Abstract:
The clinical analyzer includes a cuvette carrier that is moved in a manner to provide flexible assay timing and variable incubation periods. Multiple assays having such varied incubation times can be run concurrently in random-access, avoiding timing conflicts. Fluid delivery stations are placed around the cuvette carrier in positions that are independent of assay timing. The cuvettes move in unison, in multiples of incremental steps, along a closed geometrical path. The cuvette carrier is movable variable distances in opposite directions in a single time cycle to position specific cuvettes at specific locations for delivery of sample or reagent. The direction of movement of the cuvette carrier is preferably based on a determination of the shortest distance between the cuvette and respective fluid delivery stations. However, in each time cycle there is a net progressive incremental stepwise movement of the cuvettes in a selected direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to sample analysis systems for automated clinical analysis of biological fluid samples and more particularly to an apparatus and method that uses discrete reaction cuvettes and allows simultaneous performance of assays of varied predetermined incubation periods of samples and reagents. Preferably the cuvettes in the clinical analyzer traverse a closed path, such as a circular path of a cuvette ring. 
     2. Related Prior Art 
     In one known clinical analyzer, cuvettes for receiving sample and reagent are positioned one behind another in a straight line. The cuvettes are moved along a straight path or track, in a single direction, in movement cycles of fixed time duration. The movement cycles are often referred to as machine cycles or time cycles, (or just cycles, when clearly construed from the context), such as, for example, twenty seconds as used in a known clinical analyzer. 
     Each cuvette usually contains a discrete assay and each cuvette generally moves a fixed distance during each time cycle to a particular station to undergo a particular function, such as fluid delivery. 
     Fluid delivery is provided by separate fluid delivery stations that are usually located in a predetermined sequence alongside the straight track. As the cuvettes move progressively along their straight path of travel they pass each of the fluid delivery stations. Each cuvette receives a selected amount of sample, diluent, reagent, etc. from respective fluid delivery stations, depending upon the assay that is associated with each cuvette. 
     Another known clinical analyzer, as shown in European patent application 014064582, published Jan. 31, 1991, moves cuvettes along a circular path. The disclosed analyzer includes a circular reaction ring or cuvette ring that is rotatable about a central axis such that the cuvettes move along a circular path. Cuvette openings are spaced one next to another at a peripheral portion of the ring, which can accommodate, for example, 100 cuvettes. The cuvette ring rotates at fixed cyclic time intervals of, for example, 30 second duration. 
     Stations that perform fluid delivery or other functions, are usually provided near the periphery of the cuvette ring. 
     Whether a clinical analyzer moves cuvettes in a straight line path or along a circular path, or along any other non-linear path, of regular or irregular outline, the fluid delivery stations are usually provided at predetermined sequential locations along the travel path of the cuvette. Fluid delivery stations can also be combined with known robotically movable devices having selected ranges of movement. The collection of the events described in the succeeding paragraphs and the time durations and incubations between them is known as the assay protocol. 
     Each fluid delivery station may be specialized and set up to perform a specific fluid delivery function such as:
         1. dispensation of sample into a cuvette;   2. dispensation of diluent into a cuvette;   3. dispensation of reagent into a cuvette;   4. dispensation of an ancillary material into a cuvette.       

     Probes that aspirate and dispense liquids such as reagent can also be washed and re-used before each aspiration/dispensation cycle. Probes that aspirate and dispense sample are sometimes removed and replaced before each aspiration/dispensation cycle. 
     Cuvettes in a clinical analyzer may also be subjected to the following functions:
         1. transfer of a cuvette from its location in a track or cuvette ring to a luminometer;   2. light detection in a luminometer corresponding to a specific assay in a cuvette;   3. installation of a new cuvette in an open cuvette space in a track or cuvette ring if the cuvettes are not re-used;   4. washing of a cuvette after an assay is completed, if the cuvette is to be reused.       

