Abstract:
An apparatus includes a detecting electrode, a liquid sensing module, and a connecting means. The detecting electrode is attached to an outer surface of an intravenous drip container. The liquid sensing module includes a clock generator generating a clock signal, a waveform generating circuit coupled to the detecting electrode to generate an analog driving signal by using the clock signal, a grounding electrode grounded through the waveform generating circuit, an analog-to-digital converter converting the analog driving signal to a digital voltage signal, and a capacitance determining circuit receiving the digital voltage signal to determine a value of a capacitance of a capacitor formed by the detecting electrode and the grounding electrode. The connecting means connects the detecting electrode to the liquid sensing module.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to an apparatus for detecting the liquid level, remaining liquid quantity, and dripping speed of an intravenous bag (or bottle or container). 
         [0003]    2. Description of the Related Art 
         [0004]    Supplying medicine and nutritional supplements to patients via drip injection is a very common medical treatment in a medical process in a hospital. However, during the drip injection process, health care workers and patients have to take note, at frequent intervals, of the height of the liquid in the dripping bottle. If health care workers and patients fail to notice that the liquid in the dripping bottle has been depleted, vascular obstruction or other emergency situations can result. 
         [0005]    In view of this, at present, health care workers and patients can be warned by a suitable detecting device if the liquid in the dripping bottle is depleted or the height of liquid level in the dripping bottle is too low. Such a detecting device can monitor the drip injection process and thus reduce a load on health care workers and patients during the drip injection process and, accordingly, raise the quality of patient safety and health care. 
         [0006]    Taiwan Patent No. M360703 discloses a detecting device, wherein the liquid level in the dripping bottle is detected by two infrared sensors. When the height of the liquid level is lower than a predetermined value, a warning message is sent to inform health care workers. 
         [0007]    However, the detection of the liquid level in the dripping bottle by such a detecting device is not satisfactorily accurate. Furthermore, the detecting device can only detect the liquid level but cannot detect the remaining liquid quantity and the dripping speed of the dripping bottle, both of which are also important metrics for medical care. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The invention provides an apparatus for detecting a liquid level in an intravenous drip container. The apparatus in accordance with an exemplary embodiment of the invention includes a capacitor, a clock generator, a waveform generating circuit, an analog-to-digital converter, a capacitance determining circuit, and a processor. The capacitor includes a detecting electrode attached to an outer surface of the intravenous drip container, and a grounding electrode. The clock generator generates a clock signal. The waveform generating circuit is coupled to the detecting electrode to generate an analog driving signal by using the clock signal. The analog-to-digital converter converts the analog driving signal to a digital voltage signal. The capacitance determining circuit receives the digital voltage signal to determine a value of a capacitance of the capacitor. The processor converts the value of the capacitance into the liquid level in the intravenous drip container, and sends an alarm signal when the liquid level falls to a height of the detecting electrode. The grounding electrode is grounded through the waveform generating circuit and the processor. 
         [0009]    In another exemplary embodiment, the grounding electrode is disposed adjacent to the waveform generating circuit. 
         [0010]    In yet another exemplary embodiment, the processor includes a liquid level determining circuit configured to convert the value of the capacitance into the liquid level in the intravenous drip container, and a judgment circuit configured to judge the liquid level and send the alarm signal when the liquid level falls to the height of the detecting electrode. 
