Abstract:
Characteristics of a fluid are determined, in one embodiment, by flowing the fluid (which may contain charged particles) between a plurality of electrode pairs, applying respective DC voltages across at least two of the electrode pairs, and measuring resulting currents through the fluid at the respective electrode pairs. In one example, respective plates of the electrode pairs are configured so that they do not fully encircle one another.

Description:
BACKGROUND 
   Many factors contribute to the quality of a printing process. It can be appreciated that there is an ongoing desire to improve the quality of the print jobs. Therefore, monitoring one or more characteristics associated with a printing process may be desirable as this may promote higher quality print jobs. Nevertheless, monitoring certain characteristics may be difficult, such as one or more characteristics associated with a static pool of ink of a printing press, for example. 
   Various ink parameters strongly influence the performance of the press regarding print quality, operational stability and life time of consumables, therefore measuring and controlling such ink characteristics may be desirable. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     To the accomplishment of the foregoing and related ends, the following description and annexed drawings set forth in detail certain illustrative aspects and/or embodiments of the disclosure. These are indicative of but a few of the various ways in which one or more aspects and/or embodiments of the disclosure herein may be employed. Other aspects, advantages and/or novel features of the disclosure will become apparent from the following detailed description when considered in conjunction with the annexed drawings. 
       FIG. 1  is a functional schematic diagram of a laboratory type ink cell system that may be used to measure the conductivity of a static pool of ink. 
       FIG. 2  is a simplified functional schematic diagram of the basic operation of an Electro-Ink such as may be used in liquid electro-photography, comprising a dispersion of electrically chargeable particles in a dielectric liquid media. 
       FIG. 3  is a simplified schematic diagram of one exemplary embodiment of a conductivity and charge meter system configured to monitor and determine one or more characteristics of a flowing fluid, such as the conductivity of a flowing ink in accordance with one or more aspects and/or embodiments of the disclosure herein. 
       FIG. 4  is a simplified functional schematic diagram of a measuring system that may be used to measure a fluid characteristic, such as the conductivity of a static fluid specimen and an equation that may be used for such measurement. 
       FIGS. 5A and 5B  are plots of several fluid characteristics which may, for example, be measured and determined using the system embodiments of  FIGS. 1 ,  3 , and  4  in accordance with one or more aspects of the disclosure herein. 
       FIGS. 6A and 6B  are plots of an applied high field voltage and a corresponding conductivity response that may be obtained during a measurement of one or more fluid characteristics which may, for example, be determined using the system embodiments of  FIGS. 1 ,  3 , and  4  in accordance with one or more aspects of the disclosure herein. 
       FIG. 7  is a simplified schematic diagram of an exemplary embodiment of a conductivity and charge meter system configured to monitor and determine one or more characteristics of a flowing fluid, such as the conductivity of a flowing ink caused to flow between several electrode pairs using a rotating drum in accordance with one or more aspects and/or embodiments of the disclosure herein. 
       FIGS. 8-11  are flow diagrams illustrating one or more embodiments of an exemplary methodology operative to monitor and determine a conductivity of a flowing fluid based on current measurement data in accordance with one or more aspects of the disclosure herein. 
   