     In order for a cuvette in a cuvette ring to receive fluid delivery or other function the cuvette ring rotates a predetermined amount during each time cycle, to move the cuvette step by step in each time cycle to a selected fluid delivery station or location. For example, the cuvette ring can rotate incrementally an amount equivalent to one cuvette space (the cycle distance) during each time cycle of movement. 
     Generally, the time it takes for a particular cuvette to reach a particular fluid delivery station or location is based on a predetermined incubation period of an earlier fluid delivery to the cuvette. The incubation time between sequential fluid deliveries is a multiple of the cycle duration and the number of time cycles it takes for a cuvette to move from one fluid delivery station to another fluid delivery station. The overall time period for an assay is the number of time cycles it takes for a cuvette to move from a first fluid delivery station to an assay read location where an assay reading can be made by a luminometer, for example. 
     Known clinical analyzers using a cuvette ring move the cuvettes in a predetermined fixed pattern every cycle, incrementing the ring position by a fixed number of positions every cycle to enable the introduction of a new test. This pattern may have multiple moves and stops to allow cuvettes to be positioned against the fluid delivery stations, wash station or read station, but the pattern repeats exactly every cycle. In one known clinical analyzer, the ring can have three different such patterns but within each such pattern the moves and stops are always the same. 
     It is well known that the physical layout of known clinical analyzers and the fluid delivery stations including the sequence and spacing of the fluid delivery stations and/or the location of robotically movable fluid delivery devices is generally based on a predetermined incubation period between consecutive fluid dispensations, such as sample dispensation and reagent dispensation. 
     Thus there is a tie between the incubation periods and the general physical layout of the fluid delivery systems in the known clinical analyzers. This tie severely limits or prevents the clinical analyzer from providing any variation in incubation time for different assays and as a result, the assay protocols are limited to having a few distinct values for the incubation durations. 
     I have found that I can break the tie between the physical layout of the fluid delivery system and assay timing by providing variable cuvette carrier motions in a fixed time cycle rather than be limited by non-variable movement of cuvettes along a circular path. Insofar as I am aware non-variable movement of cuvettes for a particular time cycle is prevalent in all known clinical analyzers that use a cuvette carrier. 
     I have discovered that by moving a cuvette in a cuvette ring from an initial selected reference location variable distances in selected directions to other selected locations for fluid delivery without waiting for fixed incremental ring movements in one direction, I can provide different incubation times between assay events that vary continuously, in multiples of the time cycle, within a wide range. This, in turn, provides the assay developers with much greater latitude in choosing the optimal incubation periods for each assay. Once the optimal incubation time periods are determined, the scheduling algorithms described in succeeding paragraphs will allow multiple assays of varying assay protocols to run in random-access. 
     By implementing variable movement of cuvettes in selected directions in a given time cycle I can also reduce the number of normally required fluid delivery stations from, for example, five to two. I can obtain this reduction in fluid delivery stations by moving different cuvettes, different distances at different incubation time intervals to two different fluid delivery stations (variable movement) for example, rather than have all cuvettes move at the same incubation time intervals in the same direction to each of five selected consecutive fluid delivery stations, for example. 
     In addition, I have found that with variable movement of cuvettes along a circular path in selected directions I can use priorities other than sequentially located fluid delivery stations to determine the physical layout of a clinical analyzer. For example I can conveniently locate fluid delivery stations based on conveniently available space and based on the ease of permitting access to the various fluid delivery and function stations in the clinical analyzer. In addition I can provide versatility in a fluid delivery station by enabling the same fluid delivery station to deliver one or more reagents and ancillary materials to a cuvette. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, 
         FIG. 1  is a simplified schematic drawing of a clinical analyzer incorporating the present invention; 
         FIG. 2  is a simplified schematic plan view of the cuvette ring thereof; 
         FIG. 2B  is a simplified schematic plan view of a magnetic ring; 
         FIG. 2C  is a simplified schematic side-view of the cuvette ring engaged to a portion of the magnetic ring; 
         FIG. 2D  is a simplified schematic side-view of the cuvette ring disengaged from a portion of the magnetic ring; 
         FIG. 3  is a simplified schematic plan view of the cover tray for the cuvette ring; 
         FIG. 4  is a simplified timing table for the clinical analyzer, detailing the events that occur in every time cycle; 
         FIGS. 5-19  are simplified schematic drawings of the movable cuvette ring relative to a fixed work surface at selected time cycles to show the activities being performed as indicated in the Table 3—Cycle Event Table. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A clinical analyzer incorporating one embodiment of the invention is generally indicated by the reference number  100  in  FIG. 1 . 
     The clinical analyzer  100  includes a cuvette ring or reaction ring  102  of known construction shown in simplified schematic form in  FIG. 2 . The cuvette ring  102  is movable in a horizontal plane about a central vertical axis. Movement of the cuvette ring  102  can be activated in a known manner by a suitable known stepping motor (not shown) with a known drive wheel (not shown) pressed against the outer circumference of the cuvette ring  102 . 
     The cuvette ring  102  ( FIG. 2 ) includes eighty cuvette openings, spaces, or positions equally spaced one next to another around a peripheral portion of the ring, with each cuvette opening accommodating a removable and preferably disposable cuvette  108 , shown in simplified form as a circle. 
     Equally spaced indicia lines with numbers at intervals of 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 80 along an inner border  22  of the movable cuvette ring  12  are intended to identify each of the eighty cuvettes and their corresponding cuvette spaces in the movable cuvette ring  102 . Thus each number or indicia line on the cuvette ring corresponds to a distinct cuvette number or cuvette position and will be referred to by a number 1-80. 
     The cuvette ring  102  is bordered by a surrounding fixed surface  200  of the clinical analyzer  100  ( FIG. 5 ). 
     For purposes of facilitating the description of this invention equally spaced cuvette reference indicia lines with numbers at intervals of  1   a ,  5   a ,  10   a ,  15   a ,  20   a ,  25   a ,  30   a ,  35   a ,  40   a ,  45   a ,  50   a ,  55   a ,  60   a ,  65   a ,  70   a ,  75   a , and  80   a  are provided on the fixed surface  200  ( FIG. 5 ) to correspond with and register with the indicia lines and numbers 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 80 that represent the cuvette openings and cuvettes on the cuvette ring  102 . All cuvette reference numbers and indicia lines on the fixed surface  200  indicate a distinct reference position and will be referred to in the description by a number 1-80 followed by the letter “a”. 
     Although the cuvette ring  102  has eighty cuvette openings for eighty cuvettes, the number of cuvette openings in the ring  102  is a matter of choice. 
     The cuvette ring  102  has a suitable cover tray  110  ( FIG. 3 ) which serves to protect the cuvettes  108  in the cuvette ring  102  from spillage or any other material that might otherwise fall into the cuvettes. 
     The cover tray  110  ( FIG. 3 ), which does not rotate with the underlying cuvette ring  102  ( FIG. 2 ), has two spaced port openings  114  and  116 . Sample is dispensed through the port opening  114  into selected cuvettes in the cuvette ring  102 , and reagent is dispensed through the port opening  116  into selected cuvettes in the cuvette ring  102 . Although not shown, when the cover tray  110  is placed over the cuvette ring  102  of  FIG. 5 , the port opening  114  aligns with the cuvette reference position  10   a  on the fixed surface  200 , and the port opening  116  aligns with the cuvette reference position  20   a  on the fixed surface  200 . 
     Thus sample is dispensed at only one location on the cover tray  110 , namely at the port opening  114 , and reagent is dispensed at only one location on the cover tray  110 , namely at the port opening  116 . By limiting the port openings in the cover tray  110  through which sample and reagent are dispensed, evaporation of sample and reagent is minimized and contamination of cuvette ingredients is minimized. 
     The cover tray  110  ( FIG. 3 ) also includes a port opening  120  through which new cuvettes are deposited into vacant cuvette spaces in the cuvette ring  102 . The port opening  120  is the only opening in the cover tray  110  through which new cuvettes can be deposited into vacant cuvette spaces. Although not shown, when the cover tray  110  is placed over the cuvette ring  102  of  FIG. 5 , the port opening  120  aligns with the cuvette reference position  31   a  ( FIG. 5 ) on the fixed surface  200 . 
     The cover tray  110  ( FIG. 3 ) further includes port openings  124 ,  126 ,  128 ,  130 ,  132 ,  134 ,  136  and  138 . The port openings  124 ,  126 , and  130  are for aspiration and dispense probes (not shown) used for a known wash operation, e.g. for immunoassays that use a solid phase capture such as magnetic particles. The port opening  132  is for an aspiration probe used in the wash operation. The port opening  128  is a wash dispense port and the port opening  134  is an acid injection port. The port  136  is a re-suspension port. The port  138  is a cuvette ejection port, wherein cuvettes pass upwardly through the cover tray  110  from the cuvette ring  102  for entry into a luminometer  140  in a known manner. 
     Although not shown, when the cover tray  110  is placed over the cuvette ring  102  of  FIG. 5 , the aspiration (wash) port opening  124  aligns with the cuvette reference position  69   a , the re-suspension port opening  126  aligns with the cuvette reference position  70   a , the wash dispense port opening  128  aligns with the cuvette reference position  71   a , the wash dispense port opening  130  aligns with cuvette reference position  75   a , the aspiration (wash) port opening  132  aligns with the cuvette reference position  76   a , the acid injection port opening  134  aligns with the cuvette reference position  77   a , the re-suspension port opening  136  aligns with the cuvette reference position  78   a , and the cuvette ejection port opening  138  aligns with the cuvette reference position  80   a.    
     Thus the reference positions  69   a  to  78   a  correspond to a wash station  188  ( FIG. 1 ) for performing a known wash operation. 
     The analyzer  100  ( FIG. 1 ) includes a sample pipettor robot  150  of known construction supported on an overhead rail  152  for movement along a horizontal plane and also in vertical directions. The sample pipettor robot  150  includes a disposable sample pipette or probe tip  156  that can descend and elevate relative to the sample dispense port opening  114  in the cover tray  110 . The sample pipettor robot  150  is movable on the rail  152  over a bin  158  that stores probe tips  156 . The sample pipettor robot  150  can access a selected disposable probe tip  156  in the bin  158  after a previously used probe tip  156  is detached from the sample pipettor robot  150 . The sample pipettor robot  150  then elevates with the new probe tip  156  and moves over a sample rack tray  162  to enable the probe tip  156  to access a selected sample tube  164  in the sample rack tray  162 . The sample pipettor robot  150  aspirates a predetermined amount of sample through the probe tip  156  from the selected sample tube  164  ( FIG. 1 ). 
     The sample pipettor robot  150 , with aspirated sample, descends to the sample dispense, port opening  114  in the cover tray  110  ( FIG. 3 ) to dispense sample through the probe tip  156  and the sample dispense port opening  114  to a selected underlying cuvette  108 , moved by the cuvette ring  102  ( FIG. 2 ) into alignment with the sample dispense port opening  114  in the cover tray  110 . After sample is dispensed into the selected cuvette  108 , the sample pipettor robot  150  moves over a tip disposal container  166  ( FIG. 1 ) for release of the disposable probe tip  156 . All movements of the sample pipettor robot  150  are carried out in a known manner. 
     The analyzer  100  also includes a reagent pipettor robot  170  ( FIG. 1 ) of known construction supported on the overhead rail  152  with the sample pipettor robot  150  or supported on a separate rail (not shown) spaced and parallel to the overhead rail  152 . The reagent pipettor robot  170  also moves back and forth, and forward and backward, as does the sample pipettor robot  150 , and includes a reagent pipette  172  that can descend and elevate relative to the reagent dispense port opening  116  in the cover tray  110  ( FIG. 3 ). 
     The reagent pipette  172  is preferably non-disposable and reusable. The reagent pipettor robot  170  is movable over a reagent tray  174  ( FIG. 1 ) to enable the reagent pipette  172  to enter a reagent access port  178  ( FIG. 1 ) of a selected reagent container (not shown) held within the reagent tray  174 . The reagent pipettor robot  170  aspirates a predetermined amount of reagent through the reagent pipette  172  from the reagent access port  178  and then moves to the reagent dispense port opening  116  ( FIG. 3 ) in the cover tray  110 . The reagent pipettor robot  170  then dispenses reagent through the reagent pipette  172  ( FIG. 1 ) and the reagent dispense port opening  116  ( FIG. 3 ) to a selected underlying cuvette  108  ( FIG. 5 ) that has been moved by the cuvette ring  102  into alignment with the reagent dispense port opening  116  in the cover tray  110  ( FIG. 3 ). 
     Once the reagent dispensation is completed, the reagent pipettor robot  170  is moved over a pipette wash station  180  ( FIG. 1 ) of known construction to enable the non-disposable reagent pipette  172  ( FIG. 1 ) to be washed in preparation for another reagent dispensing function. 
     The reagent pipettor robot  170  can also be used for dispensing ancillary material, e.g. a common reagent such as sample pretreatment material or diluent, from an ancillary tray  182  ( FIG. 1 ) after the reagent pipette  172  is washed. Thus, the reagent pipettor robot  170  can be positioned over the ancillary tray  182  for descent to an ancillary material access port  184  ( FIG. 1 ). The reagent pipettor robot  170  aspirates a predetermined amount of ancillary material from the access port  184  and then moves over to the reagent dispense port opening  116  ( FIG. 3 ) in the cover tray  110 . 
     The reagent pipettor robot  170  dispenses a selected amount of ancillary material through the reagent pipette  172  and the reagent dispense port opening  116  into a selected underlying cuvette  108  ( FIG. 2 ) that has been moved by the cuvette ring  102  into alignment with the reagent dispense port opening  116  ( FIG. 3 ) in the cover tray  110 . After reagent dispensation is completed, the non-disposable reagent pipette  172  is moved over the wash station  180  ( FIG. 1 ) for washing of the reagent pipette  172  in preparation for another aspiration and dispensation function of the reagent pipettor robot  170 . All movements of the reagent pipettor robot  170  are carried out in a known manner. 
     The clinical analyzer  100  further includes the luminometer  140  ( FIG. 1 ) of known construction for light detection of reactions in cuvettes  108  ( FIG. 2 ) that have completed their earlier assay operations including incubation with sample, reagent, ancillary material and wash functions. The luminometer  140  is located near the cuvette space  80  of the cuvette ring  102  of  FIG. 2 . Cuvettes  108  that are undergoing a light emitting reaction suitable for detection in the luminometer  140  provide analytical data that is used in the analysis or assay of different blood characteristics that are tested in each cuvette that receives sample and reagent. 
     At the appropriate time that a cuvette  108  ( FIG. 5 ) in the cuvette ring  102  is ready for assay reading in the luminometer  140  ( FIG. 1 ) the assay readable cuvette  108  will be in alignment with a known cuvette ejector or elevation device (not shown). The cuvette ejector device (not shown) pushes or otherwise transfers the assay readable cuvette  108  upwardly from the cuvette ring  102  into the luminometer  140 . A vacant cuvette opening is thus left in the cuvette ring  102 . The assay readable cuvette  108  that is received in the luminometer  140  remains inside the luminometer until the light detection or read operation is completed. In the clinical analyzer  100  the read operation includes dispensing a base material, generation of a light flash, reading the light emitted, and evacuation of the cuvette contents (not shown). After the read operation is completed, the cuvette  108  is ejected (not shown) from the luminometer  140  into a suitable disposal container (not shown). 
     The clinical analyzer  100  also includes a known wash station  188  ( FIG. 1 ) next to the luminometer  140 . The wash station  188  aligns the port openings  124 - 136  in the cover tray  110  ( FIG. 3 ) and prepares cuvettes, in a known manner, for entry into the luminometer  140 . Thus as cuvettes  108  ( FIG. 2 ) in the cuvette ring  102  move past the wash station  188  ( FIG. 1 ) they are operated on in a known manner by the wash station  188  to ensure that the reacting components in the cuvettes  108  emit the quantities and qualities of light that permit the luminometer  140  to adequately read the resulting light emissions and thus provide the data needed for each assay. 
     A cuvette loader  190  ( FIG. 1 ) of known construction deposits a new cuvette  108  into the vacant cuvette opening in the cuvette ring  102  ( FIG. 2 ) to replace a previously removed cuvette  108 . The cuvette loader  190  can also load the cuvette spaces of the cuvette ring  102  with cuvettes  108  for each new start-up operation of the clinical analyzer  100 . 
     In accordance with the present invention, the cuvette ring  102  has a preferred movement time cycle duration, such as twenty seconds. The movement time cycle duration is a matter of choice. A schematic illustration of the possible known functions that can be scheduled to occur during the twenty second time cycle is shown in the Timing Table of  FIG. 4 . 
     Referring to the Timing Table of  FIG. 4 , each individual second of the 20 second time cycle is indicated in the first column entitled Time/Second. 
     The second column in the Timing Table of  FIG. 4 , entitled Sample Pipettor indicates the specific time allocations within the twenty second time cycle for performance of various functions by the sample pipettor robot  150  ( FIG. 1 ). Thus the sample pipettor robot  150  operates in the first 10 seconds of the 20 second time cycle to pick up a pipette tip  156  ( FIG. 1 ) and aspirate sample in a known manner from a selected sample container in the sample tray  162 . 
     As further indicated in the Sample Pipettor column of  FIG. 4 , between the 10 th  the 11 th  second of the 20 second time cycle, the sample pipettor robot  150  dispenses aspirated sample, and between the 11 th  and the 13.5 second segment of the second time cycle the sample pipettor robot  150  ejects the sample pipette tip  156 . The sample pipettor robot  150  has no scheduled activity after 13.5 seconds of the 20 second time cycle. 
     The third column of the Timing Table of  FIG. 4  entitled Reagent Pipettor indicates the specific time allocations within the twenty second time cycle for performance of various functions by the reagent pipettor robot  170  ( FIG. 1 ). Thus the reagent pipettor robot  170  operates in the first six seconds of the 20 second time cycle to aspirate a first reagent R1 from the reagent tray  174  ( FIG. 1 ) followed immediately by aspiration of a second reagent R2 if needed. Both reagents R1 and R2 are simultaneously dispensed. However, if there is no need for consecutive aspiration of a second reagent R2, then the dispense operation will be limited to the reagent R1. 
     Thus between the 6 th  and 9 th  second of the 20 second time cycle the reagent pipettor robot  170  can simultaneously dispense whatever reagent R1 (and possibly R2) that was aspirated during the first six seconds of the time cycle. Between slightly less than nine seconds and slightly more than 11 seconds of the 20 second time cycle the reagent pipette  172  is washed at the wash station  180  ( FIG. 1 ) before the reagent pipettor robot  170  can begin another aspiration cycle. 
     As further indicated in the Reagent Pipettor column of  FIG. 4 , between the time period of slightly less than 12 seconds to slightly more than 15 seconds of the second time cycle the reagent pipettor robot  170  can aspirate another second reagent R2 if needed. Between slightly more than 15 seconds to slightly more than 17 seconds of the 20 second time cycle the reagent pipettor robot  170  can dispense the additional second reagent R2. The reagent pipette  172  is washed at the wash station  180  ( FIG. 1 ) in the time segment between slightly more than 17 seconds until slightly less than 20 seconds. 
     The fourth column of the Timing Table of  FIG. 4  entitled Wash and Acid Injection indicates the specific time within the 20 second time cycle that is allocated to the washing of cuvettes at the wash station  188  ( FIG. 1 ) before the assay readable cuvettes  108  ( FIG. 2 ) are ejected from the cuvette ring  102  into the luminometer  140  ( FIG. 1 ). An acid ingredient is also dispensed at the wash station  188  between the fourth and fifth seconds of the 20 second time cycle ( FIG. 4 ). The wash and acid injection are known operations. 
     The fifth column of the Timing Table of  FIG. 4  entitled Reagent Rocker indicates the specific time allocated to the rocking or mixing of reagent containers. The reagent rocking occurs twice in the 20 second time cycle. The first rocking operation extends from less than 6 seconds of the 20 second time cycle to slightly more than 10 seconds. The second rocking operation extends from slightly more than 14 seconds to slightly less than 19 seconds. The rocking of reagents is a known operation to ensure even distribution of the ingredients in the reagent tray  174  ( FIG. 1 ). 
     The sixth column of the Timing Table of  FIG. 4  entitled Luminometer indicates the specific time periods allocated to the operations associated with the luminometer  140  ( FIG. 1 ). For example, for a fraction of a second between the 2 nd  and 3 rd  second of the 20 second time cycle, a cuvette  108  ( FIG. 2 ) that has completed the read operation in the luminometer  140  is ejected from the luminometer. In another fraction of a second between the time interval of slightly less than 3 seconds to slightly more than 3 seconds, an assay cuvette  108  on the cuvette ring  102  ( FIG. 2 ) that is ready for a light detection or read operation is elevated or ejected from the cuvette ring  102  into the luminometer  140  ( FIG. 1 ). Light measurement or light detection within the luminometer  140  that constitutes the read operation, occurs during the time period of slightly more than 7 seconds to slightly less than 18 seconds of the 20 second time cycle. 
     The seventh column of the Timing Table of  FIG. 4  entitled Add New Cuvette indicates that the new cuvette loading procedure occurs between the 18 th  and 19 th  seconds of the 20 second time cycle. 
     The eighth column of the Timing Table of  FIG. 4  entitled Ring Movement indicates by blank spaces, the portions of the 20 second time cycle when the cuvette ring  102  ( FIG. 2 ) is stationary. The stationary periods align with actions on the cuvettes, such as sample and reagent dispensation, cuvette ejection and installation, and wash operations, as indicated in the other columns of  FIG. 4  The cuvette ring  102  is stationary during the first 4 seconds of the time cycle to allow the performance of a wash operation. From the 4 th  second to slightly less than the 5 th  second, movement of the cuvette ring  102  permits relative indexing between a known magnetic ring segment  300  ( FIG. 2B, 2C, 2D ) and the cuvette ring  102 , in a known manner. 
     The magnetic ring segment  300  normally moves with the cuvette ring  102  ( FIG. 2C ) for slightly more than 19 seconds of the 20 second time cycle. Similar to the magnetic ring mechanism described in FIGS. 6 and 6A of U.S. Pat. No. 5,827,478, the mechanism includes a plunger  302 , and when the plunger  302  is in its up position, a detent pin  304  coupled to the magnet ring  300 , is placed in its detent position. When the detent pin  304  is in its detent position a detent spring  306  forces an end  304   b  of the detent pin  304  through a slot formed in a wall region  308  of the cuvette ring  102  as shown in  FIG. 2C . Thus, in the detent position, the detent pin  304  engages the cuvette ring  102  and locks or couples, the cuvette ring  102  to the magnet ring  300  thereby allowing the cuvette ring  102  to move with the magnet ring  300 , instead of allowing the cuvette ring  102  to move relative to the magnet ring  300 . During the period that begins after 4 seconds and ends at approximately 4.5 seconds ( FIG. 4 ) the magnetic ring segment  300  detaches from the cuvette ring  102  ( FIG. 2D ) to enable the magnetic ring  300  to index one cuvette space with respect to the cuvette ring  102 . For example, and as described in U.S. Pat. No. 5,827,478, and as shown in  FIG. 2D , the plunger  302  drives the detent pin  304  against the detent spring  306  until the detent pin  304  is pushed completely through the slot in the wall region  308  of the cuvette ring  102 . At this point, the cuvette ring  102  is de-coupled from the magnet ring  300  and can therefore move relative to the magnet ring  300 . After the indexing operation, the magnet ring  300  again engages with the cuvette ring  102  ( FIG. 2C ) for movement with the cuvette ring  102 . This operation of magnetic ring  300  engagement/disengagement from the cuvette ring  102  is a known operation and the mechanism for enabling this magnetic ring detachment and re-engagement with the cuvette ring is a known mechanism. For example, U.S. Pat. No. 5,827,478, describes a cuvette ring movably coupled to a magnetic ring, where the magnetic ring and cuvette ring have circular shapes. 
     As further indicated in the Ring Movement column of the Timing Table of  FIG. 4 , the cuvette ring  102  ( FIG. 2 ) is stationary for a fraction of a second between the 4 th  and 5 th  seconds for acid dispense. The cuvette ring  102  then moves from approximately the 5 th  second to slightly less than the 6 th  second to bring a cuvette to a reagent dispensation position. The cuvette ring  102  then stops from the 5.5 second point to slightly less than 9 seconds to enable reagent dispensation. The cuvette ring  102  then moves for slightly less than 1 second to bring a cuvette to a sample dispensation location. 
     Sample is dispensed from slightly less than 10 seconds up to approximately 11.5 seconds. The cuvette ring  102  then moves from approximately the 11.5 second point to slightly more than the 12 th  second to bring another cuvette to the reagent dispensation location. The cuvette ring  102  is stationary from slightly more than the 12 th  second up to approximately 17.5 seconds for the second reagent dispensation. The cuvette ring  102  then moves for approximately 1 second to bring a cuvette to the cuvette loading position (if needed). The cuvette ring  102  stops for a fraction of a second between the 18 th  and 19 th  seconds to load a new cuvette in an open space on the carrier when it again moves for approximately half a second to bring a cuvette to the wash station. 
     All of the processes and operations indicated in the Timing Table of  FIG. 4  are known processes. However I have recognized that variable movement of the cuvette ring  102  during a fixed time cycle can permit attainment of varying predetermined incubation periods which is a fundamental feature of this invention. The timing and scheduling of such processes or operations to permit variable movement of the cuvette ring  102  during a fixed time cycle is also a fundamental feature of this invention. 
     Thus, variable rotational movement of the cuvette ring  102  during the fixed time cycle enables any assay being performed in a particular cuvette to be processed simultaneously along with other assays being performed in other cuvettes, all running with different incubation periods or different assay protocols. 
     Selecting the assay to be performed in each cuvette  108  ( FIG. 2 ) of the cuvette ring  102  is obtainable by scheduling the predetermined incubation period for each fluid dispensation in each cuvette, and controlling cuvette ring movement during each time cycle to permit timely fluid dispensations without conflicting with any of the other fluid dispensations, or any other operation of the clinical analyzer. 
     Thus, one of the keys to achieving predetermined incubation periods for each different assay is the scheduling of such assays such that no conflicts occur. Another key to achieving predetermined incubation periods for each cuvette is the programming of variable cuvette ring movement to coordinate with the operation of the various fluid dispensing mechanisms and other functional devices that provide a contribution to the clinical analysis of samples. 
     To illustrate the operation of the clinical analyzer with variable cuvette carrier movement, a series of simplified tests will be described including the manner of coordinating such tests so that they can be carried out without conflict. 
     Samples that are to be tested in the clinical analyzer are generally brought to an operator in random order without regard to the particular parameter that is being tested. For example, a sample may be subjected to one or more tests, and each test is carried out in an individual cuvette. A series of tests on a sample is known as a panel, such as a thyroid panel, an anemia panel or a routine physical examination blood panel. Each individual test or assay whether or not it is part of a panel of tests is carried out in an individual cuvette. 
     For example, the following Worklist of Table 1 has an agenda of seven tests to be performed. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Worklist 
               
             
          
           
               
                   
                 Sequence of Arrival 
                 Test Number 
               
               
                   
                   
               
               
                   
                 1 
                 Test 1 
               
               
                   
                 2 
                 Test 2 
               
               
                   
                 3 
                 Test 3 
               
               
                   
                 4 
                 Test 6 
               
               
                   
                 5 
                 Test 4 
               
               
                   
                 6 
                 Test 5 
               
               
                   
                 7 
                 Test 7 
               
               
                   
                   
               
             
          
         
       
     
     The Table 1 Worklist agenda is compiled as each test order or test request is given or otherwise communicated to an operator of the clinical analyzer. The Sequence of Arrival column in the Table 1 Worklist indicates the sequential order of arrival of the tests at the clinical analyzer. The Test Number column in the Worklist Table 1 indicates the type of test that is being performed. 
     Letters, numbers or a combination of letters and numbers or any other suitable identification can be used to identify the type of test being performed. Thus Test 1 may be for Folate. Test 2 may be for Testosterone. Test 3 may be for B12. Test 4 may be part of a thyroid panel. Test 5 may be for digoxin. Test 6 may be for estradiol, and Test 7 may be a test for phenytoin. 
     For discussion purposes each of the test numbers 1-7 in the Table 1 Worklist will be the subject of a single test corresponding to a single cuvette. 
     The cuvette ring  102  ( FIG. 2 ) starts each time cycle at a reference position known as an increment position. At the end of the first stationary period for the ring as indicated in the table in  FIG. 4 , the ring indexes one position counterclockwise to a new increment position. Within the fixed 20 second time duration of each cycle the cuvette ring  102  may also move variable amounts away from the increment position to accomplish selected functions for selected cuvettes. If any other ring moves occur during the time cycle, they will be compensated for at the end of the cycle by a final move of the ring that will bring it back to the new increment position, also defined as the incremented position. Therefore, the increment position of a given time cycle is the incremented position of the previous time cycle. Thus, the increment position of the cuvette ring  102  changes each time cycle by advancing in a predetermined counter-clockwise direction by one cuvette in each time cycle. 
     Referring to  FIG. 5 , each of the 80 cuvettes or cuvette positions or spaces in the cuvette ring  102  are distinctly identified by a numbered position 1-80, for discussion purposes. The position of the cuvette ring  102  in  FIG. 5  corresponds to the test conditions at the end of a soon to be described cycle 1 of the clinical analyzer  100 . 
     The fixed surface  200  in  FIG. 5  includes eighty numbered reference positions that remain fixed and register with the eighty movable cuvette spaces on the cuvette ring  102 . The eighty numbered reference positions on the fixed surface  200 , which are also provided for discussion purposes, serve as reference indicators to facilitate visualization of the changes in position of the eighty cuvettes on the cuvette ring  102  during movement of the cuvette ring  102 . 
     The incremented conditions at the end of a first time cycle and before a second time cycle are indicated in  FIG. 5 , wherein the cuvette  25  in the cuvette ring  102  aligns with the fixed reference position  25   a  on the fixed surface  200 . The cuvette  25  is the first cuvette, of seven sequential tests, to receive sample. 
     The movement pattern of the cuvette ring  102 , following incremental movement, during any twenty second time cycle is entirely variable and can differ in each and every time cycle of movement of the clinical analyzer  100 . However the cuvette ring  102  will always return to its newly incremented position at the end of each time cycle. 
     For example, between the beginning and end of a second time cycle as indicated in  FIG. 6 , the cuvette ring  102  is indexed one cuvette position or one reference position on the fixed surface  200  from the incremented ring position of  FIG. 5 . Thus in  FIG. 6  the Test 1 cuvette (cuvette  25 ) of the cuvette ring  102  now aligns with the reference position  26   a  on the fixed surface  200  of the clinical analyzer  100 . 
     In each succeeding time cycle the cuvette ring  102  will index one reference position per time cycle. Such indexing may be followed by variable rotational movements of the cuvette ring  102  in selected distances and selected directions for the purpose of dispensing sample and reagent and the performance of other functions of the clinical analyzer. However after all variable movements are completed, the cuvette ring  102 , before the end of the fixed time cycle, will return to its incremented position. 
     Most assays in a clinical analyzer usually have three distinct incubation periods. One incubation period occurs in the time duration between sample dispensation and dispensation of a first reagent (R1). A second incubation period can occur between dispensation of a first reagent (R1) and dispensation of a second reagent (R2). A third incubation period can occur between dispensation of a second reagent (R2) and the read operation in the signal reading station, where, for example a luminometer is used as a signal reader. An overall incubation period is the total time of the first, second and third incubation periods between the dispensation of sample and the read operation. 
     Incubation times for each of the three incubation periods previously described are determined during assay development to achieve optimal clinical utility and are preprogrammed into the instrument. 
     In accordance with the invention, once an incubation time is determined, the incubation time is divided by the cuvette ring movement cycle time of 20 seconds to ascertain the number of time cycles of cuvette ring movement that must occur in correspondency with the incubation time. Thus the incubation time can be of any selected time duration that is a multiple in whole numbers of the time duration of the cuvette ring movement cycle time. 
     The following Table 2—Test Definition Timing Parameters (Tdef), indicates the predetermined timing parameters or incubation periods for each of the seven tests listed in the Table 1—Worklist. 
     
