Fluid assembly and method for diagnostic instrument

A fluid assembly and a method are provided. In one embodiment, the fluid assembly is insertable into a container holding a first fluid to be supplied to a diagnostic instrument and comprises a first element, a second element, and a first conduit fluidly connected between the first element and the second element such that the first fluid in the container moves through the first conduit towards the diagnostic instrument. A second conduit containing a second fluid is fluidly connected between the first element and the second element. A pressure transducer is fluidly connected with the second conduit such that the second fluid is bounded within the second conduit by the first fluid and the pressure transducer. The pressure transducer monitors pressure of the second fluid to indicate a volume of the first fluid in the container.

BACKGROUND 
This case relates to a fluid assembly and a related method for use with a 
diagnostic instrument. 
A diagnostic instrument is a machine that can perform a test on a sample, 
such as blood and the like, to determine something in that sample. That 
something, such as the AIDS virus in the sample, may be medically 
significant. 
To perform such a test, the machine may mix the sample with a fluid, such 
as a reagent, a buffer, a diluent and the like. This fluid may be supplied 
in a fluid container, such as a bottle and the like. As the machine 
performs the test, the machine takes a needed amount of fluid from the 
fluid container. As the machine performs more and more tests, the fluid 
container is progressively emptied. 
However, given that the tests the machine performs are important, e.g. to 
determine whether a person is sick or not, it is desirable that the 
machine be substantially continuously ready to perform those tests. This 
means that the machine should have a substantially constant supply of 
fluid. Accordingly, there is a need to provide an assembly which can be 
used to inform a machine operator when a certain fluid container is close 
to being empty so that a new, "full" fluid container can be added, etc. 
SUMMARY 
A fluid assembly and a method are provided. In one embodiment, the fluid 
assembly is insertable into a container holding a first fluid to be 
supplied to a diagnostic instrument and comprises a first element, a 
second element, and a first conduit fluidly connected between the first 
element and the second element such that the first fluid in the container 
moves through the first conduit towards the diagnostic instrument. A 
second conduit containing a second fluid is fluidly connected between the 
first element and the second element. A pressure transducer is fluidly 
connected with the second conduit such that the second fluid is bounded 
within the second conduit by the first fluid and the pressure transducer. 
The pressure transducer monitors pressure of the second fluid to indicate 
a volume of the first fluid in the container. 
In one method, a first element is fluidly connected with a second element 
by a first conduit. The first element is fluidly connected with the second 
element with a second conduit containing a second fluid. A pressure 
transducer is fluidly connected with the second conduit. The first 
element, the second element, the first conduit and the second conduit are 
inserted into the container such that first fluid moves through the first 
conduit towards the diagnostic instrument. The second fluid is bounded in 
the second conduit by the first fluid and the pressure transducer. 
Pressure of the second fluid is monitored with the pressure transducer to 
indicate a volume of first fluid in the container.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
One embodiment of a fluid assembly 10 is shown in FIGS. 6 and 13. This 
fluid assembly 10 may be utilized in any suitable employment or with any 
appropriate piece of equipment. In one instance, the fluid assembly 10 may 
be used with an automated analyzer 58 (FIG. 13), such as those disclosed 
in U.S. patent application Ser. Nos. 08/715,924, 08/715,780, 08/716,079 
and 08/816,121. Those applications are assigned to the assignee of the 
present case and the disclosures thereof are incorporated herein in their 
entirety by this reference. The fluid assembly 10 may be utilized with an 
apparatus 60 (FIG. 13) which supplies a first fluid, which may comprise a 
concentrate supplied in a container 62 to be mixed with another or third 
fluid, such as water from a source 68, by a mixer 66, to at least one or 
more (1 through N), such as 4, automated analyzers 58 or other machines 
operatively associated with those analyzers 58. The fluid assembly 10 may 
supply such first fluid simultaneously to a plurality of analyzers 58. A 
control 64, such as a computer having a memory, such as a RAM, a ROM, a 
SFAM, an EPROM and the like, containing and running appropriate routines, 
may be operatively connected with the analyzer(s) 58 and the apparatus 60 
to intendedly monitor and govern operation of those devices. It is to be 
recognized that the fluid assembly 10 may be modified in any suitable 
manner to meet particular needs. Also, methods of operation, use, etc. 