         [0011]    In another exemplary embodiment, the apparatus further includes a digital-to-analog circuit, a power amplifier, a radio frequency transmitter, and an antenna, wherein the alarm signal is converted from digital to analog by the digital-to-analog circuit, amplified by the power amplifier, and sent out by the radio frequency transmitter and the antenna. 
         [0012]    In yet another exemplary embodiment, the apparatus further includes an output terminal configured to send the alarm signal. 
         [0013]    In another exemplary embodiment, the analog driving signal can be a sine, square or triangular waveform. 
         [0014]    The invention also provides an apparatus for detecting a remaining liquid quantity in an intravenous drip container. The apparatus in accordance with an exemplary embodiment of the invention includes a capacitor, a clock generator, a waveform generating circuit, an analog-to-digital converter, a capacitance determining circuit, and a processor. The capacitor includes a detecting electrode attached to an outer surface of the intravenous drip container, and a grounding electrode. The clock generator generates a clock signal. The waveform generating circuit is coupled to the detecting electrode to generate an analog driving signal by using the clock signal. The analog-to-digital converter converts the analog driving signal to a digital voltage signal. The capacitance determining circuit receives the digital voltage signal to determine a value of a capacitance of the capacitor. The processor converts the value of the capacitance into the remaining liquid quantity in the intravenous drip container, judges the remaining liquid quantity, and sends an alarm signal when a liquid level in the intravenous drip container falls to a height of the detecting electrode. The grounding electrode is grounded through the waveform generating circuit and the processor. 
         [0015]    In another exemplary embodiment, the grounding electrode is disposed adjacent to the waveform generating circuit. 
         [0016]    In yet another exemplary embodiment, the processor includes a liquid quantity determining circuit configured to convert the value of the capacitance into the remaining liquid quantity in the intravenous drip container, and a judgment circuit configured to judge the remaining liquid quantity and sending out the alarm signal when the liquid level falls to the height of the detecting electrode. 
         [0017]    In another exemplary embodiment, the liquid quantity determining circuit includes a lookup table of non-equidistant intervals, by which the remaining liquid quantity is determined. 
         [0018]    In yet another exemplary embodiment, the apparatus further includes a digital-to-analog circuit, a power amplifier, a radio frequency transmitter, and an antenna, wherein the alarm signal is converted from digital to analog by the digital-to-analog circuit, amplified by the power amplifier, and sent out by the radio frequency transmitter and the antenna. 
         [0019]    In another exemplary embodiment, the apparatus further includes an output terminal configured to send out the alarm signal. 
         [0020]    In yet another exemplary embodiment, the analog driving signal can be a sine, square or triangular waveform. 
         [0021]    The invention further provides an apparatus for detecting a remaining liquid quantity and dripping speed of an intravenous drip container. The apparatus in accordance with an exemplary embodiment of the invention includes a capacitor, a clock generator, a waveform generating circuit, an analog-to-digital converter, a capacitance determining circuit, and a processor. The capacitor includes a detecting electrode attached to an outer surface of the intravenous drip container, and a grounding electrode. The clock generator generates a clock signal. The waveform generating circuit is coupled to the detecting electrode to generate an analog driving signal by using the clock signal. The analog-to-digital converter converts the analog driving signal to a digital voltage signal. The capacitance determining circuit receives the digital voltage signal to determine a value of a capacitance of the capacitor. The processor converts the value of the capacitance into the remaining liquid quantity in the intravenous drip container, determines the dripping speed by variation of the remaining liquid quantity, judges the remaining liquid quantity, and sends an alarm signal when a liquid level in the intravenous drip container falls to a height of the detecting electrode. The grounding electrode is grounded through the waveform generating circuit and the processor. 
         [0022]    In another exemplary embodiment, the grounding electrode is disposed adjacent to the waveform generating circuit. 
         [0023]    In yet another exemplary embodiment, the processor includes a liquid quantity determining circuit configured to convert the value of the capacitance into the remaining liquid quantity in the intravenous drip container, a dripping speed determining circuit configured to determine the dripping speed by the variation of the remaining liquid quantity, and a judgment circuit configured to judge the remaining liquid quantity and send the alarm signal when the liquid level falls to the height of the detecting electrode. 
         [0024]    In another exemplary embodiment, the liquid quantity determining circuit includes a lookup table of non-equidistant intervals, by which the remaining liquid quantity is determined. 
         [0025]    In yet another exemplary embodiment, the apparatus further includes a digital-to-analog circuit, a power amplifier, a radio frequency transmitter, and an antenna, wherein the alarm signal is converted from digital to analog by the digital-to-analog circuit, amplified by the power amplifier, and sent out by the radio frequency transmitter and the antenna. 
         [0026]    In another exemplary embodiment, the apparatus further includes an output terminal configured to send out the alarm signal. 
         [0027]    In yet another exemplary embodiment, the analog driving signal can be a sine, square or triangular waveform. 
         [0028]    The invention further provides an apparatus for detecting a liquid in an intravenous drip container. The apparatus in accordance with an exemplary embodiment of the invention includes a detecting electrode, a liquid sensing module, and a connecting means. The detecting electrode is attached to an outer surface of the intravenous drip container. The liquid sensing module includes a clock generator generating a clock signal, a waveform generating circuit coupled to the detecting electrode to generate an analog driving signal by using the clock signal, a grounding electrode grounded through the waveform generating circuit, an analog-to-digital converter configured to convert the analog driving signal to a digital voltage signal, and a capacitance determining circuit configured to receive the digital voltage signal to determine a value of a capacitance of a capacitor formed by the detecting electrode and the grounding electrode. The connecting means connects the detecting electrode to the liquid sensing module. 
         [0029]    In another exemplary embodiment, the connecting means is a clip. 
         [0030]    In yet another exemplary embodiment, the detecting electrode is T-shaped including a bottom portion attached to the outer surface of the intravenous drip container, and a top portion which is flexible to be held by the clip. 
         [0031]    In another exemplary embodiment, the apparatus further includes an electrically isolated case in which the liquid sensing module is disposed. 
         [0032]    In yet another exemplary embodiment, the apparatus further includes a processing and communication module configured to convert the value of the capacitance into a liquid level in the intravenous drip container, and to send an alarm signal when the liquid level falls to a height of the detecting electrode. 
         [0033]    In another exemplary embodiment, the apparatus further includes a processing and communication module configured to convert the value of the capacitance into a remaining liquid quantity in the intravenous drip container, judge the remaining liquid quantity, and send an alarm signal when a liquid level in the intravenous drip container falls down to a height of the detecting electrode. 
         [0034]    In yet another exemplary embodiment, the apparatus further includes a processing and communication module configured to convert the value of the capacitance into a remaining liquid quantity in the intravenous drip container, determine a dripping speed by variation of the remaining liquid quantity, judge the remaining liquid quantity, and send an alarm signal when a liquid level in the intravenous drip container falls to a height of the detecting electrode. 