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Test Definitions - Timing Parameters (Tdef) 
               
             
          
           
               
                   
                 Test ID 
                 Sample 
                 R1 
                 R2 
                 Read 
                 Overall 
               
               
                   
                   
               
             
          
           
               
                   
                 Test 1 
                 0 
                 15 
                 20 
                 21 
                 56 
               
               
                   
                 Test 2 
                 0 
                 14 
                 23 
                 19 
                 56 
               
               
                   
                 Test 3 
                 0 
                 10 
                 10 
                 11 
                 31 
               
               
                   
                 Test 4 
                 0 
                 5 
                 8 
                 7 
                 20 
               
               
                   
                 Test 5 
                 0 
                 5 
                 13 
                 22 
                 40 
               
               
                   
                 Test 6 
                 0 
                 5 
                 7 
                 8 
                 20 
               
               
                   
                 Test 7 
                 0 
                 16 
                 8 
                 17 
                 41 
               
               
                   
                   
               
             
          
         
       
     
     Dispensation of sample into a cuvette for each test in the Table 2—Test Definitions—Timing Parameters is considered to occur at the beginning of the incubation period for that sample or at “0” time. 
     Dispensation of reagent R1 into a cuvette for each of the seven tests in Table 2 occurs after a dispensed sample has incubated for the predetermined number of time cycles indicated in the column R1 of Table 2. Such incubation may be necessary for temperature equilibration or if the sample was delivered with pretreatment agent. Dispensation of the reagent R2 for each of the seven tests of Table 2 occurs after the sample and the reagent R1 have incubated for the predetermined number of time cycles indicated in the column R2 of Table 2. 
     The read operation for each of the seven tests of Table 2 occurs after the sample, the reagent R1, and the reagent R2 have incubated for the predetermined number of time cycles indicated in the Read column of Table 2. Thus the overall predetermined incubation time or total number of time cycles for a particular assay to be completed in the clinical analyzer, from sample dispensation to read operation is indicated in the Overall column of Table 2. 
     Table 2 does not necessarily indicate the order in which the seven listed tests are to occur. The order in which each of the seven tests occurs is determined by a cycle event analysis as indicated in the following simplified Table 3—Cycle Event Table. 
     
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Cycle Event Table 
               
             
          
           
               
                 Time 
                   
                   
                   
                   
                 New 
                 Ring Position at 
               
               
                 Cycle 
                 Sample 
                 R1 
                 R2 
                 Read 
                 Cuvette 
                 Luminometer 
               
               
                   
               
             
          
           
               
                 1 
                 001 Test 1 
                   
                   
                   
                   
                 80 
               
               
                 2 
                 002 Test 3 
                   
                   
                   
                   
                 79 
               
               
                 3 
                 003 Test 2 
                   
                   
                   
                   
                 78 
               
               
                 4 
                 004 Test 6 
                   
                   
                   
                   
                 77 
               
               
                 5 
                 005 Test 4 
                   
                   
                   
                   
                 76 
               
               
                 6 
                 006 Test 5 
                   
                   
                   
                   
                 75 
               
               
                 7 
                 (dilution) 
                 Dil addition 
                   
                   
                   
                 74 
               
               
                 8 
                 007 Test 7 
                   
                   
                   
                   
                 73 
               
               
                 9 
                   
                 004 Test 6 
                   
                   
                   
                 72 
               
               
                 10 
                   
                 005 Test 4 
                   
                   
                   
                 71 
               
               
                 11 
                   
                 006 Test 5 
                   
                   
                   
                 70 
               
               
                 12 
                   
                 002 Test 3 
                   
                   
                   
                 69 
               
               
                 13 
                   
                   
                   
                   
                   
                 68 
               
               
                 14 
                   
                   
                   
                   
                   
                 67 
               
               
                 15 
                   
                   
                   
                   
                   
                 66 
               
               
                 16 
                   
                 001 Test 1 
                 004 Test 6 
                   
                   
                 65 
               
               
                 17 
                   
                 003 Test 2 
                   
                   
                   
                 64 
               
               
                 18 
                   
                   
                 005 Test 4 
                   
                   
                 63 
               
               
                 19 
                   
                   
                   
                   
                   
                 62 
               
               
                 20 
                   
                   
                   
                   
                   
                 61 
               
               
                 21 
                   
                   
                   
                   
                   
                 60 
               
               
                 22 
                   
                   
                 002 Test 3 
                   
                   
                 59 
               
               
                 23 
                   
                   
                   
                   
                   
                 58 
               
               
                 24 
                   
                 007 Test 7 
                 006 Test 5 
                 004 Test 6 
                 004 Test 6 
                 57 
               
               
                 25 
                   
                   
                   
                 005 Test 4 
                 005 Test 4 
                 56 
               
               
                 26 
                   
                   
                   
                   
                   
                 55 
               
               
                 27 
                   
                   
                   
                   
                   
                 54 
               
               
                 28 
                   
                   
                   
                   
                   
                 53 
               
               
                 29 
                   
                   
                   
                   
                   
                 52 
               
               
                 30 
                   
                   
                   
                   
                   
                 51 
               
               
                 31 
                   
                   
                   
                   
                   
                 50 
               
               
                 32 
                   
                   
                 007 Test 7 
                   
                   
                 49 
               
               
                 33 
                   
                   
                   
                 002 Test 3 
                 002 Test 3 
                 48 
               
               
                 34 
                   
                   
                   
                   
                   
                 47 
               
               
                 35 
                   
                   
                   
                   
                   
                 46 
               
               
                 36 
                   
                   
                 001 Test 1 
                   
                   
                 45 
               
               
                 37 
                   
                   
                   
                   
                   
                 44 
               
               
                 38 
                   
                   
                   
                   
                   
                 43 
               
               
                 39 
                   
                   
                   
                   
                   
                 42 
               
               
                 40 
                   
                   
                 003 Test 2 
                   
                   
                 41 
               
               
                 41 
                   
                   
                   
                   
                   
                 40 
               
               
                 42 
                   
                   
                   
                   
                   
                 39 
               
               
                 43 
                   
                   
                   
                   
                   
                 3 
               
               
                 44 
                   
                   
                   
                   
                   
                 37 
               
               
                 45 
                   
                   
                   
                   
                   
                 36 
               
               
                 46 
                   
                   
                   
                 006 Test 5 
                 006 Test 5 
                 35 
               
               
                 47 
                   
                   
                   
                   
                   
                 34 
               
               
                 48 
                   
                   
                   
                   
                   
                 33 
               
               
                 49 
                   
                   
                   
                 007 Test 7 
                 007 Test 7 
                 32 
               
               
                 50 
                   
                   
                   
                   
                   
                 31 
               
               
                 51 
                   
                   
                   
                   
                   
                 30 
               
               
                 52 
                   
                   
                   
                   
                   
                 29 
               
               
                 53 
                   
                   
                   
                   
                   
                 28 
               
               
                 54 
                   
                   
                   
                   
                   
                 27 
               
               
                 55 
                   
                   
                   
                   
                   
                 26 
               
               
                 56 
                   
                   
                   
                   
                   
                 25 
               
               
                 57 
                   
                   
                   
                 001 Test 1 
                 001 Test 1 
                 24 
               
               
                 58 
                   
                   
                   
                   
                   
                 23 
               
               
                 59 
                   
                   
                   
                 003 Test 2 
                 003 Test 2 
                 22 
               
               
                   
               
             
          
         
       
     
     The Table 3—Cycle Event Table schedules activities for each of the seven tests listed in the Table 2—Test Definitions—Timing Parameters, based on the timing parameters for each test that are indicated in Table 2. 
     The Table 3—Cycle Event Table schedules sample dispensation, reagent dispensation, read operation and other requisite operations such as sample dilution and cuvette replacement to ensure that no conflicts occur. 
     A conflict is defined as a scheduling of two operations to occur at the same time, but which, as a practical matter cannot occur at the same time because of time limitations indicated in the Timing Table of  FIG. 4 . Examples of conflicting operations are a scheduling of two sample dispensations at the same time, two reagent dispensations at the same time, two luminometer readings at the same time or two new cuvette installations at the same time. A program for producing the Table 3—Cycle Event Table or for scheduling the test activities such that no conflicts occur can be developed in any suitable known manner by persons having ordinary skill in the art. 
     The Table 3—Cycle Event Table is analogous to a reservation system for an airline, where seats that are initially available eventually become occupied. This seat availability and unavailability can be analogized to available time slots in the Table 3—Cycle Event Table. Because of variability and timing of the incubation periods for different tests, there is a possibility that a time slot in the Table 3—Cycle Event Table is already occupied. Therefore if a time slot for a particular test B is already occupied by an activity for another test A, then the test B must be “reseated” or rescheduled for time slots that are available for the complete activity of test B. 
     For example, in the worklist of Table 1, Test 2 immediately follows Test 1. However, Test 2 cannot be scheduled into the system immediately following Test 1 because they would conflict in Cycle 16 for the R1 delivery time slot. When Test 1 was scheduled, it reserved the R1 delivery slot in Cycle 16. If Test 2 was scheduled right after Test 1, it would have to receive an R1 delivery in Cycle 16 at the same time slot occupied by Test 1 which would create a conflict. Therefore, the next assay, Test 3, is scheduled right after Test 1 to avoid conflicts with Test 1, and Test 2 is scheduled right after Test 3. 
     One of the advantages of variable timing of the incubation periods is that samples which could have relatively short incubation periods might languish in clinical analysis systems having fixed incubation durations for all assays. With variable timing of incubation periods as disclosed herein samples with relatively short incubation can be run simultaneously with assays having longer incubation periods. A further advantage is that samples which are brought to the clinical analyzer during operation of the analyzer can be scheduled for processing in open time slots in the Table 3—Cycle Event Table, without interfering with tests that are already scheduled in the Table 3—Cycle Event Table. 
     Once the timing parameters of each of the seven tests of Table 2 have been scheduled without conflict, as on the Table 3—Cycle Event Table, the sequence of testing for Tests 1 through 7 can be determined. Thus based on the Table 3—Cycle Event Table it is determined that a conflict will occur if Tests 1-7 are run in the sequence of their test numbers. The Table 3—Cycle Event Table will show that a non-conflict testing sequence should be Test 1, Test 3, Test 2, Test 6, Test 4, Test 5 and Test 7. 
     After the non-conflict test sequence is established, a cuvette position in the cuvette ring  102  for each test can be determined as indicated in the following Ring Table (Table 4). 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Ring 
               
             
          
           
               
                 Time Cycle 
                   
                 Overall Number 
                 Cuvette Position 
               
               
                 Number 
                 Test Sequence 
                 of Time Cycles 
                 on Ring 
               
               
                   
               
               
                 1 
                 Test 1 
                 56 
                 25 
               
               
                 2 
                 Test 3 
                 31 
                 49 
               
               
                 3 
                 Test 2 
                 56 
                 23 
               
               
                 4 
                 Test 6 
                 20 
                 58 
               
               
                 5 
                 Test 4 
                 20 
                 57 
               
               
                 6 
                 Test 5 
                 40 
                 36 
               
               
                 8 
                 Test 7 
                 41 
                 33 
               
               
                   
               
             
          
         
       
     
     Cuvette location or position in the cuvette ring  102 , as indicated in Table 4, is based on the number of time cycles that must elapse before the overall number of incubation time cycles, as indicated in Table 2—Test Definitions—Timing Parameters are completed for each of the seven tests. 
     It is a known requirement of clinical analyzers employing ring movement of cuvettes and a read operation, that after the overall incubation periods are completed for each test, the fully incubated cuvette must be located in the cuvette ring at a position that registers with the read position. 
     Thus in the clinical analyzer  100  when the fully incubated cuvette arrives at and registers with the read position, namely the reference position  80   a , an elevator or ejection mechanism (not shown) ejects the fully incubated cuvette upwardly from the cuvette ring  102  into the luminometer  140  ( FIG. 1 ), which is accessible at the reference position  80   a  on the fixed surface  200 . 
     Since the luminometer read position is at the reference position  80   a  on the fixed surface  200 , the position of the cuvette ring  102  for a particular assay is determined by subtracting the overall number of time cycles for a particular test and the number of sequential cycles before sample dispensation from 80, then adding one as indicated in the following formula.
 
Ring position For a Particular Assay=80−(overall number of cycles for that assay+cycle sequence number)+2(if the resulting value is less than 1, multiples of 80 are added to bring the value within the range of 1 to 80)
 