associated with the fluid assembly 10 are described. It is to be noted 
that steps comprising those methods may be performed in any appropriate 
order. Further, steps from one method may be combined with steps from 
another method to arrive at yet additional methods. 
In an exemplary embodiment, the fluid assembly 10 comprises a first element 
or first manifold 12 illustrated in FIGS. 7 and 8. The first manifold 12 
includes a first body 14, a ledge 16 disposed on one end of the first body 
14, and a second body 18 located such that the ledge 16 is between the 
first body 14 and the second body 18. A notch 20 is disposed between the 
ledge 16 and one end of the second body 18. A first bore 22 extends from 
an end of the first body 14, opposite to the end of the first body 14 
adjacent the ledge 16, to an end of the second body 18, opposite to the 
end of the second body 18 adjacent the notch 20, A second bore 24 extends 
from an end of the second body 18, opposite to the end of the second body 
18 adjacent the notch 20, and exits the first body 14 at a location offset 
approximately 90 degrees from a position of the first bore 22 on the first 
body 14. 
In a particular embodiment, the first manifold 12 includes the following 
specifications. However, others are possible. For instance, the first 
manifold 12 may be substantially cylindrical in configuration. The first 
body may have an outer diameter of about 1.36 inches and extend about 0.64 
inches from an adjacent side of the ledge 16 which may be about 0.1 inches 
wide (axial length) and have an outer diameter of about 1.62 inches. The 
notch 20 nay be about 0.08 inches in axial length (width). The second body 
18 may extend from the notch 20 by a distance measuring about 0.38 inches 
and may have a sloping profile, measuring about 5 degrees, tapering from 
an outer diameter of approximately 1.09 inches to about 1.03 inches. An 
end of the first bore 22 on the first body 14 may have a diameter of about 
0.25 inches and a center of the first bore 22 may be offset from a 
centerpoint of the first body 14 by a distance measuring about 0.2 inches. 
An end of the second bore 24 on the first body 14, i.e. its centerpoint, 
may be located about 0.32 inches from the ledge 16 and have a diameter of 
about 0.339 inches. A centerpoint of an end of the second bore 24 located 
on the second body 18 may be offset by a distance of about 0.2 inches from 
a centerpoint of the second body 18. The first manifold 12 may be made of 
any suitable material, such as PVC (gray) and the like. 
The fluid assembly 10 also comprises a second element or ring 26, shown in 
FIGS. 9 and 10, which is movably engagable with the first manifold 12. The 
ring 26 includes a knurl 28 on its outer surface to facilitate application 
of force to the ring 26. The ring 26 includes threads 30 on its inner 
surface which are movably engagable with complimentary threads on a 
suitable first fluid container 62 (FIG. 13), such as a cubitainer 
available from Abbott Laboratories (Abbott Park, Ill.), containing a 
particular volume of first fluid, such as a concentrate and the like, to 
be supplied, possibly in a diluted or mixed form, by the fluid assembly 
10. The threads 30 may be replaced with any other structure which mates 
with a corresponding structure on the first fluid container 32. The ring 
26 also has an aperture 32 dimensioned for accepting the second body 18 of 
the first manifold 12. 
In a particular embodiment, the ring 26 may be substantially cylindrical in 
shape, may have an axial length of about 0.457 inches and a diameter of 
about 1.59 inches. The aperture 32 may have a diameter that measures about 
1.062 inches. 
The fluid assembly 10 further includes a third element or second manifold 
34, displayed in FIGS. 11 and 12. The second manifold 34 includes a first 
bore 36 and a second bore 38. Both of the bores 36 and 38 extend through 
the second manifold 34. A portion 40 of the first bore 36 adjacent a first 
fluid container 62 engaging surface 42 of the second manifold 34 is 
enlarged with respect to the first bore 36. A portion 44 of the second 
bore 38 adjacent the first fluid container 62 engaging surface 42 of the 
second manifold 34 is enlarged with respect to the second bore 38 such 
that the portion 44 is unbounded at at least one side. The portions 40 and 
44 and the first fluid container 62 engaging surface 42 facilitate 
efficient access of the fluid assembly 10 to first fluid within a first 
fluid container 62 (FIG. 13) into which the fluid assembly 10 is inserted 
while also reducing the likelihood that a portion of that first fluid 
container 62 might interfere with that first fluid access. 
In a particular embodiment, the second manifold 34 may have a substantially 
cylindrical shape, a thickness of about 0.5 inches and a diameter of about 
1.188 inches. A centerline of the first bore 36 is offset from a 
centerpoint of the second manifold 34 by a distance of about 0.3 inches 
and a centerline of the second bore 38 is offset from a centerpoint of the 
second manifold 34 by a distance of about 0.365 inches. Terminal ends of 
the first and second bores 36 and 38 are offset from the container 
engaging surface 42 by a distance of about 0.125 inches. 
To facilitate understanding of the fluid assembly 10, construction of an 
exemplary embodiment of the fluid assembly 10 is discussed. However, other 
constructions are possible. 
Referring to FIG. 1, the first manifold 12 and the ring 26 are positioned 
with respect to each other such that the second body 18 is aligned with 
the aperture 32 in the ring 26. The first manifold 12 and the ring 26 are 
moved with respect to each other such that the second body 18 is 
positioned inside the aperture 32. This movement continues until the 
aperture 32 resides in the notch 20 between the second body 18 and the 
ledge 16. The ring 26 is free to rotate within the notch 20 about the 
second body 18 responsive to force applied to the knurl 28 on the ring 26. 
As shown in FIG. 2, a first conduit 46, which may be an 8.5.times.0.25 inch 
piece of pipe, is fluidly connected with an end of the second bore 24 
opposite to the end thereof adjacent the second body 18. An end of the 
first conduit 46, opposite to an end thereof fluidly connected with the 
second bore 24, may be fluidly connected with the piece of equipment, such 
as the analyzer 58, the mixer 66, or both (FIG. 13), to be supplied with 
first fluid from the first fluid container 62 to be connected with the 
fluid assembly 10. 
An end of a second conduit 48 is fluidly connected with the end of the 
second bore 24 adjacent the second body 18. As FIG. 3 shows, an opposite 
end of the second conduit 48 is fluidly connected with an end of the 
second bore 38 in the second manifold 34 opposite to the end thereof 
adjacent the first fluid container 62 engaging surface 42. The second 
conduit 48 may be an 1/8 by 11 inch piece of threaded pipe, possibly made 
of 1/8 schedule 80 PVC, Type 1, Grade 1 (gray). Thus, a first fluid flow 
path is formed from the first fluid container 62, to the portion 44, 
through the second conduit 48, through the second bore 24 and through the 
first conduit 46 to a particular element, such as the analyzer 58, the 
mixer 66, or both (FIG. 13), being supplied with first fluid from the 
first fluid container 32. 
A third conduit 50, which may be a 12.times.1/8 inch piece of pipe (Pomalon 
thermoplastic fluoropolymer from Freelin-Wade, placed in an oven at 
approximately 65 degrees Celsius for about 10 minutes to straighten then 
cooled on a flat surface, for example) is fluidly connected between the 
first bore 22 in the first manifold 12 and the first bore 36 in the second 
manifold 34, as illustrated in FIG. 4. Then, as FIG. 5 displays, a 
pressure transducer or monitor 52 is operatively connected with and 
substantially fluidly seals at least one end of the first bore 22 in the 
first manifold 12 adjacent the first body 14. Other fluidic connections of 
the transducer 52 and a bounded volume of the second fluid are also 
possible. In a particular embodiment, the pressure transducer 52 may be a 
signal conditioned, temperature compensated and calibrated, silicon 
pressure sensor (0-1.45 psi, 0-85 degrees Celsius), such as Catalog No.: 
MPX5010GP available from Motorola. Connected in this fashion, the pressure 
transducer 52 monitors pressure within the first bore 22, the third 
conduit 50, the first bore 36 and the first fluid container 32. 
A housing 54 (FIG. 6) is added to the first manifold 12 along with 
electrical conductor connections 56, which electrically couple the 
pressure transducer 52 to a suitable control 64, such as a computer and 
the like having memory running suitable routines. The housing 54 may be 
substantially cylindrical in shape with a height of about 2.5 inches and 
an outside diameter of about 0.156 inches. The housing 54 may be made of 1 
1/4 schedule 40 PVC, Type 1, Grade 1 (gray). 
In one method of use of the fluid assembly 10, a first fluid container 62 
(FIG. 13) containing first fluid to be supplied is provided with an 
opening and a bottom. The fluid assembly 10 is inserted through the 
opening into an interior of the first fluid container 32. Specifically, 
the second manifold 34 is placed into the interior of the first fluid 
container 62 until the container engaging surface 42 engages or otherwise 
contacts a portion of the first fluid container 32. At the same time, the 
ring 26 engages a corresponding structure adjacent the opening of the 
first fluid container 62. 
Appropriate force is applied to the knurl 28 on the ring 26 such that the 
threads 30 on the ring 26 mate with complimentary structures, such as 
threads and the like, located at the opening of the first fluid container 
62. The threads 30 are advanced until the container engaging surface 42 
contacts a portion of the first fluid container 62. Such contact can 
provide an operator with feedback indicating intended installation of the 
fluid assembly 10 with respect to the first fluid container 62. If the 
first fluid container 62 were sufficiently flexible, the contact between 
the container engaging surface 42 and the portion of the first fluid 
container 62 may cause the portion of the first fluid container 62 to 
deflect, to flex, to deform or otherwise to move, thereby creating a 
substantially sloped profile of that portion of the first fluid container 
62. Such a sloped profile, in combination with the relevant configuration 
of the second manifold 34, i.e. the portions 40 and 44 and the container 
engaging surface 42, may reduce a "dead" volume of first fluid in the 
first fluid container 62, possibly reducing the dead volume to about 100 
.mu.l or about 2% of a volume of the first fluid container 62. Of course, 
other, possibly smaller dead volumes may be achieved possibly dependent 
upon a volume of the first fluid container 62, geometry of the first fluid 
container 62, etc. 
Also, as the fluid assembly 10 is installed with respect to the first fluid 
container 62, a suitable second fluid, such as ambient air and the like, 
is present in the conduits 46, 48 and 50. Importantly, suitable second 
fluid is located within the first bore 36, the third conduit 50 and the 
first bore 22 such that the pressure of that suitable second fluid can be 
monitored by the pressure transducer 52. Installation of the fluid 
assembly 10 with the first fluid container 62 causes a volume of suitable 
second fluid to be trapped and compressed within the first bore 36, the 
third conduit 50 and the first bore 22 by the first fluid present in the 
first fluid container 62. In other words, a volume of suitable second 
fluid within the first bore 36, the third conduit 50 and the first bore 22 
is bounded on one side by the first fluid and on an opposite side by the 
pressure transducer 52. In this fashion, the pressure of the suitable 
second fluid trapped in the first bore 36, the third conduit 50 and the 
first bore 22 is proportional to an amount of first fluid in the first 
fluid container 62. 
Assuming that the first fluid container 62 is "full" when the fluid 
assembly 10 is initially installed, an initial pressure reading taken by 
the pressure transducer 52. Given that the initial pressure reading 
represents a "full" first fluid container 62, and given the ability to 
substantially continuously monitor the pressure of the suitable second 
fluid trapped inside the first bore 36, the third conduit 50 and the first 
bore 22, the fluid assembly 10 can be used to monitor a level of first 
fluid within the first fluid container 62. Specifically, as first fluid is 
drawn from the first fluid container 62, through the portion 44, the 
second bore 38, the second conduit 48, the second bore 24 and the first 
conduit 46 to the particular piece of equipment, such as the analyzer 58, 
the mixer 66, or both (FIG. 13), supplied with the first fluid, the 
pressure of the suitable second fluid trapped in the first bore 36, the 
third conduit 50 and the first bore 22 changes. The change in trapped air 
pressure is indicative of the volume of first fluid removed from the first 
fluid container 62. Accordingly, if an initial volume of the first fluid 
container 62 were known, then, by substantially continuously monitoring 
the trapped air pressure, the volume of first fluid within the first fluid 
container 62 is also substantially continuously monitored. Illustrating 
further by example, a correlation between pressure monitored by the 
transducer 52, or more specifically a voltage presented by the transducer 
52, and volume of first fluid in the container 62 may be determined 
empirically. In one instance, it may be determined that the correlation 
is: 
0.10 Volts=1000 mL+/-11% 
Given this correlation, the following may be specified. 
______________________________________ 
VOLTAGE VOLUME 
______________________________________ 
0.210 V 100 mL 
0.400 V 2 L 
0.700 V 5 L 
1.200 V 10 l 
______________________________________ 
With the determined correlation and related specifics, the voltage 
presented by the transducer 52 can be sampled periodically, such as about 
100 times per second, to substantially continuously monitor volume of 
first fluid in the container 62. Of course, the voltage can be monitored 
at any desirable frequency and truly continuous monitoring can be provided 
by utilizing a suitable analog circuit. 
It is important to recognize that the first fluid level in the first fluid 
container 62 can be monitored substantially continuously by the fluid 
assembly 10 irrespective of size, configuration or construction of the 
first fluid container 62. Also, the pressure transducer 52 monitors 
pressure of the suitable second fluid within the first bore 36, the third 
conduit 50 and the first bore 22 without coming into contact with the 
first fluid in the first fluid container 62. This may be important in 
cases where the first fluid in the first fluid container 62 presents 
special considerations, such as difficulty of decontamination, cross over, 
etc. 
Once the first fluid level in the first fluid container 62 reaches a 
certain, predetermined value, as indicated by the pressure in the first 
bore 36, the third conduit 50 and the first bore 22 monitored by the 
pressure transducer 52, an operator may be signaled by the control 64 to 
replace the first fluid container 62 with another, "full" first fluid 
container 62. The ring 26 is removed from the first fluid container 62 by 
appropriate application of force to the knurl 28 and the fluid assembly 10 
is removed from the first fluid container 62. The fluid assembly 10 is 
then installed in a new "full" first fluid container 62 as described 
above. In some implementations of the fluid assembly 10, the connections 
56 to the pressure transducer 52 may be removed during installation of the 
fluid assembly 10 with the first fluid container 62. After installation is 
complete, the connections 56 may be replaced. 
To further illustrate utilization of the fluid assembly 10, the following 
example is provided. It is to be understood that other utilizations of the 
fluid assembly 10 are also possible. 
In the field of automated medical assay processing, various sample 
processing protocols may be used to determine patient results. Specific to 
some chemistries used in some of the sample processing protocols is the 
use of a buffer reagent that may be utilized to, e.g., rinse sample and 
reagent probes, wash magnetic particles, dilute samples, flush a relevant 
fluidics system, etc. Some medical assays can require relatively large 
amounts, such as greater than about 30 mL, in addition to daily 
maintenance flushes, of buffer reagent per patient test. This amount is 
magnified by the number of assays, sometimes about 800 per hour, 
performed. 
These relatively large amounts of buffer reagent may be rather expensive to 
provide, as shipping large volumes of fluid over large distances may be 
costly. Such expenses may contribute to rising costs in diagnostic health 
care for providers and patients alike. In an effort to address this, it is 
possible to provide, for example, a soluble concentrate form of the 
reagent buffer. In this case, the reagent buffer concentrate may be 
equivalent to the first fluid discussed earlier. 
The concentrate or first fluid may be provided to a user in need of mixing 
with a third fluid. In one exemplary embodiment, the first fluid may need 
a 9:1 third fluid (e.g. water)--concentrate dilution prior to use on-board 
an analyzer 58 or plurality of analyzers 58. The fluid assembly 10 and the 
mixer 66, along with other associated elements, such as valves, pumps, 
fluid conveying conduits and the like, utilized in performing the dilution 
may be provided in a substantially integrated fashion, such as automatic 
module or apparatus 60, shown by dotted lines in FIG. 13. 
To utilize the apparatus 60, a user makes a fluid connection to a source 68 
that supplies third fluid, such as purified water and the like. In a 
particular embodiment, the source 68 may provide about 1.53 L/min NCCLS II 
type water substantially within the range of about 5 to about 100 psig and 
at a temperature between about 5 and about 37 degrees Celsius. To make 
this connection, in an exemplary utilization, about 10 feet of 
approximately 3/8" ID tubing may be used with appropriate connectors 
compatible with the apparatus 60 and the source 68. 
With the fluid connection between the apparatus 60 and the source 68 being 
made, a user loads a container 62 containing first fluid (i.e. 
concentrate) onto the apparatus 60. Then, the user installs the fluid 
assembly 10 with the container 62 following the steps described above. 
Specifically, the fluid assembly is inserted into the container 62, the 
threads 30 are screwed onto a mating portion of the container 62, and the 
fluid assembly 10 is connected both fluidly, by first conduit 46, and 
electrically, by connections 56, to the apparatus 60. In this manner, the 
apparatus 60 provides both first fluid (concentrate) delivery and first 
fluid, concentrate and diluted, inventory monitoring functions. In some 
embodiments, the apparatus 60 may be provided with a pressurized drain 
and/or gravity drain ports which can fluidly connect relevant portions of 
the apparatus 60 to a suitable drain. Then, a series of tubing 72, 
possibly configured to form a manifold designed to balance first fluid 
diluted with third fluid flow to multiple analyzers 58, may be constructed 
and fluidly connected. 
In some embodiments, the apparatus 60 may be connected with the control 64 
by means of an RS232 port on the apparatus 60. This way, the control 64 
can determine when and how the apparatus 60 operates, i.e. turns on and 
off, etc. Illustrating by example, if any analyzer 58 needs first fluid 
diluted with third fluid, the control 64 allows delivery of that diluted 
fluid to begin by opening suitable valve(s), not shown for clarity, which 
are fluidly connected in series with relevant portions of the apparatus 
60. After a desired fluid flow path among the apparatus 60 and the tubing 
72 is opened, the control 64 can send a command signal for the apparatus 
60 to turn on and commence operation, that is diluting first fluid with 
third fluid. If all analyzers 58 were determined to be full (a tank for 
diluted first fluid contained on the analyzer 58 is full), the control 64 
can send a command signal to turn the apparatus 60 off and cease dilution 
of first fluid with third fluid and delivery of the diluted first fluid 
through the tubing 72. Electrical power is operatively connected to the 
apparatus 60 with an appropriate power cord provided. Incoming electrical 
power may be compatible with various worldwide requirements. In some 
embodiments, components on the apparatus 60 may be driven by about 36 V 
and about 5 V supplies. 