         [0035]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0037]      FIG. 1  depicts an intravenous dripping bag and a detecting apparatus in accordance with a first embodiment of the invention; 
           [0038]      FIG. 2  is a schematic view of a detecting electrode of the detecting apparatus in accordance with the first embodiment of the invention; 
           [0039]      FIG. 3  is a block diagram of the detecting apparatus in accordance with the first embodiment of the invention; 
           [0040]      FIG. 4  is a block diagram of a detecting apparatus in accordance with a second embodiment of the invention; 
           [0041]      FIG. 5  shows a relationship between the remaining liquid quantity in an intravenous drip bag and a voltage signal sent to a capacitance determining circuit of the detecting apparatus in accordance with the second embodiment of the invention; 
           [0042]      FIG. 6  depicts an intravenous dripping bag and a measuring cylinder in accordance with a third embodiment of the invention; 
           [0043]      FIG. 7  is a block diagram of a detecting apparatus in accordance with a third embodiment of the invention; 
           [0044]      FIG. 8  is a block diagram of a detecting apparatus in accordance with a fourth embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
         [0046]    Referring to  FIG. 1 , in a first embodiment, a detecting apparatus  300  has a T-shaped detecting electrode  391 , a connecting means (e.g. a clip)  393 , an electrically isolated case  395 , and a box  396 . The box  396  and an intravenous drip bag (or bottle or container)  200  with a liquid (e.g. glucose solution) inside are supported by a drip stand  400 . The intravenous drip bag  200  is marked on its lower portion to locate the detecting electrode  391 . Referring to  FIG. 2 , the T-shaped detecting electrode  391  has a top portion  3911  and a bottom portion  3913 . The bottom portion  3913  of the detecting electrode  391  is attached to an outer surface of the intravenous drip bag  200 . The top portion  3911  of the detecting electrode  391  is flexible as indicated by an arrow A, to be held by the clip  393 . 
         [0047]    The detecting electrode  391  attached to the outer surface of the intravenous drip bag  200  and a grounding electrode  392  disposed in the electrically isolated case  395  serve as a capacitor  390 . The value of the capacitance of the capacitor  390  changes due to variation of the liquid level in the intravenous drip bag  200 . Therefore, the liquid level can be determined if the value of the capacitance of the capacitor  390  is obtained. The value of the capacitance C of the capacitor  390  can be obtained by the following formula: 
         [0000]        C =( I×T )| V    
         [0048]    wherein I is electric current, T is time, and V is voltage, all of which are measurable. 
         [0049]    During operation, the detecting apparatus  300  keeps detecting the liquid level in the intravenous drip bag  200  by the detecting electrode  391 . When the liquid level falls to the height of the detecting electrode  391 , the detecting apparatus  300  emits an alarm signal via wire or wireless transmission, indicative of a need for medical care. 
         [0050]      FIG. 3  is a block diagram of the detecting apparatus  300  of the first embodiment, wherein a liquid sensing module  301  is implemented in the case  395  of  FIG. 1 , and a processing and communication module  302  is implemented in the box  396 . In operation, the liquid sensing module  301  determines the value of the capacitance of the capacitor  390  through the detecting electrode  391 . The processing and communication module  302  converts the value of the capacitance of the capacitor  390  into the liquid level, and sends an alarm signal when the liquid level falls to the height of the detecting electrode  391 . A battery  357  provides power to a waveform generating circuit  320  and a clock generator  341  of the liquid sensing module  301 , and a processor  310  and another clock generator  343  of the processing and communication module  302 . 
         [0051]    More specifically, in the liquid sensing module  301 , a waveform generating circuit  320  receives a clock signal from a clock generator  341  to generate a driving signal S 1  of, e.g., a sine, square or triangular waveform. The driving signal S 1  is an analog voltage signal, varying dependant on the value of the capacitance of the capacitor  390 . The driving signal S 1  is converted into a digital voltage signal S 2  by an analog-to-digital converter  331  and sent to a capacitance determining circuit  311 . The value of the capacitance of the capacitor  390  is determined by the capacitance determining circuit  311  and sent to a processor  310  of the processing and communication module  302 . 
         [0052]    In the processing and communication module  302 , the clock generator  343  provides a clock signal for the operation of the processor  310 . The processor  310  includes a liquid level determining circuit  313  and a judgment circuit  315 , wherein the liquid level determining circuit  313  converts the value of the capacitance into the liquid level  220  in the container  200 , and the judgment circuit  315  judges the liquid level  220  in the container  200  and sends an alarm signal S 3  when the liquid level  220  falls to the height of the detecting electrode  391 . 
         [0053]    The alarm signal S 3  can be sent out via wire or wireless transmission. In wire transmission, the alarm signal S 3  is sent via output terminal  380 . In wireless transmission, the alarm signal S 3  is converted into an analog signal by a digital-to analog circuit  334 , amplified by a power amplifier  335 , and sent via a radio frequency (RF) transmitter  336  and an antenna  370 . 
         [0054]    Referring to  FIGS. 1 and 3 , the liquid sensing module  301  disposed in the case  395  includes the capacitance determining circuit  311 , the waveform generating circuit  320 , the analog-to-digital converter  331 , the clock generator  341 , and the grounding electrode  392 . Note that the grounding electrode  392  in the case  395  is disposed adjacent to the waveform generating circuit  320 , and electrically connected to ground  360  through the waveform generating circuit  320  and the processor  310 . Such an arrangement provides a stable and accurate measurement of the liquid level. 
         [0055]    In a second embodiment, the remaining liquid quantity in an intravenous drip bag (or bottle or container) is detected.  FIG. 4  is a block diagram of the detecting apparatus of the second embodiment, wherein a capacitor  490  includes a detecting electrode  491  attached to the outer surface of the intravenous drip bag  200  and a grounding electrode  492  spaced apart from the intravenous drip bag  200 . In operation, a liquid sensing module  401  determines the value of the capacitance of the capacitor  490  through the detecting electrode  491 . A processing and communication module  402  converts the value of the capacitance of the capacitor  490  into the remaining liquid quantity, and sends an alarm signal when the liquid level falls to the height of the detecting electrode  491 . A battery  457  provides power to a waveform generating circuit  420  and a clock generator  441  of the liquid sensing module  401 , and a processor  410  and another clock generator  443  of the processing and communication module  402 . 
         [0056]    More specifically, in the liquid sensing module  401 , the waveform generating circuit  420  receives a clock signal from a clock generator  441  to generate a driving signal S 4  of, e.g., a sine, square or triangular waveform. The driving signal S 4  is an analog voltage signal, varying dependant on the value of the capacitance of the capacitor  490 . The driving signal S 4  is converted into a digital voltage signal S 5  by an analog-to-digital converter  431  and sent to a capacitance determining circuit  411 . The value of the capacitance of the capacitor  490  is determined by the capacitance determining circuit  411  and sent to a processor  410  of the processing and communication module  402 . 
         [0057]    In the processing and communication module  402 , the clock generator  443  provides a clock signal for the operation of the processor  410 . The processor  410  includes a liquid quantity determining circuit  412  and a judgment circuit  415 , wherein the liquid quantity determining circuit  412  converts the value of the capacitance into the remaining liquid quantity in the intravenous drip bag  200 , and the judgment circuit  415  judges the remaining liquid quantity and sends an alarm signal S 6  when the liquid level  220  falls to the height of the detecting electrode  491 . 
         [0000]    
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Remaining Liquid 
                   
                 Voltage 
               
               
                 Quantity (ml) 
                 Interval 
                 (Stored Data) 
               
               
                   
               
             
             
               
                 500-410 
                 I 6   
                 V 0   
               
               
                   
                   
                 V 0  + 2 
               
               
                   
                   
                 V 0  + 4 
               
               
                   
                   
                 V 0  + 6 
               
               
                 409-320 
                 I 5   
                 V 1   
               
               
                   
                   
                 V 1  + 2 
               
               
                   
                   
                 V 1  + 4 
               
               
                 319-230 
                 I 4   
                 V 2   
               
               
                   
                   
                 V 2  + 2 
               
               
                 229-140 
                 I 3   
                 V 3   
               
               
                   
                   
                 V 3  + 2 
               
               
                 139-50  
                 I 2   
                 V 4   
               
               
                   
                   
                 V 4  + 2 
               
               
                   
                   
                 V 4  + 4 
               
               
                 49-0  
                 I 1   
                 V 5   
               
               
                   
                   
                 V 5  + 2 
               
               
                   
                   
                 V 5  + 4 
               
               
                   
                   
                 V 5  + 6 
               
               
                   
                   
                 V 6   
               
               
                   
               
             
          
         
       
     
         [0058]    Table 1 is a lookup table of the digital voltage signal S 5  and the remaining liquid quantity, which is measured in advance and stored in the liquid quantity determining circuit  412  for use during operation of the processor  410 . The variation of the remaining liquid quantity in the intravenous drip bag  200  is divided into six intervals I 1 -I 6 . In the sixth interval I 6 , for example, the remaining liquid quantity varies between 500-410 ml due to dripping, and the measured voltage signal S 5  includes V 0  for 500 ml, V 0 +2 for 470 ml, V 0 +4 for 440 ml, and V 0 +6 for 410 ml. Thus, the remaining liquid quantity at any time can be obtained by calculating the stored voltage data and, where appropriate, employing interpolation. For example, the obtained remaining liquid quantity is (500+470)/2 if the detected voltage signal is V 0 +1. The relationship between the remaining liquid quantity and the voltage signal S 5  is nonlinear, as shown in  FIG. 5 . Note that the six intervals I 1 -I 6  are non-equidistant, wherein the side intervals are wider than the intermediate intervals. That is, I 6 &gt;I 5 &gt;I 4  and I 1 &gt;I 2 &gt;I 3 . 
         [0059]    As described above, an alarm signal S 6  is sent out (or generated) by the processor  410  when the liquid level  220  falls to the height of the detecting electrode  491 . The alarm signal S 6  can be sent via wire or wireless transmission. In the case of wire transmission, the alarm signal S 6  is sent via an output terminal  480 . In the case of wireless transmission, the alarm signal S 6  is converted into an analog signal by a digital-to-analog circuit  434 , amplified by a power amplifier  435 , and sent out by a radio frequency (RF) transmitter  436  and an antenna  470 . 
         [0060]    Similar to that of the first embodiment, the grounding electrode  492  is disposed adjacent to the waveform generating circuit  420  in an electrically isolated case, and electrically connected to ground  460  through the waveform generating circuit  420  and the processor  410 . Such an arrangement provides a stable and accurate measurement of the remaining liquid quantity. 
         [0061]    Referring to  FIG. 6 , in a third embodiment, a measuring cylinder  810  is disposed under an intravenous drip bag  800  for adding medicine to the liquid or solution. A detecting electrode  591  is attached to the lower portion of the measuring cylinder  810 , detecting the remaining liquid quantity and dripping speed of the intravenous drip bag  800 . 
         [0062]      FIG. 7  is a block diagram of the detecting apparatus of the third embodiment, wherein a capacitor  590  includes a detecting electrode  591  attached to the measuring cylinder  810  and a grounding electrode  592  spaced apart from the measuring cylinder  810 . In operation, a liquid sensing module  501  determines the value of the capacitance of the capacitor  590  through the detecting electrode  591 . A processing and communication module  502  converts the value of the capacitance of the capacitor  590  into the remaining liquid quantity, calculates the dripping speed of the intravenous drip bag  800 , and sends out an alarm signal when the liquid level falls to the height of the detecting electrode  591 . A battery  557  provides power to a waveform generating circuit  520  and a clock generator  541  of the liquid sensing module  501 , and a processor  510  and another clock generator  543  of the processing and communication module  502 . 
