . The pump  22  is chosen in order to control with precision the quantity of reagent it injects in the optical chamber  14 . The reagent is chosen to react to a specific chemical in the water by changing color. For instance, orthotolidine reagent may be used to react to chlorine, as previously mentioned.  
         [0034]    According to step  116 , a colorimetry reading C is taken by the controller unit  32 , and this time with reagent added to the water sample, as mentioned in step  114 . Similarly to step  108 , the controller unit  32  controls the emission of a light signal by the light source  28  and the detected light passing through the reagent/water solution in the optical chamber  14  to the light detector  30  generates a signal which is quantitatively interpreted by the controller unit  32 . The light signal is preferably of with color and of a wave length compatible with the light detector  30 .  
         [0035]    According to step  118 , the colorimetry reading C taken at step  116  is compared to the value B calculated by the reference colorimetry reading A taken at step  108  and which has been stored in the memory of the IC chip of the controller unit  32 . If the colorimetry reading C of step  116  is above the value B calculated from the reference colorimetry reading A of step  108 , the controller unit  32  will go to step  120 , wherein the optical chamber  14  is emptied and rinsed, in a similar fashion to step  110 . Thereafter, the controller unit  32  will be put on standby according to a preset timer value. If the colorimetry reading is below the value B calculated from the reference colorimetry reading A of step  101 , the controller unit  32  will reach step  122 , wherein chemical (e.g. chlorine or bromine, etc.) is added to the skinner S. This is achieved by the controller unit  32  actuating the motor  34 , as shown in FIG. 1. Thereafter, the controller unit  32  will go to the step  120 , previously described, which consists in emptying and rinsing the optical chamber  14 .  
         [0036]    It is pointed out that FIG. 2 may also have its step  122  of adding chemical to the skimmer S removed therefrom in the event where a display screen is provided with the controller unit  32 . In this case, an operator can manually insert chemical to the liquid reservoir according to the displayed value. Furthermore, if the reading comparison of step  118  is outside the predetermined range, an alarm, whether it be visual or sound, may be actuated in order to inform the operator.  
         [0037]    The flow chart of FIG. 2, as described above, discloses simple steps of operation of the present invention. However, is has been thought to provide the controller unit  32  with an alarm system which will intervene if too many colorimetry readings  116  showing low levels of the given chemical are taken successively.  
         [0038]    Referring now to FIG. 3, a flow chart is shown illustrating the steps achieved by the controller unit  32  in another embodiment of the present invention. For clarity purposes, steps  102 ,  104 ,  106  and  108  have been removed from FIG. 3 as they represent the same steps as in FIG. 2.  
         [0039]    According to stop  110 , the optical chamber  14  is emptied and rinsed from the water sample used for the reference colorimetry reading A of step  108 .  
         [0040]    According to step  112 , the optical chamber  14  is tilled with water from the skimmer S. This is similar to step  112  of FIG. 2.  
         [0041]    According to step  114 , reagent is added to the water in the optical chamber  14 . This is similar to step  114  of FIG. 2,  
         [0042]    According to step  116 , a colorimetry reading C is taken by the controller unit  32 . This is similar to step  116  of FIG. 2.  
         [0043]    According to step  118 , the colorimetry reading C of step  116  is compared to the value B calculated from the reference colorimetry reading A of step  108 . If the reading C is above the value B calculated from the reference colorimetry reading A taken at step  108 , the controller unit  32  will go to step  118 A. If the colorimetry reading C of step  116  is below the value B calculated from the reference colorimetry reading A of step  108 , the controller unit  32  will go to step  118 C.  
         [0044]    According to step  118 A, if the previous colorimetry reading C taken was low, the controller unit  32  will go to step  130 A. This involves that the controller unit  32  comprises a counter which accounts series of successively low colorimetry readings C taken at step  116 . In doing so, the controller unit  32  ensures that an operator is alarmed (as will be explairned hereinafter) if, upon a few successive additions of chemical to the skimmer S, the chemical is still not detected, in which case there may be a problem with the automatic liquid analyser and quality controller  10 . It is pointed out that this requires that the counter is reset for each positive colorimetry reading taken at  116 , which will thus reach step  118 A. Therefore, the step  120  of emptying and rinsing the optical chamber  14  may involve having the controller unit  32  resetting the counter to zero. As shown in FIG. 3, steps  118 A and  118 B are shown and step  118 B requires that W-1 colorimetry readings C are compared.  
         [0045]    This allows for a programmer of the controller unit  32  to set an alarm step according to the number of colorimetry readings C taken. For instance, if more than one colorimetry reading taken at  116  are successively low, it may be required that the standby time be shortened. Therefore, steps  130 A and  130 B show that standby time of the controller unit  32  may be adjusted in accordance with the number of colorimetry readings taken. Ultimately, if too many colorimetry readings are successively low (e.g. W low successive readings), an alarm may be actuated. This is achieved by providing  118 C which interprets the number of successively low colorimetry readings taken when the controller unit  32  requires that chemical is added to the skinner S, which is shown at step  122 . In FIG. 3, it is illustrated that if the number of colorimetry readings taken is of W, the alarm  140  will be actuated.  
         [0046]    According to step  124 , the optical chamber  14  is emptied and rinsed.  
         [0047]    Referring now to FIG. 4, an automatic chemical reservoir is generally shown at  40 . The chemical reservoir  40  comprises the motor  34  which, as described above, is connected to the controller unit  32 . The chemical reservoir  40  further comprises a reservoir  42  having a constricted bottom portion  44  and an opening  46  at a bottom thereof. The opening  46  of the reservoir  42  is disposed opposite an opening  48  of a cylinder  50  to release the chemical therein. An endless screw  51  is axially disposed in the cylinder  50  and is actuated by the motor  34 . The cylinder  50  is open to the skimmer S by conduit  52  which is connected to the opening  54  downstream of the reservoir  42 . Therefore, a chemical in the chemical reservoir  40  is processed through the cylinder  50  by the endless screw. The chemicals reach the conduit  52  to fall in the skimmer S. The reservoir  42  is also provided with an internal or external mechanical detector (not shown) to signal the controller unit  32  that chemical needs to be added thereto. The automatic chemical reservoir  40  could also comprise a solenoid operated piston to discharge a known quantity of chemical each discharge stroke of the piston. Other discharge systems may also be used.  
         [0048]    It is pointed out that the skimmer S is adapted for receiving the conduit  52 . Typically, a pool skimmer S is usually a circular cover having a hole in the middle thereof. Consequently, the automatic water controller of the present invention is adapted for being mounted quickly to the circular cover of the skimmer S. Therefore, the automatic liquid analyser and quality controller of the present invention may quickly be removed, thus making it portable. Also, the chemical reservoir  40  may be provided with a cover already mounted to the conduit  52 , in which case the cover on the skinner S may simply be removed in order to make place for the chemical reservoir  40 .  
         [0049]    Although the above description refers to the analysis of chlorine, it is also possible to measure the pH in a water reservoir and adjust it. It is of course understood that the automatic liquid analyser and quality controller of the present invention is not to be limited to swimming pool water analysis. The automatic liquid analyser and quality controller can be integrated in a liquid treatment system of a fish hatchery, a food washing liquid, and the like, to automatically add disinfectant products and stabilizers other than chlorine. The liquid analysed could be potable water in a water treatment reservoir and the function of the automatic liquid analyser and quality controller could be to prevent waste in chemical additives to a fluid mixture. The liquid could also be a soft drink or all sorts of bottled liquids where the present invention may be useful in controlling some chemical of its composition.  
         [0050]    It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims.