Abstract:
The static or dynamic weighing apparatus for weighing an object or item, comprising a weighing assembly that includes a base with four (4) load cells attached to it, two (2) active load cells and two (2) passive load cells. Each active load cell has a mounting side and a weighing side. They are mounted to the base and to each other via a rigid weighing platform and are rotated 180° with respect to each other in the horizontal plane, thereby generating respective inverse error signals when an object or item is placed on or passes over the weighing platform. The two (2) passive load cells are mounted in the same manner. A combination of the voltage outputs from each of the respective two (2) load cells pairs negates all horizontally and vertically induced errors thus yielding a highly accurate two (2) times normal weight signal of the object or item being weighed. Error voltages felt by the passive assembly, representing any present vertical vibration, is removed via electrical circuitry from the actual active weighing voltage output, resulting in a true weight of the object or item being weighed. The resulting output voltage over the designated time interval then represents the true weight of the object or item being weighed. A voltage-to-frequency converter is employed to transmit the corrected true frequency output due to the actual analog output voltage resulting from the active weight being measured to a binary counter over a pre-specified time period. By counting a pulse train that varies directly to the applied voltage over a specified period of time results in a natural averaging weight and the resulting count is the average and true count of the representative weight of the object or item being weighed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the weighing of items by employing a four (4) load cell configuration that permits for the optimum cancellation of all ambient environmental vibration in both the horizontal and vertical planes. The four load cell configuration is implemented in an apparatus where a tare weighing and a gross weighing are always performed for each and every item presented for weighing so to avoid all adverse temperature effects. The apparatus is used for both “static” and “dynamic” weighing. In a static configuration, the item is placed and removed from the weighing assembly using robotics, etc., while for a dynamic configuration the items are conveyed across the weighing assembly using some sort of conveyance mechanism. For static weighing, a minimum weighing rate of one (1) tare and gross weight reading per presentation per second is provided. For dynamic weighing, a rate of weighing of up to ten (10) tare and gross weight readings per second of twenty (20) weight readings per second in total are provided. 
   2. Description of the Prior Art 
   Heretofore, various mechanical and electrical systems have been proposed for correcting for environmental vibrations in weighing systems. Examples of analogous and non-analogous systems are disclosed in the following analogous and non-analogous U.S. Patents. 
                               U.S. Pat. No.   Patentee                   3,446,299   Lenowicz       3,731,754   Godwin, et al.       4,102,421   Ozaki, et al.       4,212,361   Stocker       4,593,778   Konishi, et al.       4,926,359   Konishi, et al.       5,117,929   Nakamura, et al.       6,013,879   Nakamura, et al.                    
U.S. Pat. No. 3,446,299 to Lenowicz, U.S. Pat. No. 3,731,754 to Godwin, U.S. Pat. No. 4,102,421 to Oazki, U.S. Pat. No. 4,926,359 to Konishi, U.S. Pat. No. 5,117,929 to Nakamura and U.S. Pat. No. 6,013,879 to Nakamura all teach some form of Analog to Digital conversion in a weighing apparatus. They all take one or more analog weight readings and perform an instantaneous conversion at a fixed point in time. The point in time selected might just happen to be a point in time when significant vibration is being experienced, thus resulting in inferior data.
 
   U.S. Pat. No. 3,446,299 to Lenowicz teaches a data clocking method somewhat similar to the data clocking method disclosed herein. 
   U.S. Pat. No. 3,731,754 to Godwin teaches a count that is output as a pulse train of fixed frequency. 
   As will be described in greater detail hereinafter, in the apparatus of the present invention a voltage-to-frequency (V/F) conversion is performed. Such voltage-to-frequency conversion functions substantially different from an analog-to-digital (A/D) conversion. Instead of purely converting an analog signal to a digital signal at a specified fixed point in time, the operation of a voltage-to-frequency converter is such that a continuous pulse train is always present. The frequency, or time period of the pulse, observed coming out of the V/F converter at a given point in time is the instantaneous reflection of the analog voltage at the input to the V/F converter at that very same given point in time. The represented output frequency is always linearly proportional to the input analog voltage level. Therefore, it becomes obvious, that as the input analog voltage fluctuates, the output frequency pulse train will fluctuate as well, in a linear manner. It follows that if a pulse train containing fluctuations in frequencies is accumulated over a fixed time interval, the final count represents an average of the analog voltage applied during that entire fixed time interval. Employed in this fashion, a V/F conversion over a fixed time interval, is an electronic natural means of averaging out noise present on an analog signal, be it Johnson Noise, or other random noise components, so long as they are significantly shorter in period than is the fixed time sampling interval. 
   Many benefits result from transmitting such a continuously varying digital pulse train. Being digital in nature the pulse train is not susceptible to undesirable electrical noise interference found in hostile environments like in a factory. Moreover, the data can be transmitted over great distances using coaxial cable, fiber-optics, etc. Then, at the receiving end, the data pulses need only to be accumulated over the desired fixed time interval in a counter. Therefore, unlike an A/D converter where numerous conversions may have to be performed and then averaged by the computing device, with V/F conversion, once the fixed time accumulation of pulses has expired, the computing device need merely read the counter. 
   U.S. Pat. No. 4,212,361 to Stocker, U.S. Pat. No. 4,593,778 to Kornishi, U.S. Pat. No. 4,926,359 to Kornishi, U.S. Pat. No. 5,117,929 to Nakamura and U.S. Pat. No. 6,013,879 to Nakamura all teach the use of a second or dummy load cell in a weighing apparatus. 
   U.S. Pat. No. 6,013,879 to Nakamura&#39;s shows sloping load output lines resulting from the use of two load cells. However this patent does not teach applying a load traversing rigid member connecting the two active cells or connecting two passive load cells. The rigid member serves two purposes. The main purpose is for the reduction of all horizontal vibration components based on the 180 degree out of phase mounting of the two respective load cells connected by the rigid member. The second purpose is for attaching a weighing surface to it, across which is conveyed a dynamic weighing. It is an expectation that the resulting sloping load cell output signals, the slope opposite for each respective load cell, are the result of the load being conveyed across the weighing surface, by physically starting immediately above one load cell and ending up immediately above the other load cell. In between are varying degrees of load exerted on the load cells when an object is somewhere in-between them. 
   As will be described in greater detail hereinafter in the weighing apparatus of the present invention, four load cells are employed. Each set of two load cells (serving as one assembly) are used to cancel-out horizontal vibration noise components. The additional set of two load cell assemblies further provide a mechanism for canceling-out vertical vibration noise components. 
   BRIEF SUMMARY OF THE INVENTION 
   An analog voltage-to-frequency conversion circuit is employed in addition to optical-isolation, for the purpose of transmitting acquired weight data over large distances. This methodology is selected in order to eliminate adverse environmental electrical noise interference as well as to avoid any potential ground loop problems. In addition, the use of an analog voltage-to-frequency conversion is to also average out random electrical system noise that is always present in electronic systems. The reconstruction of the original analog weight signal employed at the receiver module end using a frequency-to-analog voltage conversion circuit is for setting up and alignment and the adjustment for the proper pulse counting time interval in relation to the realization of stable weight data. The weight data output comprises sixteen (16) sourced output levels of optically isolated digital data bits that can be processed via either a PLC (programmable logic controller) or an industrial PC (personal computer). Circuitry is provided for detecting when a weight data reading should occur, whether by edge detection of the in-position presented item, a linear encoder from a servo motor, etc. for the purpose of triggering the counter that will accumulate the weight data pulses transmitted representative of the actual weight. 
   Though the preferred embodiment of this invention is used to weigh items by having them exert a normal weight force on a weighing platform (compression), this application is equally applicable for weighing suspended items (tension.) 
   Further, in the weighing apparatus of the present invention, a tare weight data reading is made after or before a gross weight data reading is made and subtracted from the gross weight reading so that all adverse weighing results due to a change in temperature are obviated. 
   When two identical load cells are mounted 180° out of phase with respect to one another on the same physical mounting base and connected via a common rigid member, it must follow that each load cell experiences the same applied horizontal forces in both the X and the Y-planes. Because both load cells are identical in make and model number per the manufacturer, both load cells need to respond similarly to any applied horizontal force. A horizontal force creates a small extraneous but undesirable output that is superimposed on the desirable load cell output from an applied normal force. Therefore, if an applied horizontal force in the X-plane creates a +δ (delta) change in output voltage in one load cell it must create a −δ change in the other load cell since it is rotated by 180° or out-of-phase with the first load cell. This is similarly applicable in the Y-plane. Therefore, the net change in output voltage from the two load cells after summing results in just the normal applied weight component, since all 6 changes due to any horizontally applied forces will theoretically cancel in both the X and Y-planes. 
   A load cell&#39;s output voltage resolution, though tiny in magnitude, is theoretically infinite, subject to the effect of Johnson Noise (thermal noise resulting from any resistive components.) Therefore, according to the teachings of the present invention the load cells employed in the weighing solution have a weighing capacity that significantly exceeds the capacity of the object or item being weighed. For instance, a one kilogram load cell might be employed to weigh a ten gram object or item; in this case only 1% of the load cell&#39;s capacity is being employed. Benefits clearly follow; deformation of the load cell is proportional to the applied load—if the full capacity deformation is 0.003 inches, it follows that the maximum deformation of the load cell is now only 0.000,03 inches. Also the voltage outputs due to the natural ringing frequency of the load cell, though still at the same frequency, are significantly reduced in amplitude requiring less filtering. Finally, the ringing frequencies can be kept significantly higher than by using a load cell for the stated capacity of the item to be weighed. 
   A further benefit from employing only a fraction of the capacity of a load cell is that any detrimental influences resulting from a load cell&#39;s hysteresis is minimized. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a perspective view of a weighing acquisition apparatus constructed according to the teachings of the present invention. 
       FIG. 1A  is an enlarged perspective view of one of the strain gauge type load cells used in the weighing apparatus shown in  FIG. 1 . 
       FIG. 2  is a schematic electrical circuit diagram for a transmitter module for the apparatus shown in  FIG. 1  constructed according to the teachings of the present invention. 
       FIG. 3  is a schematic electrical circuit diagram for a receiver module for the apparatus shown in  FIG. 1  constructed according to the teachings of the present invention. 
       FIG. 4  is a graph of voltage versus time and shows the voltages generated at nodes E 1  and E 2  in  FIG. 2  during the weighing of an object by the two, 180° out of phase, active load cells of the apparatus shown in  FIG. 1 . 
       FIG. 5  is a graph of voltage versus time and shows the voltage generated at a node J 1  by the summing of the voltages at E 1  and E 2  versus the voltage at E 2  during the weighings of one object by the two, 180° out of phase, active load cells of the apparatus shown in  FIG. 1 . 
       FIG. 6  is a graph of voltage versus time and shows the voltage generated at a Q output at node S of a One Shot shown in  FIG. 3  versus the voltage at node R at the output of a Frequency to Voltage Converter shown in  FIG. 3 . 
       FIG. 7  is an example of a graph of voltage versus time and shows the noise voltage generated at node J 2  when no object is present to be weighed versus the voltage at node L at the output of a differential amplifier which sums the voltages at nodes J 1  and J 2  shown in  FIG. 2 . 
       FIG. 8  is an example of a graph of voltage versus time and shows the noise voltage generated at node J 2  when an object is present to be weighed versus the voltage at node L at the output of a differential amplifier which sums the voltages at nodes J 1  and J 2  shown in  FIG. 2  when an object is present on the active load cells for weighing. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings in greater detail, there is illustrated in  FIG. 1  a very accurate, high speed weighing apparatus  10  constructed according to the teachings of the present invention. 
   The weighing apparatus comprises a base  12  mounting four load cells  14 ,  16 ,  18  and  20 . The first two cells  14  and  16  are active load cells and are rigidly connected together by an “active” weighing platform  22  which extends between the parallel spaced active load cells  14  and  16 . 
   The other two load cells  18  and  20  are “passive” load cells which are rigidly connected together by a rigid member  24 . A passive load  26  is mounted on the rigid member  24  by set screws for offsetting or countering the vibration noise induced weight of the weighing and the load thereon being weighed. 
   An in-feed rail  27  is positioned adjacent to one side of the weighing platform  22 . Objects  28  to be weighed are conveyed by a conveying mechanism, not shown, along the in-feed rail  27  to the weighing platform  22  and then exit the weighing platform  22  on a discharge rail  29 . The objects  28 , shown in  FIG. 1  are small glass vials each having a precise quantity of liquid therein. The conveying mechanism is not shown in  FIG. 1  so as not to complicate the illustration of the weighing apparatus  10  and the type of conveying mechanism used is not material to the weighing apparatus  10  or method. 
   The passive load  26  has a weight that approximates the weight of each of the objects  28  and the weighing platform  22 , which is situated immediately above rigid member  24 . 
   As shown, the passive load cells  18  and  20  are parallel spaced from and inline with the active load cells  14  and  16 . 
   As shown in  FIG. 1A , each of the load cells  14 – 20  has a mounting side  30  and a weighing side  32 . The load cells  14 – 20  are strain gauge type cells which are available from a number of manufacturers. In one embodiment of the weighing apparatus  10  of the present invention, Futech Model L2357 load cells were used. These load cells are made by Futech, Inc. of Irvine, Calif. 
   As shown, in  FIG. 1  the load cells  14  and  18  are in-line with each other and each load cell  14  and  18  has a cable  34  and  36 , respectively, each with four wire conductors therein connected to the strain gauge in each load cell  14  and  18  and extending from the mounting side  30 . 
   The other two strain gauge type load cells  16  and  20  have the opposite orientation to the orientation of the strain gauge type load cells  14  and  18  such that the mounting side  30  of the strain gauge type load cell  14  is opposite the weighing side  32  of the strain gauge type load cell  16  and has a cable  38  and  40  respectively connected thereto. Likewise, for the passive load cells  18  and  20 , the passive load cell  18  mounting side  30  is opposite the weighing side  32  of the passive load cell  20 . 
   The cable  36  goes to an instrumentation amplifier in the transmitter module shown in  FIG. 2 . The two load cells  14  and  16  are mounted 180° out-of-phase with respect to each other. This can be observed by the fact that the respective cables  34  and  38  exit load cells  14  and  16  in opposite directions as do the cables  36  and  40  from the load cells  18  and  20 . 
   An important feature of the present invention is the rigid connecting of the weighing platform  22  to the active load cells  14  and  16  and the rigid connection of the rigid member  24  to the passive load cells  18  and  20 . 
   The opposite orientation of the active load cells  14  and  16  and likewise of the passive load cells  18  and  20  is important to the teachings of the present invention since it provides inverse weighing signals from each pair of load cells  14  and  16  or  18  and  20 , resulting from the affects of horizontally induced vibration applied to both load cells. 
   As a result of the opposite orientations of the active load cells  14  and  16  and the opposite orientations of the passive load cells  18  and  20  and the rigid connecting of each pair of load cells  14  and  16  or  18  and  20 , vibrations and noise generated in the X, Y and Z planes is cancelled out by combining the signals generated by the four different load cells  14 – 20  as will be explained in greater detail hereinafter in connection with the description of  FIG. 2 . 
   Referring again to  FIG. 1 , two spaced apart photoelectric emitter/sensors  42  and  44  are mounted on mounting brackets  46  and  48  that are spaced outwardly from one side of the weighing platform  22  and discharge rail  29 . On the other side of the discharge rail  29 , weighing platform  22  and weighing apparatus  10  there are located reflecting mirrors  50  and  52  mounted on respective mounting brackets  54  and  56 . 
   The photoelectric sensor  42  senses the leading edge of an object or vial  28  over the weighing platform  22  and triggers a signal to a first one-shot-timer in the receiver module shown in  FIG. 3 , which then commences the counting of pulses for a representation of the item&#39;s gross weight. It is positioned so that it triggers the first one shot timer when an analog weight signal is stable, as shown in  FIG. 6 . 
   The photoelectric sensor  44  senses the leading edge of an object or vial  28  over the discharge rail  29  and triggers a signal to the first one-shot-timer in the receiver module shown in  FIG. 3 , which then commences the counting of pulses for a representation of the non-item&#39;s weight (tare or no load weight.) This photoelectric sensor  44  could also be positioned over the in-feed rail  27  instead of the discharge rail  29 . 
   The mirror or photo reflector  50  is paired with photoelectric sensor  42  used for the edge detection of an object or vial  28  for which a gross weight count is to be taken. 
   The mirror or photo reflector  52  paired with photoelectric sensor  44  used for the edge detection of an object or vial  28  for which a tare weight count is to be taken. It should be noted that an object or vial  28  has just been conveyed off the weighing platform  22  when such edge detection takes place, such that at this instance in time, no load of any type is on the weighing platform  22 . 
   Between the emitter/sensor  42  and mirror  50  are shown dotted lines  58  which indicate a transmitted light beam for edge detection of the objects or vials. 
   Between the mirror  52  and the emitter/sensor  44  are shown dotted lines  60  which indicate a reflection of the transmitted light beam  60  indicating that no item is breaking the light beam. 
   An arrow  62  indicates the direction of motion of the objects or vials  28 . 
   The photoelectric emitter/sensors  42  and  44  can be of any commercial type and in one embodiment of the weighing apparatus  10  of the present invention they were edge detectors made by Keyence of Woodcliff Lake, N.J., Keyence Model No. PZ-M Photoelectric sensor. 
   As shown in  FIG. 1  the photoelectric sensor  42  will have a leading edge detection as an object  28  is conveyed onto the weighing platform  22 . 
   Subsequently, the object will create a leading edge signal as it passes the light beam path from the photoelectric emitter/sensor  44  for a tare weight reading, i.e., so that a tare weighing signal can be generated when no object  28  is present on the weighing platform  22 . 
   Referring now to the circuit diagram shown in  FIG. 2 , the strain gauge type load cells  14  and  16  will generate inverse signals which are then amplified by an instrumentation amplifier  70  and then passed through a low pass filter  72 . 
   The load cells  14 – 20  are typically resistive foil strain-type load cells or they can be any other type of load cell. The load cells  14  and  16  are used to present the active weight load output and ambient environmental vibration outputs while load cells  18  and  20  are used to present only the ambient environmental vibration output. The load cells  14  and  16  are mounted 180° out-of-phase in the horizontal plane (shown in  FIG. 1 ) as are load cells  18  and  20 . This accomplishes noise cancellation in the horizontal plane while still providing an analog weight output for the normal force. By subtracting the resulting analog weight outputs found in the summed load cell outputs of load cells  18  and  20  from those of the summed load cell outputs of load cells  14  and  16 , in theory, only the resulting output signal representing the true weight measurement of the object or vial to be weighed results. In one preferred embodiment of the weighing apparatus  10 , load cell “compression” is used to measure normal positive forces. By reversing the differential input voltages to all load cells  14 – 20  (by switching the two sensing wires) the assembled weighing base can be literally inverted to operate in the “tension” mode for weighing suspended loads. 
   The instrumentation amplifiers  70  are used to amplify the tiny differential load cell output voltages into usable voltage signal levels for the electronics. 
   Each instrumentation amplifier  70  includes a resistive potentiometer  74  that is used to adjust for a constant differential output level to an applied reference weight load resting on each respective load cell. The purpose is not only to amplify the tiny differential voltages generated via any deformation of the load cell&#39;s internal Wheatstone Bridge, but also to equalize the voltage outputs that result from each load cell  14  and  16 . Each and every load cell  14 – 20  needs to generate the same relative output voltage for the same load placed on it. Load cell output is measured in mV/Volt. This output relationship is a physical property of a load cell and varies from one load cell to the next. 
   The low-pass filter  72  is used to eliminate all higher frequency vibrations that the load cell is physically subjected to. The larger the capacity of a load cell without weight loading (due to its typically larger mass), the higher is its natural ringing frequency. When a “singular” load cell bears a constant load, such as a weighing platform, the natural ringing frequency of the resulting “system” is reduced; the weighing platform acts as a fixed load. However, when two load cells are connected via a rigid member and attached to a common supporting base, the resulting natural frequency of the assembly now is increased again; a “new” load cell fixture has been created. Aside from the “new” load cell fixture&#39;s own natural ringing frequency when subjected to a “step-function” of applied load, there may also be ambient vibration noise that can introduce high-frequency components. Both “new” resulting load cell fixtures should be balanced for optimal vibration noise cancellation with respect to their resulting natural ringing frequencies. For the “active” load cell assembly we have load cells  14  and  16 , weighing platform  22  and object  28  shown in  FIG. 1 . For the “passive” load cell assembly we have load cells  18  and  20 , rigid member  24  and passive load  26 . 
   The output from the low pass filters  72  represented at nodes E 1  and E 2  and are passed, respectively, to an operational amplifier  76  each of which has an output H 1  or H 2 . 
   These outputs at nodes E 1  and E 2  are input, respectively, into the negative input of each operational amplifier  76 . A voltage adjustment is input into the direct input by a resistive potentiometer  78  which can be adjusted to provide an offset adjustment for the weight of the weighing platform  22 , the rigid member  24 , and the passive load  26 . The outputs H 1  and H 2  are supplied through resistors to a direct input of a summing operational amplifier  80  which has an output J 1 . The output J 1  is fed through a resistor to the direct input of a differential amplifier  82 . 
   At the same time, the passive load cells  18  and  20  which pick up vibrations in the vertical or Z plane produce voltage signals which are amplified by instrumentation amplifiers  70  and passed through low pass filters  72 , respectively to the negative input of one of two operational amplifiers  76 . A voltage adjustment is input into the direct input by a resistive potentiometer  78  which can be adjusted to provide an offset adjustment for the weight of the weighing platform  22 , the rigid member  24 , and the passive load  26 . The outputs H 3  and H 4  are supplied through resistors to a direct input of a summing operational amplifier  80  which has an output J 2 . The output J 2  is fed through a resistor to the negative input of the differential amplifier  82 . This differential amplifier  82  is fundamental to low frequency noise removal. 
   Nodes E 1 , E 2 , E 3  and E 4  are test points where filtered analog output voltages representative of all externally applied weight forces may be monitored. Of the four (4) load cells, two (2) load cells each make up two (2) respective weighing fixtures, the “active” load cells  14  and  16  and the “passive” load cells  18  and  20 . Analyzing the active fixture, as the load moves from one end of the weighing platform  22  to the other, the load exerted on each respective load cell will change with the position of the load. With the load positioned above or close to the end of the weighing platform  22  ( FIG. 1 ), the load cell immediately beneath it will realize a maximum load and produce the highest output voltage. The other load cell will realize a minimum load and produce the smallest output voltage. As a load is conveyed across the weigh platform  22  with a constant velocity, one load cell will produce a linear negative ramp in output voltage, while the other will produce a linear positive ramp in output voltage as shown in  FIG. 4 . Taken together and summed, the outputs produced by each load cell, when the amplifiers are adjusted correctly, will always yield a constant summed voltage outputs at test points J 1 , J 2  for a given representative load, regardless of where the weight load is located on the weighing platform  22 . 
   The unity gain inverting operational amplifiers  76  provide a means for negating the analog weight output voltages presented by the four low pass filters  72 . 