         [0063]    More specifically, in the liquid sensing module  501 , the waveform generating circuit  520  receives a clock signal from a clock generator  541  to generate a driving signal S 7  of, e.g., a sine, square or triangular waveform. The driving signal S 7  is an analog voltage signal, varying dependant on the value of the capacitance of the capacitor  590 . The driving signal S 7  is converted into a digital voltage signal S 8  by an analog-to-digital converter  531  and sent to a capacitance determining circuit  511 . The value of the capacitance of the capacitor  590  is determined by the capacitance determining circuit  511  and sent to a processor  510 . 
         [0064]    In the processing and communication module  502 , the clock generator  543  provides a clock signal for the operation of the processor  510 . The processor  510  includes a liquid quantity determining circuit  512 , a dripping speed determining circuit  516 , and a judgment circuit  515 . The liquid quantity determining circuit  512  converts the value of the capacitance into the remaining liquid quantity in the intravenous drip bag  800 , and sends out a liquid quantity signal S 9 . The dripping speed determining circuit  516  receives the liquid quantity signal S 9 , calculates the dripping speed according to the variation of the liquid quantity, and sends a dripping speed signal S 10 . The judgment circuit  515  receives the dripping speed signal S 10  from the dripping speed determining circuit  516  and sends it via wire or wireless transmission for, e.g., nurse&#39;s monitoring. Also, the judgment circuit  415  receives the liquid quantity signal S 9  from the liquid quantity determining circuit  512  and sends an alarm signal S 11  when the liquid level  820  falls to the height of the detecting electrode  591 . The alarm signal S 11  is sent via an output terminal  580 . Alternatively, the alarm signal S 11  is converted into an analog signal by a digital-to analog circuit  534 , amplified by a power amplifier  535 , and sent out by a radio frequency (RF) transmitter  536  and an antenna  570 . 
         [0065]    Similar to those of the first and second embodiments, the grounding electrode  592  is disposed adjacent to the waveform generating circuit  520  in an electrically isolated case, and electrically connected to ground  560  through the waveform generating circuit  520  and the processor  510 . 
         [0066]    Referring to  FIG. 8 , in a fourth embodiment, a capacitor  690  includes a detecting electrode  691  and a grounding electrode  692 . The detecting electrode  691  is attached to the lower portion of a measuring cylinder  810 . A liquid sensing module  601  determines the value of the capacitance of the capacitor  690  through the detecting electrode  691 . A processing and communication module  602  converts the value of the capacitance of the capacitor  690  into the liquid level and the remaining liquid quantity, calculates the dripping speed of the intravenous drip bag  800 , and sends an alarm signal when the liquid level falls to the height of the detecting electrode  691 . A battery  657  provides power to a waveform generating circuit  620  and a clock generator  641  of the liquid sensing module  601 , and a processor  610  and another clock generator  643  of the processing and communication module  602 . 
         [0067]    More specifically, in the liquid sensing module  601 , the waveform generating circuit  620  receives a clock signal from a clock generator  641  to generate a driving signal S 12  of, e.g., a sine, square or triangular waveform. The driving signal S 12  is an analog voltage signal, varying dependant on the value of the capacitance of the capacitor  690 . The driving signal S 12  is converted into a digital voltage signal S 13  by an analog-to-digital converter  631  and sent to a capacitance determining circuit  611 . The value of the capacitance of the capacitor  690  is determined by the capacitance determining circuit  611  and sent to a processor  610 . 
         [0068]    In the processing and communication module  602 , the clock generator  643  provides a clock signal for the operation of the processor  610 . The processor  610  includes a liquid quantity determining circuit  612 , a liquid level determining circuit  613 , a dripping speed determining circuit  616 , and a judgment circuit  615 . The liquid level determining circuit  613  converts the value of the capacitance into the liquid level in the intravenous drip bag  800 , and sends a liquid level signal S 14 . The liquid quantity determining circuit  612  converts the value of the capacitance into the remaining liquid quantity in the intravenous drip bag  800 , and sends a liquid quantity signal S 15 . The dripping speed determining circuit  616  receives the liquid quantity signal S 15 , calculates the dripping speed according to the variation of the liquid quantity, and sends a dripping speed signal S 16 . The judgment circuit  615  receives the dripping speed signal S 16  from the dripping speed determining circuit  616  and sends it via wire or wireless transmission for, e.g., nurse&#39;s monitoring. Also, the judgment circuit  615  receives the liquid level signal S 14  from the liquid level determining circuit  613  and the liquid quantity signal S 15  from the liquid quantity determining circuit  612  and sends an alarm signal S 17  when the liquid level  820  falls to the height of the detecting electrode  691 . The alarm signal S 17  is sent out via output terminal  680 . Alternatively, the alarm signal S 17  is converted into an analog signal by a digital-to-analog circuit  634 , amplified by a power amplifier  635 , and sent via a radio frequency (RF) transmitter  636  and an antenna  670 . 
         [0069]    Similar to those of the first, second and third embodiments, the grounding electrode  692  is disposed adjacent to the waveform generating circuit  620  in an electrically isolated case, and electrically connected to ground  660  through the waveform generating circuit  620  and the processor  610 . 
         [0070]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.