     As indicated in Table 2—Test Definitions—Timing Parameters, the Test 1 cuvette has an overall incubation period of 56 time cycles before it enters the luminometer  140 . Thus since the luminometer  140  ( FIG. 1 ) is accessible at the reference position  80   a  ( FIG. 5 ) on the fixed surface  200  of the clinical analyzer  100 , the Test 1 cuvette must be 56 time cycles or 56 cuvette positions away from the luminometer reference position  80   a  on the fixed surface  200 , including the cuvette position itself. Therefore the Test 1 cuvette, after it receives sample must be at the reference position  25   a  ( FIG. 5 ) of the fixed surface  200  of the clinical analyzer  100 . 
     For purposes of facilitating the description of movement of the cuvette ring  102 , the cuvette ring  102  is oriented in  FIG. 5  such that the numbered cuvettes as indicated by the numerical indicia on the movable cuvette ring  102  register with the corresponding numbered reference positions as indicated by the numerical indicia on the fixed surface  200  of the clinical analyzer  100 . 
     It will be assumed that the position of the cuvette ring  102  in  FIG. 5  at the end of the first cycle is the incremented position for the first cycle. It will be noted that the test cuvettes  23 ,  25 ,  33 ,  36 ,  49 ,  57  and  58  are each distinctly identified in the cuvette ring  102  for  FIGS. 5-19 . However these cuvettes do not receive sample or reagent until the cycles specifically indicated in the Table 3—Cycle Event Table as will be described herein. 
     In order for the Test 1 cuvette (cuvette  25 ) to receive sample the cuvette ring  102  ( FIG. 5 ) must rotate to bring the Test 1 cuvette to the sample dispense port  114  ( FIG. 3 ) in the cover tray  110  to receive sample. The sample dispense port  114  corresponds to the reference position  10   a  ( FIG. 5 ) on the fixed surface  200 . After sample is dispensed into the Test 1 cuvette, the cuvette ring  102  rotates fifteen cuvette positions in a counterclockwise direction to return to its incremented position, which registers with the reference position  25   a  on the fixed surface  200 . 
     It should also be noted that the Test 1 cuvette  25  can be moved to the sample dispense reference position  10   a  ( FIG. 5 ) on the fixed surface  200  by rotating the cuvette ring  102  counterclockwise from the reference position  25   a  on the fixed surface  200  to the reference position  10   a  on the fixed surface  200 , which is a distance of sixty-five cuvette spaces. However the cuvette ring  102  is preferably programmed to rotate in a direction that results in the smallest ring movement to get to a particular destination, to save time. Thus the cuvette ring  102  will be programmed to rotate the Test 1 cuvette fifteen cuvette positions clockwise rather than sixty-five cuvette positions counterclockwise to reach the sample dispense port reference location  10   a  on the fixed surface  200 , to receive sample dispensation. 
     For purposes of clarity the cover tray  110  of  FIG. 3  is not shown in any of the  FIGS. 5-19 . However it should be noted that the sample dispense port opening  114  in the cover tray  110  of  FIG. 3  corresponds to the sample dispense reference position  10   a  on the fixed surface  200  of  FIGS. 5-19 . Also the reagent dispense port opening  116  of the cover tray  110  in  FIG. 3  corresponds to the reagent dispense reference position  20   a  on the fixed surface  200  of  FIGS. 5-19 . 
     As previously indicated, the cover tray  110  ( FIG. 3 ) does not rotate with the underlying cuvette ring  102  ( FIGS. 5-19 ). Therefore the sample dispense port opening  114  ( FIG. 3 ) and the reagent dispense port opening  116  in the cover tray  110  are always aligned with the sample dispense reference position  10   a  and the reagent dispense reference position  20   a  on the fixed surface  200  of  FIGS. 5-19 . Under this arrangement cuvettes in the cuvette ring  102  can only receive sample when a test cuvette in the cuvette ring  102  aligns with the sample dispense reference position  10   a  on the fixed surface  200  of the clinical analyzer as shown in  FIGS. 5-19 . 
     Furthermore, a test cuvette in the cuvette ring  102  can receive reagent through the reagent dispense port  116  ( FIG. 3 ) of the cover tray  110  only when the test cuvette in the cuvette ring  102  aligns with the reagent dispense reference position  20   a  on the fixed surface  200  of  FIGS. 5-19 . Cuvettes in the cuvette ring  102  that do not align with the sample dispense reference position  10   a  on the fixed surface  200  or the reagent dispense reference position  20   a  on the fixed surface  200  cannot receive sample or reagent. 
     Thus in order to receive sample or reagent, a cuvette in the cuvette ring  102  must register with the sample dispense reference position  10   a  on the fixed surface  200  of the clinical analyzer or the reagent dispense reference position  20   a  on the fixed surface  200  of the clinical analyzer. 
     As indicated in Table 2—Test Definitions, the cuvette for Test 3, which is the second sequential test in Table 3—Cycle Event Table, has an overall incubation time of thirty-one time cycles before it is subject to a read operation in the luminometer  140 . Therefore the Test 3 cuvette, after it receives sample, must be in a cuvette position that is thirty-one cuvette positions from the luminometer read reference position  80   a , including the cuvette position itself. 
     However sample dispensation can occur only once per time cycle because, as shown in the Cycle Timing of  FIG. 4 , sample dispensation takes up slightly more than eleven seconds of the twenty second cycle time. Thus, the Test 3 cuvette cannot receive sample during the same first cycle when sample is dispensed to the Test 1 cuvette. Therefore the Test 3 cuvette must receive sample during the next cycle, namely the second cycle. The Test 3 cuvette is thus positioned in the cuvette ring  102  at cuvette position  49  ( FIG. 6 ). 
     Under this arrangement the Test 3 cuvette (sequence 002 of Table 3—Cycle Event Table) is scheduled to arrive at reference position  50   a  on the fixed surface  200  of the clinical analyzer in the second time cycle wherein cuvette position  49  registers with the reference position  50   a  of the fixed surface  200 . 
     Thus during the second time cycle, sample is dispensed into the Test 3 cuvette which is located at cuvette position  49  ( FIG. 6 ). Sample is dispensed into the Test 3 cuvette during the time cycle when the Test 3 cuvette arrives at reference position  50   a , thirty-one time cycles or thirty-one cuvette positions away from the luminometer read station at reference position  80   a  on the fixed surface  200 , including the cuvette position itself. 
     At the end of cycle 1, cuvette position  49  registers against reference position  49   a  on the fixed surface  200 . At 4 seconds into cycle 2 the ring indexes to its incremented position to register cuvette  49  against reference position  50   a . In order for the Test 3 cuvette (cuvette  49 ) to receive sample the cuvette ring  102  ( FIG. 6 ) rotates clockwise from the reference position  50   a  on the fixed surface  200 , a distance of forty cuvette spaces to the sample dispense port reference position  10   a  on the fixed surface  200  where sample is dispensed into the Test 3 cuvette. The Test 3 cuvette is then rotated in a counterclockwise direction forty cuvette spaces by the cuvette ring  102  to return to its incremented position wherein the cuvette  49  on the cuvette ring  102  registers with the reference position  50   a  on the fixed surface  200 . 
     Since the Test 3 cuvette (cuvette  49 ) must move from the reference position  50   a  on the fixed surface  200  to the reference position  10   a  on the fixed surface  200  to receive sample dispensation, it is equidistant (forty cuvette spaces) from the sample dispense reference position  10   a  on the fixed surface  200 , whether the cuvette ring  102  rotates clockwise or counterclockwise. Therefore there is no preferred direction of shortest distance choice to dictate whether the cuvette ring  102  should rotate clockwise or counterclockwise to obtain sample dispensation to cuvette  49 . 
     The cuvette ring  102  can thus be programmed to move in a selected clockwise or counterclockwise direction to the sample dispense port reference position  10   a  when there is no preferred shortest distance direction to the sample dispense reference position  10   a.    
     As indicated in Table 2—Test Definitions the assay of Test 2 has an overall incubation time of fifty-six cycles. The assay of Test 2 is scheduled to occur third in sequence as indicated on the Table 3—Cycle Event Table. Therefore the Test 2 cuvette (sequence 003 of Table 3—Cycle Event Table) is positioned in the cuvette ring position  23  ( FIG. 7 ). The cuvette position  23  on the cuvette ring  102  ( FIG. 7 ) will register with the reference position  25   a  on the fixed surface  200  at the end of the third time cycle ( FIG. 7 ). 
     Under this arrangement the Test 2 cuvette (sequence 003 of Table 3—Cycle Event Table) is scheduled to arrive at reference position  25   a  on the fixed surface  200  during the third time cycle. The Test 2 cuvette at position  23  on the cuvette ring  102  is ready to receive sample during the time cycle when it is fifty-six counterclockwise cuvette spaces away from the luminometer read station at reference position  80   a  on the fixed surface  200 , including the cuvette position itself. 
     At the end of cycle 2, cuvette position  23  registers against reference position  24   a  on the fixed surface  200 . At 4 seconds into cycle 2 the ring indexes to its incremented position to register cuvette  23  against reference position  25   a . In order for the Test 2 cuvette (cuvette  23 ) to receive sample dispensation the cuvette ring  102  ( FIG. 7 ) rotates in a clockwise direction fifteen cuvette positions, to the sample dispense port reference position  10   a  on the fixed surface  200  to align cuvette  23  with the sample dispense reference position  10   a . The cuvette ring  102  then rotates the Test 2 cuvette (cuvette  23 )( FIG. 7 ) in a counterclockwise direction the same number of cuvette positions to return to its incremented position wherein cuvette  23  in the cuvette ring  102  is aligned with the reference position  25   a  on the fixed surface  200 . 
     The cuvette ring  102  can also theoretically rotate the cuvette  23  in a counter-clockwise direction a distance of sixty-five cuvette spaces to reach the sample dispense port reference position  10   a  on the fixed surface  200 . Since cuvette ring rotation is programmed to move in the direction of shortest distance to the sample dispense port reference position  10   a  on the fixed surface  200 , the cuvette ring  102  will rotate clockwise the fifteen cuvette positions to the sample dispense port reference position  10   a . It will also be noted that the cuvette  25  (Test 1)( FIG. 7 ) has incremented to the fixed surface reference position  27   a  and the cuvette  49  (Test 3) has incremented to the fixed surface reference position  51   a.    
     The fourth sequential assay as indicated on the Table 3—Cycle Event Table is the assay of Test 6 (sequence 004) which has an overall incubation period of twenty time cycles. However since the Test 6 cuvette (cuvette  58 ) must wait 4 cycles before it receives sample and thus progressively moves in four incremental steps four cuvette spaces until it receives sample, its position in the cuvette ring  102  is cuvette position  58  ( FIG. 8 ). As noted in  FIG. 8  the cuvette ring position  58  registers with the reference position  61   a  on the fixed surface  200  at the end of the 4 th  cycle and is therefore twenty cuvette spaces away from the luminometer including the cuvette position itself. In order to receive sample, the cuvette ring  102  needs to rotate twenty-nine positions counterclockwise to bring cuvette  58  to the sample dispensation port reference position  10   a  on the fixed surface  200 . After sample dispensation, the cuvette ring  102  is rotated clockwise twenty-nine positions to its incremented position for that cycle. 
     The cuvette  58  (Test 6) ( FIG. 8 ) can also receive sample by rotating the cuvette ring  102  clockwise fifty-one cuvette positions to the sample dispense port reference position  10   a  on the fixed surface  200 . Since the cuvette ring  102  is programmed to take the direction of shortest distance to the sample dispense port reference position  10   a  on the fixed surface  200 , the cuvette ring  102  will rotate counter-clockwise twenty-nine cuvette positions to the sample dispense port reference position  10   a . It will also be noted that the cuvette in the ring position  23  (Test 2) ( FIG. 8 ) has incremented to the reference position  26   a , the cuvette in the ring position  25  (Test 1) has incrementally moved to the reference position  28   a  and the cuvette in the ring position  49  (Test 3) has moved incrementally to the reference position  52   a.    