   The resistive potentiometers  78  are used to shift the output voltages from the operational amplifiers  76  to near zero volts as the result of adding fixed weight loads due to the rigid member  24  ( FIG. 1 ) and the weighing platform  22  and the passive weight load  26 . 
   Nodes H 1 , H 2 , H 3  and H 4  are test points that are used to monitor the adjustments of potentiometers  78 . 
   The two unity gain operational amplifier voltage followers  80  are used for summing the two (2) outputs at nodes H 1 , H 2  and H 3 , H 4 , respectively, from the operational amplifiers  76 . 
   Nodes J 1 , J 2  are test points for observing the combined conditioned signals resulting from load cells  14 – 20 , respectively. 
   The differential amplifier  82  subtracts ambient environmental noise vibration felt in the load cells  18  and  20  from similar ambient environmental noise vibration signals felt in the load cells  14  and  16  thus leaving only the active weight load response from load cells  14  and  16 . 
   Node L is a test point for observing only the resulting active load analog weight output signal. 
   The voltage at node L is supplied to a voltage-to-frequency converter  84  that generates an output pulse train  86  at node M with the instantaneous frequency directly proportional to the input analog voltage level. Since most voltage-to-frequency converters require a positive input voltage (no output of negative frequencies), the output voltage level J 1  fed to the direct input of differential amplifier  82  should be slightly more positive than the output voltage level J 2 , in the quiescent state with no applied active weight loads on the load cells  14  and  16 , fed to the positive input of differential amplifier  82 . This results in a required slightly (non-critical) positive voltage level at test point L. 
   Since a “gross” weight reading will always be accompanied by a “tare” weight reading, the difference in between these two weight readings represent the “net” weight. Should the input voltage into the voltage-to-frequency converter  84  be negative in nature at test point L, the resulting net weight data will contain a non-linearity error. 
   The output from the voltage-to-frequency converter  84  is fed to a transmission line driver  88  appropriate to the transmission medium employed to transmit the frequency pulses to a receiver module ( FIG. 3 ) as necessary, unless the receiver module is physically close to the transmitter module. The driver  88  could be for fiber optics, differential lines, coaxial, etc. 
   It will be understood that the summing of the signals from the four load cells  14 – 20  will result in a cancellation of noise and vibrations in the X, Y and Z planes thereby to provide a clean, weight indicating, output voltage signal at the output node L of the differential amplifier  82  which has been compensated for noise and vibrations in the X, Y and Z planes. 
   In  FIG. 3  is illustrated a block schematic circuit diagram for a receiver module which can be located close to or at a distance from the transmitting module represented in  FIG. 2 . As shown, the frequency  86  from the transmitting module is passed through an optical isolator  90  and from there is supplied to both a frequency-to-voltage converter  92  and to one input  93  of an AND gate  94 . The output of the frequency-to-voltage converter  92  has a node R where the reconstructed voltage signal can be tested. The voltage signal at the node R can be tested against past converted frequency counts for establishing valid weighing intervals of similar objects. 
   A weight request signal from a PLC or PC or the edge detecting photoelectric sensor/emitter  42  or  44  is supplied to a first one shot timer  96  having a resistive potentiometer  98  for adjusting the counting window time duration. This potentiometer  98  is adjusted to match the rates of weighing requirements for the object (product) presentation being processed. The clean output from this one shot timer  96  is supplied to another input  100  of the AND gate  94  and to a test node S which is a test point for measuring the time interval of the first one shot timer  96 . The time interval determines for how long the accumulation of frequency data pulses is permitted. It is also used to verify that a binary ripple counter  102  is connected to an output  104  of the AND gate  94 , and is accumulating frequency data pulses only when the available weight data signal is stable. 
   The edge detecting signal supplied to the first one shot timer  96  is also applied to a second one shot timer  106  having a Q-NOT output connected to a reset port of the binary ripple counter  102 . The binary ripple counter  102  can have a count from 0 to 65,000. 
   The optical isolator  90  is used when receiving frequency pulses over large distances. The primary purpose is to eliminate ground loops. Even for short distances it would be advisable to use the optical isolator  90 , if for no other reason than to isolate power supplies. 
   The frequency-to-voltage converter  92  is desirable though not required. It is an excellent tool to assure alignment of the weight envelope against the pulse counting interval established with the one shot timer  96 , when the receiver module is at a significant distance from the transmitter module. 
   The node R is a test point for viewing the reconstructed analog weight envelope. 
   The node S is a test point for measuring the time interval of the one shot timer  96 . The time interval determines for how long the accumulation of frequency data pulses is permitted. It is also used to verify that the binary ripple counter  102  is accumulating frequency data pulses only when the available weight data is stable. 
   The AND gate  94  will pass frequency pulses to the binary ripple counter  102  if and only if the one shot timer  96  enables the counting time interval. Frequency data pulses are otherwise always present at the input  93  of the AND gate  94 . 
   The binary ripple counter  102  counts the frequency data pulses representative of the weight load data and results in up to a sixteen (16) bit data count which can be processed by a PLC (programmable logic controller) or some other computing device like an industrial PC (personal computer.) The binary ripple counter  102  is reset when a request for the next weight data sample is issued by a PLC/industrial PC/or an edge detector sensing that an item is in position to be weighed. 
   The second one shot timer  106  generates a very short time pulse from the Q-NOT output for the purpose of resetting the count in the binary ripple counter  102  to zero. It is triggered by a request for weight data, whether it represents tare data or gross data. 
   The one shot timer  96  establishes the frequency count duration time interval when weight frequency data pulses can be accumulated in the binary ripple counter  102 . This time interval is provided with the Q output and controls the gating to the AND gate  94 . The time interval duration can further be adjusted or fine tuned via the resistive potentiometer  98  and this setting is a pure function of the rate of weight data acquisitions required per second for the respective product presentation. When the count duration time interval expires, the Q-NOT output is asserted to notify the PLC/industrial PC that the output levels of the binary ripple counter  102  is stable and valid. 
   Referring now to the graphic representation of the wave forms at different points in the transmitting circuit and the receiving circuit, the voltage at node E 1  is shown at  110  in  FIG. 4 . The voltage at node E 2  which is combined with the voltage at node E 1  is also shown in  FIG. 4  at  112 . 
   The combined signal, i.e., the voltage at H 2  and the voltage at H 1  which appears at the node J 1 , is shown at  114  in  FIG. 5  and is compared with the voltage at node H 2  shown at  112  in  FIG. 5 . 
   In  FIG. 6 , the voltage at node R is shown at  116 . The voltage pulse  118  in voltage waveform  116  has a non-stable leading edge and a non-stable trailing edge. The middle, stable voltage of this pulse  118  is compared with the Q output of the first one shot timer  96  which has a square wave shape as shown at  120  so that only the stable, middle portion of the voltage pulse  118  at the node R is used to obtain an accurate, clean measurement of the weighing of the object  28 . 
     FIG. 7  shows the comparison of a voltage waveform  122  from noise at node J 2  with the voltage at node L shown at  124  when there is no weight on the weighing platform  22 . A similar voltage waveform  122  is also present at node J 1 . 
   The voltage signal at node L when an object or item  28  is being weighed on the weighing platform is shown by the waveform  126  in  FIG. 8 . This waveform  126  is compared with the noise signal at the node J 2  when an object or item  28  is present on the weighing platform  22 , as shown at  128  in  FIG. 8 . A similar voltage waveform  128  would also be present in the active weight data at node J 1 . 
   From the foregoing description, it will be appreciated that the weighing apparatus  10  and method of the present invention described above have a number of advantages some of which have been described above and others of which are inherent in the invention. 
   Also, it will be understood that modifications can be made to the weighing apparatus and method of the present invention without departing from the teachings of the present invention. 
   Accordingly, the scope of the present invention is only to be limited as necessitated by the accompanying claims.