   DETAILED DESCRIPTION 
   One or more aspects of the present disclosure are described with reference to the drawings, wherein like reference numerals are generally utilized to refer to like elements throughout, and wherein the various structures are not necessarily drawn to scale. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects of the disclosure herein. It may be evident, however, that one or more aspects of the disclosure herein may be practiced with a lesser degree of these specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate describing one or more aspects of the disclosure herein. 
   Generally speaking, liquid electro-photography ink is a dispersion of electrically chargeable particles in a dielectric liquid media. Upon applying an electrical field, the particles become electrically charged and drift along the electrical field. Observation shows that the electrical conductivity of such an ink is strongly dependent on the strength of the applied electrical field—being low at low intensity field (typically below 50V/mm) and substantially higher at high intensity field (typically above 500V/mm). Accordingly, distinction is made between conductivities measured at low electrical field and high electrical field. 
   Observation also shows that when the ink particles are deprived from being replenished, as the particles drift to one of the electrodes, the measured current falls off reaching a constant value where substantially no particles are left (depleted) in the liquid between the electrodes. 
   For purposes of the disclosure, the following terms shall have the following meanings: 
   The term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” or “an”, “one or more of” and “at least one” can be used interchangeably herein. 
   “High field conductivity” is defined as the conductivity measured at the moment of applying the high intensity electrical field before particle depletion can take place. 
   “Low field conductivity” is defined as conductivity measured at low intensity field. 
   “DC conductivity” is defined as the conductivity measured after the current has leveled off because the measured current has achieved a substantially constant value. 
   “Particle conductivity” is defined as the difference between the high field conductivity of the ink and the low field conductivity as this difference is attributed to the particles and is referred to as “particle conductivity” as observation shows that after removing the particles from the ink (e.g., by separation in centrifuge) the remaining particle-less fluid essentially exhibits the same high field conductivity as the low field conductivity measured in the ink before removal of the particles. Particle conductivity is calculated as the product of the particle concentration (e.g., the number of particles per unit volume) multiplied by the charge carried by a single particle and by the mobility of the particles. 
   “Mobility” is defined as the ratio of the drift velocity of the particle to the applied electrical field strength. 
   The time integral of the current induced by high electrical field and corrected for the currents due to low field conductivity and DC conductivity represents the electrical charge carried by the particles. 
   Thus, the measurement of the different types of conductivity provides not only direct electrical properties but also valuable ink characteristics, such as charge concentration and particle concentration. 
   Referring to  FIG. 1 , for example, a laboratory type ink cell system  10  is illustrated that may be used to measure the conductivity of a static pool of ink. The ink comprises a dispersion  20  of ink particles  22  within a dielectric liquid media. The ink dispersion  20  that is to be measured is placed within an ink cell  24  between a pair of conductive electrodes  25  comprising a positive (+) electrode  26  and a negative (−) electrode  28  connected to a respective positive (+) terminal  32  and a negative (−) terminal  34  of a high voltage supply and low level current meter  30  of the ink cell system  10 . 
   In operation, a relatively high voltage from the voltage supply  30  is applied to the electrode pair  25  of the ink cell  24 . The ink particles  22  within the ink dispersion  20  are charged and briefly permit a current to conduct as the particles drift along the electric field between the electrodes  26  and  28 , as discussed above in regard to the “high field conductivity”. The current which conducts between the electrode pair  25  is measured by the low level current meter  30  and may be used to determine several characteristics associated with the conductivity of the ink dispersion  20  within the ink cell  24 . 
   As was also discussed above in regard to the “low field conductivity”, observation shows that when the ink particles  22  are deprived from being replenished (such as in the static ink cell  24 ), as the particles  22  drift to one of the electrodes, the measured current falls off reaching a constant value (e.g., “DC conductivity”) when few to no particles remain dispersed (depleted) within the liquid ink dispersion  20  between the electrodes  26 / 28 . 
     FIG. 2  further illustrates the basic operation of an Electro-Ink  50  such as may be used in liquid electro-photography. Liquid electro-photography ink  50  comprises a dispersion of electrically chargeable ink particles  22  in a dielectric liquid media or carrier liquid (e.g., imaging oil)  51 . The ink particles  22  of the Electro-Ink  50  further comprise a toner particle  52  having a pigment  54 , wherein the ink particles  22  may receive a negative charge  55  as a result of an electric field induced between a positive (+) electrode  56  and a negative (−) electrode  58 . If the fluid can be ionized, it may also contain positive ions  60  and/or negative ions  62  as a result of the induced electric field between the electrode pair. The Electro-Ink  50  may further contain a specific type of surface active agent known as charge directors  64 , which may be added to the ink to promote the ability of the ink particles  22  to acquire electrical charge. 
   As previously discussed, when the ink and the ink particles  22  are stationary or are otherwise deprived from being replenished (such as in the static ink cell  24  of  FIG. 1 ), the charged particles  22  (e.g., receiving negative charge  55 ) drift to one of the electrodes (e.g., negatively charged particles  22  are attracted to the positive electrode  56 ). When substantially all of the particles have drifted to the electrodes, the measured current falls off reaching a constant value (e.g., “DC conductivity”). 
   In one embodiment for the electro(-photo-)graphic process, one of the electrodes such as electrode  56  may be used as an “electro-photographic” plate or photo imaging plate (PIP)  56 , carrying a latent image in the form of a corresponding spatial distribution of electrical charges or potentials. In this embodiment, the other electrode  58  may then be used as the developer  58  that provides the ink  22  and pigment  54  in the toner particles  52 , which is then attracted to the spatial distribution of electrical charges representing the latent image. 
     FIG. 3  illustrates one exemplary embodiment of a conductivity and charge meter system  100  configured to monitor and facilitate the determination of one or more characteristics of a flowing fluid, such as the conductivity of a flowing ink  102  in accordance with one or more aspects and/or embodiments of the disclosure herein. 
   One embodiment of the conductivity and charge meter system  100  comprises three (or more) electrode pairs that are placed in a fluid (e.g., ink) containing charged particles. The fluid  101  is forced or otherwise caused to flow in a direction  102  between respective first and second plates (e.g.,  110   a / 110   b ,  120   a / 120   b , and  130   a / 130   b ) of the electrode pairs (e.g.  110 ,  120 , and  130 ). The electrode pairs (e.g.  110 ,  120 , and  130 ) are biased by a DC voltage V (e.g., applied by a positive (+) terminal  142  and a negative (−) terminal  144  of a voltage supply  140 ) such that by the time the fluid flows by the third (last) electrode pair  130  substantially all of the charged particles are removed from the fluid  101  (e.g., by being attracted to the second pair of plates  120   a / 120   b  of the second (middle/intermediate) electrode pair  120 ). While the fluid flows between the respective first and second plates (e.g.,  110   a / 110   b ,  120   a / 120   b , and  130   a / 130   b ) of the electrode pairs (e.g.  110 ,  120 , and  130 ), a corresponding DC current is monitored and measured between the plates of each of the electrode pairs, yielding a first current I 1  measured at current meter  1  ( 112 ), a second current I 2  measured at current meter  2  ( 122 ), and a third current I 3  measured at current meter  3  ( 132 ) based upon the applied DC voltage V from the voltage supply  140 . The DC current measurements I 1 , I 2 , and I 3  are then used to determine one or more conductivity characteristics or another such characteristic of the fluid based on a variety of factors and/or conditions associated with the measurement. Such factors and/or conditions may include, among others, the distance (d) between the plates, the cross-sectional area of the plates (A), and the applied voltage V, for example, as will be discussed further infra. 
   In this manner, and as the fluid  101  enters the conductivity and charge meter embodiment  100  of  FIG. 3  in flow direction  102 , an initial fluid conductivity measurement taken between the first and second plates  110   a / 110   b  of the first electrode pair  110  reflects a high concentration of charged particles in the fluid (e.g., for the “high field conductivity” measurement), while a fluid conductivity measurement taken between the first and second plates  130   a / 130   b  of the third (last) electrode pair  130  reflects a substantially low concentration of charged particles in the fluid (e.g., for the “DC conductivity” measurement). These conductivity measurements, as well as a “low field conductivity” measurement between the first and second plates  120   a / 120   b  of the second electrode pair  120  can then be used to determine additional characteristics of the fluid, which can affect the quality of the printing process. 
   Thus, in this example, a fluid such as ink is pumped or otherwise directed to flow between three (or more) electrode pairs, wherein the first electrode pair  110  has a short length in the direction  102  of the fluid flow, the second electrode pair  120  has a long length along the flow direction  102 , and the third electrode pair  130  has an arbitrary length along the flow direction  102 . For example, it will be appreciated that a peristaltic pump or another such pumping means may be used to pump the fluid between the plates of the three electrode pairs. By applying both a high and low value DC voltage (e.g., alternately) across the electrode pairs, two corresponding DC current values may be measured between the plates of the respective electrode pairs. 
   Further, the length of the first short electrode pair  110  is such that no significant particle depletion takes place during the time that the particles pass this electrode pair  110 , yet during such time, adequate charge collection occurs to enable current measurements therefrom. The length of electrode pair  120  is long enough to assure substantially total removal of the particles (referred to as polarization) from the fluid (e.g., ink) during passage of the fluid therebetween. Finally, the third electrode pair  130  need only be long enough to provide an adequate minimum charge collection for current measurement therefrom. 
   Based on the DC current measurements from each of the electrode pairs, one or more conductivity or other such characteristics of the fluid may be determined, including specific charge, mobility, and concentration of the charged particles, for example. The charged particles may or may not be native to the fluid, but such particles are generally an integral part of the fluid when manufactured for use in the electro(-photo-)graphic process, wherein the particles may also carry colorants and/or binders. 
     FIG. 4  illustrates a measuring system  200  that may be used to measure one or more characteristics such as the conductivity of a static fluid specimen and an equation that may be used for such measurement. Similar to the ink cell  10  of  FIG. 1 , the measuring system  200  of  FIG. 4  comprises a measuring cell  202  having a pair of electrodes  210  comprising a first electrode or plate  210   a  and a second electrode or plate  210   b  which are spaced apart by a distance d  216  on either side of the specimen  214  having a cross-sectional area A as seen by the plates  210   a / 210   b.    
   Voltage supply  240  is electrically connected to the plates  210   a / 210   b  of the measuring cell  202 , and supplies a voltage V  242  to the electrode pair  210 . As a result of the applied voltage  242 , a current I  212  can be measured between the first plate  210   a  and the second plate  210   b . Based upon the measured current I  212 , a conductivity a may be determined according to the equation: 
           σ   =         I   /   A       V   /   d       =       I   V     ·     d   A               
where
 
   σ=conductivity of the sample (in units of pmhO/cm) 
   I=current measured between the plates and thru the sample 
   A=cross-sectional area of the measured sample exposed to the plates 
   d=distance between the plates 
   V=voltage applied to the plates of the sample cell. 
     FIGS. 5A and 5B  illustrate exemplary plots  300  and  350 , respectively, of several fluid characteristics which may, for example, be measured and determined using the system embodiments of  FIGS. 1 ,  3 , and  4  in accordance with one or more aspects of the disclosure herein. 
   For example,  FIG. 5A  illustrates an exemplary plot  300  of the conductivity (in pmhO/cm) of a 2% fluid (the particles comprise 2% of the fluid) as a function of an applied voltage V per unit distance d, the voltage V applied to a sample cell such as sample cell  202  of  FIG. 4 . When the applied voltage V is applied at a lower voltage level, a “low field conductivity”  310  results, and when a higher voltage level is applied to the sample, a “high field conductivity”  320  is provided. The difference between the “high field conductivity”  320  and the “low field conductivity”  310  is known as the “particle conductivity”  330 . 
     FIG. 5B , illustrates another exemplary plot  350  of the conductivity (in pmhO/cm) of a fluid or carrier fluid without particles in the fluid sample (e.g., depleted of particles), the conductivity  360  measured as a function of an applied voltage V per unit distance d, the voltage V applied to a sample cell such as sample cell  202  of  FIG. 4 . 
     FIGS. 6A and 6B  illustrate exemplary plots  400  and  450 , respectively, of an applied high field voltage and a corresponding conductivity response that may be obtained during a measurement and determination of one or more fluid characteristics, for example, using the system embodiments of  FIGS. 1 ,  3 , and  4  in accordance with one or more aspects of the disclosure herein. 
   For example,  FIG. 6A  illustrates a high field voltage waveform  400 , wherein a high voltage is applied to a measurement cell such as sample cell  202  of  FIG. 4 . Prior to time t 0 , the voltage waveform  400  is at about 0 volts as shown at  410 . In response to this applied low voltage, and as shown in the plot  450  of  FIG. 6B , the conductivity (corresponding to the measured current) is also at about 0 pmhO/cm at  460 . 
   Between times t 0  and t 1 , the voltage  400  is stepped up to a “high field voltage” level of about 1500 volts, for example, at  420  across the plates of the cell having spacing distance d (e.g.,  216  of  FIG. 4 ) of about 1 mm, for example. Thus, in the embodiment, the electric field strength equals:
 
Electric field strength=1500V/1 mm=1.5V/μ
 
   In response to this step function of the high field voltage  420  applied at t 0 , the conductivity spikes to a “high field conductivity” level as shown at  470  in  FIG. 6B . As the high field voltage level is maintained at the  420  level, the charged particles (e.g.,  22  of  FIG. 2 ) within the fluid (e.g.,  51  of  FIG. 2 ) are substantially all attracted toward the oppositely charged electrode (e.g., positive electrode  56  of  FIG. 2 ) between times t 0  and t 1 . By time t 1  (e.g., after about 8 seconds), substantially all of the charged particles  22  have been depleted from the fluid and the conductivity of the fluid attains a substantially steady-state or “DC conductivity” level  480 . In this manner, numerous other fluid and particle characteristics may be measured and/or determined. 
   Accordingly,  FIG. 7  illustrates an exemplary embodiment of a conductivity and charge meter system  500  configured to monitor and determine one or more characteristics of a flowing fluid, such as ink, that is caused to flow between several electrode pairs by using a rotating drum  501 . 
   In  FIG. 7 , a drum  501  rotates within a fluid  502  (e.g., Electo-Ink  50  of  FIG. 2 ) containing charged particles (e.g.,  22  of  FIG. 2 ). As the drum  501  rotates in a direction  503  about a center point  504  which is connected to a positive terminal  542  of a voltage supply  540 , the fluid  502  is carried along the surface of the drum in a circular flow direction  506  between first and second plates  510   a / 510   b ,  520   a / 520   b , and  530   a / 530   b  of three respective electrode pairs  510 ,  520 , and  530 . In this example 500, the first plates  510   a ,  520   a , and  530   a  of the respective electrode pairs  510 ,  520 , and  530  are combined together into a single or common plate comprised of the surface of the drum  501 . 
   In particular, the fluid  502  is made to initially flow between a relatively short (e.g., having a length L 1 ) first pair of electrodes  510  comprising first and second plates  510   a  and  510   b  monitored by current meter  1  ( 512 ). Thereafter, the fluid  502  flows between a relatively long (e.g., having a length L 2 ) second pair of electrodes  520  comprising first and second plates  520   a  and  520   b  monitored by current meter  2  ( 522 ). Finally, the fluid  502  flows between a relatively arbitrary length (e.g., having a length L 3 ) third pair of electrodes  530  comprising first and second plates  530   a  and  530   b  monitored by current meter  3  ( 532 ). Accordingly, the three current meters  512 ,  522 , and  532  are connected to the negative terminal  544  of the voltage supply  540  in order to provide current measurements I 1 , I 2 , and I 3  which flow between the first and second plates of the respective electrode pairs  510 ,  520 , and  530  based upon an applied voltage V provided by voltage supply  540 . It will be appreciated that while three (3) electrode pairs are illustrated in  FIG. 7  (and  FIG. 3 ), that any suitable number of electrode pairs may be used. 
   In operation, the fluid  502  flowing between the first and second plates  510   a / 510   b  of the first electrode pair  1  ( 510 ) provides the first current measurement I 1  while the fluid  502  contains a maximum or full concentration of charged particles (e.g.,  22  of  FIG. 2 ). Accordingly, the length L 1  of the first electrode pair  510  is such that few to no charged particles polarize onto the drum  501  configured as the positive plate (e.g., first plate  510   a ,  520   a , and  530   a ) of the first, second, and third electrode pairs  510 ,  520 , and  530 , respectively. The length L 1  of the first electrode pair  510  is, however, sufficient to allow adequate charge collection to enable the I 1  current measurement. Accordingly, if a high field voltage V (e.g.,  420  of  FIG. 6A ) is applied by voltage supply  540  to the first electrode pair  1  ( 510 ), a “high field conductivity” (e.g.,  470  of  FIG. 6B ) may be determined based on the first current measurement I 1  of the first electrode pair  1  ( 510 ). 
   As the fluid  502  flows between the first and second plates  520   a / 520   b  of the substantially longer second electrode pair  2  ( 520 ), the fluid  502  loses substantially all of the charged particles (e.g.,  22  of  FIG. 2 ), during which time the second current measurement I 2  of the fluid is provided. Accordingly, the length L 2  of the second electrode pair  520  is sufficient to allow substantially all of the charged particles to be polarized or plated out of the fluid  502  onto the drum  501  configured as the positive plate  520   a  of the second electrode pair  520 . Accordingly, if a high field voltage V is applied by voltage supply  540 , to the second electrode pair  2  ( 520 ), a current flow and corresponding conductivity resembling the waveform  450  of  FIG. 6B  could (potentially) be viewed in a given sample of the fluid  502  moving along the length of the second electrode pair ( 520 ). 
   Thus, by the time the fluid  502  flows between the first and second plates  530   a / 530   b  of the third electrode pair  530 , substantially all of the charged particles (e.g.,  22  of  FIG. 2 ) have been removed from the fluid, and the third current measurement I 3  of the fluid is provided. Accordingly, if a high field voltage V is applied by voltage supply  540  to the third electrode pair  530 , a “DC conductivity” (e.g.,  480  of  FIG. 6 ) may be determined based on the third current measurement I 3  of the third electrode pair  3  ( 530 ). Because substantially all of the charged particles (e.g.,  22  of  FIG. 2 ) have been removed from the fluid  502  and plated onto the drum  501  as the fluid flowed between the polarized plates of the respective first, second, and third electrode pairs  510 ,  520 , and  530 , a wiper  550  is utilized in the illustrated example to remove the charged particles from the drum  501  and to reintroduce them back into the fluid  502 . Thus, the wiper  550  and the rotation of the drum  501  serve to mix the charged particles back into the fluid  502 , such that the particle concentration of the fluid  502  at the first electrode pair  510  is substantially back to the original full concentration level. 
   Again, as in  FIG. 3 , by applying both a high and a low value DC voltage (e.g., Vhi and Vlo), for example, alternately across the electrode pairs of  FIG. 7 , two corresponding DC current values (e.g., I 1hi  and I 1lo , I 2hi  and I 2lo , and I 3hi  and I 3lo ) may be measured between the first and second plates  510   a / 510   b ,  520   a / 520   b , and  530   a / 530   b  of the respective electrode pairs  510 ,  520 , and  530 . 
   It will be appreciated that other such configurations and pumping means, such as a peristaltic pump, may be utilized to move the fluid between the plates of the electrode pairs  510 ,  520 , and  530 . In addition, the wiper  550  may be replaced by another particle removal means such as a turbulence inducing surface and/or a jet of fluid that blasts the charged particles from the drum  501 , for example. Further, the surface of the drum  501  or the second plates  510   b ,  520   b , and  530   b  may have various grooves or surface features that enhance or otherwise accommodate the movement of the fluid flow  506 , enhance current measurements, and/or improve characteristic determinations, for example. 
   Although the distance between the first and second plates of the three electrode pairs are illustrated as being the same, it will also be appreciated that the distances between the first and second plates of the three electrode pairs could be different. 
   Also, additional electrode pairs and current meters may be added to those illustrated. 
   In one implementation of the example of  FIG. 7 , the following parameters may be utilized: 
   The length L 1  of the first electrode pair  1  (e.g.,  510 ) is about 5 mm; 
   The length L 2  of the second electrode pair  2  (e.g.,  520 ) is about 50 mm; 
   The length L 3  of the third electrode pair  3  (e.g.,  530 ) is about 55 mm; 
   A width of all the electrodes (e.g.,  510 ,  520 , and  530 ), measured perpendicular to the flow direction (e.g.,  506 ) is about 50 mm. 
   The drum (e.g.,  501 ) or cylindrical common electrode has a diameter of about 100 mm and width of about 60 mm. 
   A gap between the second plates (e.g.,  510   b ,  520   b , and  530   b ) of the electrode pairs and the cylinder (e.g., drum  501 ) is about 1 mm. 
   A gap between the first electrode pair  1  (e.g.,  510 ) and the second electrode pair  2  (e.g.,  520 ), or between the second electrode pair  2  (e.g.,  520 ) and third electrode pair  3  (e.g.,  530 ) is about 1 mm. 
   A rotation rate of the cylinder (e.g., drum  501 ) is about 20 revolutions per minute. 
   A low voltage V Lo  applied on the first electrode pair  1  (e.g.,  510 ) is about 30 V. 
   A duration of the low voltage V Lo  pulse is about 2 sec. 
   A pause with zero voltage after the application of the low voltage V Lo  pulse is about 1 sec. 
   A high voltage V Hi  applied on any of the first, second, or third electrode pairs (e.g., 510, 520, and 530) is about 1,500V. 
   A duration of the high voltage V Hi  pulse is about 2 sec. 
   A pause with zero voltage after the application of the high voltage V Hi  pulse is about 1 sec. 
   Grounded guard electrodes (e.g., that are connected to ground potential through the current measuring devices) may be provided around the second plates of the electrode pairs, so that uncontrolled electrical current flow will have little to no effect on current measurements. 
   Accordingly, regardless of the measurement mechanism used, such as embodiment  100  of  FIG. 3  or embodiment  500  of  FIG. 7 , the current measurement data is analyzed, for example, by a computer or another such analyzer to determine one or more characteristics or parameters of the fluid. 
     FIGS. 8-11  illustrate an exemplary methodology  600  that facilitates monitoring and determining a conductivity of a flowing fluid based on current measurement data in accordance with one or more aspects of the disclosure herein, such as may be used in the conductivity and charge meter system  500  of  FIG. 7 , for example. 
   Although the methodology  600  is illustrated and described hereinafter as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events is not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects and/or embodiments of the description herein. Further, one or more of the acts may be carried out in one or more separate acts and/or phases. 
   With reference to  FIG. 8 , the method  600  begins at  602  where a fluid (e.g.,  502  of  FIG. 7 ) containing charged particles (e.g.,  22  of  FIGS. 1 and 2 ) is made to flow between first and second plates (e.g.,  510   a / 510   b ) of a first electrode pair (e.g.,  510 ). Then, at  610 , the fluid (e.g.,  502 ) flows between first and second plates (e.g.,  520   a / 520   b ) of a second electrode pair (e.g.,  520 ) located downstream of the first electrode pair (e.g.,  510 ), the fluid losing substantially all charged particles when flowing between the first and second plates (e.g.,  520   a / 520   b ) of the second electrode pair (e.g.,  520 ). 
   At  620 , a first current (e.g., I 1 ) of the first electrode pair (e.g.,  510 ) is measured. A second current (e.g., I 2 ) of the second electrode pair (e.g.,  520 ) is measured at  630 . 
   At  650 , the fluid characteristic (e.g., a conductivity of fluid  502 ) is determined based upon one or more of the currents (e.g., I 1 , and/or I 2 ) measured between the first and second plates (e.g.,  510   a / 510   b , and  520   a / 520   b ) of the respective first and second electrode pairs (e.g.,  510  and  520 ). 
   Thus, a high field conductivity σ Hi  (e.g.,  470  of  FIG. 6B ) may be determined from a measured first current (e.g., I 1 ) measured between the first and second plates (e.g.,  510   a / 510   b ) of the first electrode pair (e.g.,  510 ), for example, according to:
 
σ Hi   =I   1   /V   Hi   *d/ ( L   1   *D )
 
where
 
   I 1  denotes the current measured between the first and second plates of the first electrode pair, 
   V Hi  denotes a high voltage applied to the first electrode pair, 
   L 1  denotes a length of the first electrode pair in the direction of the fluid flow, 
   D denotes the width of the first electrode pair, and 
   d denotes the gap between the first and second plates of the first electrode pair. 
   Alternately, with reference to  FIG. 9 , after the fluid flows between the plates of the second electrode pair at  610  of the method  600 ,  615  comprises flowing the fluid (e.g.,  502 ) between first and second plates (e.g.,  530   a / 530   b ) of a third electrode pair (e.g.,  530 ) with the second electrode pair located between the first and third electrode pair (e.g.,  510  and  530 ), wherein substantially all of the charged particles (e.g.,  22  of  FIGS. 1 and 2 ) have been removed from the fluid (e.g., at  480  of  FIG. 6B ) when the fluid flows between the first and second plates (e.g.,  530   a / 530   b ) of the third electrode pair (e.g.,  530 ). 
   Further, with reference to  FIG. 10 , after substantially all of the charged particles have been removed from the fluid while flowing between the plates of the second electrode pair at  610  of the method  600 ,  616  comprises adding or reintroducing substantially all of the charged particles (e.g.,  22  of  FIGS. 1 and 2 ) back into the fluid (e.g., at  480  of  FIG. 6B ) upstream of the first electrode pair (e.g.,  510 ). For example, this may be accomplished with the aid of the wiper  550  illustrated in  FIG. 7 . 
   Finally, with reference to  FIG. 11 ,  601  of the method  600  comprises utilizing a rotating cylindrical drum (e.g.,  501 ) to facilitate the flowing of the fluid (e.g.,  502 ) and to implement the first plates (e.g.,  510   a ,  520   a ,  530   a ) of the respective electrode pairs (e.g.,  510 , and/or  520 , and/or  530 ). For example, as discussed above with respect to drum  501  of  FIG. 7 , the rotation of the drum  501  can provide a pumping action to force the fluid  502  between the electrode pairs to enable the current measurements, and can also be used to mix the particles back into the fluid  502  after removal from the drum  501  by the wiper  550 . 
   One or more other such characteristics may also be determined. 
   For example, a low field conductivity may be determined from the current measured from the first electrode pair according to:
 