       FIG. 9  shows the position of the cuvette ring  102  corresponding to the end of the fifth cycle. Thus sample dispensation is made to the cuvette  57  (Test 4—sequence 005) during the time cycle when it has incrementally moved to the reference position  61   a  on the fixed surface  200 . 
       FIG. 10  corresponds to the position of the cuvette ring  102  at the end of sixth cycle. Thus sample dispensation is made to the cuvette  36  (Test 5—sequence 006) during the time cycle when cuvette  36  has incrementally moved to the reference position  41   a  on the fixed surface  200 . 
     As previously noted, each sample dispensation must always occur at the sample dispense port  114  ( FIG. 3 ) of the cuvette cover tray  110 , which sample dispense port  114  is at the reference position  10   a  on the fixed surface  200 . Thus the cuvette ring  102  must rotate a selected amount within a particular time cycle to move the particular cuvette needing sample dispensation to the sample dispense port reference position  10   a  and then return within the same time cycle to the original incremented position of the cuvette ring  102  for that same time cycle. 
     It is apparent from the description of sample dispensation for the Tests 1-6 that the cuvette ring  102  may rotate different amounts during any given time cycle to dispense sample at a time cycle that provides for incubation durations as detailed in the Table 2—Test Definitions Table and the Table 3—Cycle Event Table. 
     The Table 3—Cycle Event Table shows a dilution process in cycle  7 . A dilution consists of adding sample and diluent (from the ancillary tray  182  in  FIG. 1 ) into an empty cuvette in one time cycle. In the next time cycle, the diluted sample is aspirated from the dilution cuvette instead of from the sample tube  164  in  FIG. 1 , and then dispensed into a new cuvette as previously described. One of the advantages of this invention, due to the ability to perform variable ring movement, is that any cuvette on the cuvette carrier can be used for a dilution process rather than requiring that a cuvette be in a particular sequence. 
     To perform a dilution, sample is dispensed into an empty cuvette that is brought to the sample dispense port reference position  10   a  in a variable move from its current location. The cuvette is then moved to the reagent dispense port reference position  20   a  by a counterclockwise move of 10 positions to receive diluent by the reagent probe. In the next cycle, this cuvette is brought by a variable move from its current location to the sample dispense port reference position  10   a  to aspirate the diluted sample. Next, the cuvette of the target assay is brought to the sample dispense port reference position  10   a  for dispensing the diluted sample into it as previously described. The diluted sample is scheduled to receive reagents and undergo wash and read operations like a routine sample in accordance with the principles previously described. 
     As indicated in the Table 3—Cycle Event Table, sample dispensation for Test 7 takes place during the 8 th  time cycle ( FIG. 11 ). At the end of eighth time cycles the cuvette  33  (Test 7—sequence 007) in the cuvette ring  102  arrives, via incremental movement to the reference position  40   a  on the fixed surface  200  after having sample dispensed into it. 
       FIG. 12  shows the position of the cuvette ring  102  at the end of the 11 th  time cycle. As indicated in the Table 3—Cycle Event Table, on the 12 th  time cycle the Test 3 cuvette (cuvette  49 ) on the cuvette ring  102  is scheduled to receive a reagent R1. The Test 3 cuvette (cuvette  49 ) is at reference position  59   a  ( FIG. 12 ) on the fixed surface  200 . 
     During cycle  12  the cuvette  49  of Test 3 is incrementally moved to the reference position  60   a , where it is scheduled to receive reagent R1. Thus the cuvette ring  102  rotates 40 positions in either direction to the reagent dispense port at reference position  20   a  as shown in  FIG. 13 , to receive reagent R1. After the cuvette  49  of Test 3 receives reagent R1 the cuvette ring  102  rotates back to its incremented position in cycle  12 , before reagent dispensation, to once again align in cycle  12  with the reference position  60   a  as shown in  FIG. 14 . 
     All other cuvettes in the cuvette ring  102  ( FIG. 14 ) that have received sample are likewise incrementally moved an amount corresponding to the twelve incremental cuvette ring movements at the end of the 12 th  cycle. Thus the cuvette  23  of Test 2 is at the reference position  34   a , the cuvette  25  of Test 1 is at the reference position  36   a , the cuvette  33  of Test 7 is at the reference position  44   a , the cuvette  36  of Test 5 is at the reference position  47   a , the cuvette  57  of Test 4 is at the reference position  68   a  and the cuvette  58  of Test 6 is at the reference position  69   a.    
       FIG. 15  shows the cuvette ring  102  at the end of time cycle  23 . The cuvette  58  of Test 6 on the cuvette ring  102  is at the reference position  80   a  corresponding to the read position. The cuvette  58  of Test 6 is ready to be elevated or ejected into the luminometer  140  ( FIG. 1 ) for a read function at the beginning of cycle  24 . After removal, the cuvette ring  102  ( FIG. 15 ) is thus left with an empty cuvette space at the ring position  58 . The ring position  58  is therefore scheduled for installation of a new cuvette during cycle  24  as well, since the read time is early in the cycle and the cuvette installation time is late in the cycle, which allows cuvette replenishment to be carried out in the same cycle. 
     Referring to the Table 3—Cycle Event Table, four activities take place during the 24 th  cycle. Test 6 is read, reagent R1 is added to the cuvette of Test 7 (cuvette  33 ), reagent R2 is added to the cuvette of Test 5 (cuvette  36 ), and installation of a new cuvette occurs at position  58  of the ring. Also at the end of the 24 th  cycle the cuvette of Test 4 (cuvette  57 ) ready to be read in cycle  25 . 
     Thus during the 24 th  time cycle the cuvette ring  102  will exercise various movements from the end of the cycle  23  position shown in  FIG. 15 . First, cuvette  58  is elevated into the luminometer  140  for the read operation. The next movement is the regular indexing of the ring, which occurs after 4 seconds into the cycle, followed by a movement of the cuvette ring  102  to bring the cuvette  33  of Test 7 from the reference position  55   a  ( FIG. 15 ) to the reagent dispense port reference position  20   a  on the fixed surface  200 . Thus the cuvette ring  102  rotates clockwise thirty-five positions to the position shown in  FIG. 16 . 
     The next movement of the cuvette ring  162  during cycle  24  is to dispense reagent into the cuvette  36  of Test 5 which is at the reference position  23   a  ( FIG. 16 ) after reagent is dispensed to the cuvette  33  of Test 7. Thus the cuvette ring  102  moves three positions clockwise from the reference position  23   a  of  FIG. 16  to align with the reference position  20   a  of  FIG. 17  and permit reagent R2 to be dispensed into the cuvette  36 . 
     In the next movement of the cuvette ring  102 , the cuvette space  58  is moved by the cuvette ring  102  to the cuvette delivery station at the reference position  31   a  on the fixed surface  200  to receive a new cuvette as shown in  FIG. 18  from the cuvette loader  190  ( FIG. 1 ). 
     It should be noted that the cuvette loader  190  ( FIG. 1 ) can load a new cuvette into an open space in the cuvette ring  102  only when the open space on the cuvette ring  102  is aligned with the reference position  31   a  on the fixed surface  200  of the clinical analyzer as shown in  FIG. 18 . Thus any open space on the cuvette ring  102  must be brought to the reference position  31   a  on the fixed surface  200  of the clinical analyzer in order to receive a new cuvette. The new cuvette is transferred through the cuvette delivery port  120  ( FIG. 3 ) in the cover tray  110  to the open space  58  ( FIG. 18 ) on the cuvette ring  102  that aligns with the reference position  31   a  on the fixed surface  200 . 
     It is also feasible to use known cuvettes that are washed in a known manner at the clinical analyzer, and reused in the clinical analyzer. 
       FIG. 19  shows the position of the cuvette ring  102  at the end of the 24 th  cycle wherein the cuvette  57  of Test 4 is incremented one position from the position at the end of the 23 rd  time cycle ( FIG. 15 ). The cuvette  57  of Test 4 ( FIG. 19 ) aligns with the reference position  80   a  for assay reading wherein the cuvette  57  is ejected into the luminometer  140  at the beginning of the 25 th  time cycle. 
     The Table 3—Cycle Event Table for the 24 th  time cycle thus indicates four different activities. Each of the activities involves a movement of the cuvette ring  102  a variable amount during time cycle  24  to accomplish the required functions. At the end of the 24 th  time cycle ( FIG. 19 ) the cuvette ring  102  returns to its incremented position relative to the fixed surface  200 . 
     Thus before the end of each time cycle the cuvette ring  102  will always return to its incremented position after previously moving variable clockwise and counterclockwise amounts to accomplish the individual and plural functions scheduled for the cuvette ring in Cycle Event Table (Table 3). 
     The following principles summarize the Ring Positioning Logic, Ring Movement Logic and Conflict Management Logic. 
     New Cuvette Positioning Logic 
     In every cycle, there is a time slot where one of the cuvettes is moved to the read station (reference position  80   a ). The cuvette ring  102  increments by one position counterclockwise in every cycle. At the end of cycle 1, ring position  1  is at the work surface reference position  1   a . In cycle 2, ring position  80  is at work surface reference position  1   a , etc. The cuvette into which sample and reagents are introduced, must arrive at the read station reference position  80  after the number of cycles corresponding to the (“overall” value −1) for that test as defined in the Table 2—Test Definitions Table, so that reading will happen on the following cycle. Using the Table 3—Cycle Event Table, the formula for the cuvette positioning is: 
     Cuvette position=Ring size minus overall cycles for that test minus cycle number in Cycle Event Table where the test was introduced plus 2. If the resulting value is less than 1, multiples of the ring size are added to bring the value within the range of 1 to the ring size. For example, in Table 4—Ring, for Test 7 starting in cycle  8 , the position will be 80−41−8+2=33 
     Ring Movement Logic 
     The following is the logic flow for the calculations for the extent and direction of the next variable move:
         1. What is the present ring position?   2. What is the next action and which cuvette needs to have this action performed on it?   3. Identify the location where that cuvette needs to go.
           a) Move there, clockwise or counterclockwise.   b) Take the direction that furnishes the shortest path to the location where the cuvette needs to go.   
           4. The very last ring move in the time cycle is such that the net change of all the previous moves in that time cycle is one increment position in the chosen direction of incremental movement for the system
 
Conflict Management Logic
       

     The following is the logic flow for conflict management:
         1. For every new test (or skipped test due to a previous conflict), check that all corresponding Cycle Event Table spots are free.   2. Check if designated cuvette location on cuvette ring is free.   3. If yes to both 1 and 2, make all reservations.   4. If no, scan the Table 1—Worklist Table for all other samples.
           a) Apply logic steps 1 and 2 to every such sample.   b) If successful, make all reservations for the sample that meet criteria of logic steps 1 and 2. This will result in samples being out of original sequence.   c) If not, cycle is skipped and return to logic step 1.
 
It should be noted that the above stated logic is suitable to routine samples. Other considerations may alter it as required. For example, emergency samples may be preferentially scheduled ahead of other samples in life-threatening situations, or calibrators may need to be run ahead of routine samples.
   
               

     By using known principles of conflict management and known principles of programming the cuvette ring  102  is programmed to perform a discrete set of differing movements during each time cycle. The Table 3—Cycle Event Table for scheduling of activity during each time cycle to avoid conflicts is also established using known programming principles. 
     As various changes can be made in the above methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.