σ Lo   =I   1   /V   Lo   *d /( L   1   *D )
 
where
 
   I 1  denotes the current measured between the first and second plates of the first electrode pair; 
   V Lo  denotes a low voltage applied to first electrode pair; 
   L 1  denotes a length of first electrode pair in the direction of the fluid flow; 
   D denotes a width of first electrode pair; and 
   d denotes a gap between the first and second plates of the first electrode pair. 
   In another example, a DC conductivity may be determined from a current measured from the third electrode pair according to:
 
σ dc   =I   3   /V   Hi   *d/ ( L   3   *D )
 
where
 
   I 3  denotes the current measured between the first and second plates of the third electrode pair; 
   V Hi  denotes a high voltage applied to third electrode pair; 
   L 3  denotes a length of third electrode pair in the direction of the flow; 
   D denotes a width of third electrode pair; and 
   d denotes a gap between the first and second plates of the third electrode pair. 
   In yet another example, a total charge of the fluid per unit volume may be determined from a current measured from respective first, second and third electrode pairs according to:
 
 Q   V =( I   1   +I   2   −[L   1   +L   2   ]/L   3   *I   3 )/( v*D*d )
 
where
 
   I 1  denotes the current between the first and second plates of the first electrode pair; 
   I 2  denotes the current between the first and second plates of the second electrode pair; 
   I 3  denotes the current between the first and second plates of the third electrode pair; 
   L 1  denotes a length of the first electrode pair in the direction of the flow; 
   L 2  denotes a length of the second electrode pair in the direction of the flow; 
   L 3  denotes a length of third electrode pair in the direction of the flow; 
   D denotes a width of the respective first, second and third electrode pairs; 
   d denotes a gap between the first and second plates of the first, second and third electrode pairs; and 
   v denotes a linear speed of the fluid flow. 
   In still another example, a particle conductivity may be determined from the current measured from the first electrode pair according to:
 
σ Part =σ Hi −σ Lo  
 
where
 
   σ Hi  denotes the high field conductivity, 
   σ Lo  denotes the low field conductivity. 
   In another example, a mobility of the charged particles may be determined according to:
 
μ=σ Part   /Q   V  
 
where
 
   σ Part  denotes the particle conductivity; 
   Q V  denotes total charge of the fluid (e.g.,  502 ) per unit volume. 
   In yet another example, a volume concentration of the charged particles may be determined according to:
 
 C   V   =k*Q   2   V /σ Part  
 
where
 
   Q V  denotes total charge of the fluid per unit volume, being determined from a current measured from the respective first, second and third electrode pairs; 
   σ Part  denotes the particle conductivity; 
   k is a proportionality factor that in the theoretical limits of uniform spherical particles can be calculated as:
 
 k= 1/(6*π*η* r )
 
   where
         η denotes a viscosity of the fluid;   r denotes a radius of the charged particles.       

   Although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and/or modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the disclosure. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and/or advantageous for any given or particular application. Furthermore, to the extent that the terms “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Also, the term “exemplary” as utilized herein simply means an example, rather than the best.