With appropriate connections being made, a user can operate the apparatus 
60. After receiving a suitable signal from the control 64 to turn on, 
incoming third fluid, e.g. water, from the source 68 is flushed to a drain 
for a predetermined time period, such as approximately three seconds, and 
is measured for resistivity by a sensor 74 fluidly connected with the 
mixer 66 (FIG. 14). Alternatively, another sensor, possibly fluidly 
associated with the source 68 or fluidly associated conduits, may be used 
to determine resistivity of the incoming third fluid. If resistivity 
measured by either sensor were greater than about 1 M Ohm, then the third 
fluid is routed to a pump, such as a positive displacement pump and the 
like, which delivers third fluid from the source 68 to the mixer 66. If 
measured resistivity is less than about 1 M Ohm, the flow of the third 
fluid is continued to be routed to drain and sampled, such as about every 
three seconds, for resistivity. If resistivity is not within an acceptable 
range after a certain, predetermined number, such as three, readings, a 
third fluid quality error may be conveyed to the user, such as by 
activating a corresponding indicator, such as a light emitting diode and 
the like, located at an appropriate location, such as on a keypad 
associated with the control 64 and/or the apparatus 60 or the like. 
Incoming third fluid may also be checked for adequate pressure, such as by 
sensor 76. Alternatively, another sensor, possibly fluidly associated with 
the source 68 or fluidly associated conduits, may be used to determine 
pressure of the incoming third fluid. In some cases, a third fluid 
pressure of less than about 5 psig may be determined to be inadequate. If 
incoming third fluid pressure is inadequate, then the apparatus 60 may be 
shutdown and an appropriate error, such as activating a low pressure 
indicator on the keypad, may be conveyed to the operator. 
Upon loading a new, full container 62 of first fluid, the user can instruct 
the apparatus 60 to perform a first fluid inventory level calibration. The 
transducer 52 on the fluid assembly 10 can deliver a baseline voltage to 
suitable software, running on the control 64 or on the apparatus 60, that 
correlates this baseline voltage with the container 62 being 100% full. 
The software monitors voltage changes and based on the voltage changes, 
reports information indicative of a first fluid level within the container 
62 to the user, such as via light emitting diodes or other indicators 
located on the keypad and the like. In a specific employment, when first 
fluid remaining in the container 62 is less than about 2 percent of the 
volume of the container 62, then the user may be notified and the 
apparatus 60 may discontinue operation until a new container 62 is loaded. 
In a particular embodiment, from the container 62, first fluid is routed to 
the pump that delivers first fluid to the mixer 66. Third fluid may be 
routed from the source 68 to a similar pump for delivering third fluid to 
the mixer 66. The first and third fluid pumps may be driven by a single 
motor operating at a substantially constant speed geared to drive the two 
pumps such that downstream first fluid to third fluid ratio is about 1 to 
about 9. 
In some instances, given characteristics of the first fluid (it may be a 
salt concentrate), the first fluid pump may be susceptible to salt build 
up. To deal with this, a portion of the third fluid may be routed to the 
first fluid pump for allowing substantially continuous flushing or 
cleaning of relevant first fluid pump surfaces. This portion of first 
fluid may generate a first fluid pump flush bi-product. The mixer 66 can 
accept not only the first and third fluids, but also the first fluid pump 
flush bi-product and provide mixing of those fluids to create a 
ready-to-use diluted first fluid. 
In some embodiments, the sensors 74 and 76 may be used to provide quality 
control for the mixing of the first fluid with the third fluid. If 
pressure monitored by sensor 76 were determined to be undesirable, such as 
greater than about 15 psig, to deliver to downstream analyzers 58, then 
the apparatus 60 may shutdown and provide feedback to the user, such as by 
activating an outgoing pressure indicator. If efficacy of the diluted 
first fluid is not within acceptable limits, such as having a conductivity 
substantially within the range of about 14.74 to about 17.76 mS/cm, then 
the diluted first fluid may be routed to drain. Conductivity of the 
diluted first fluid may be sampled periodically, such as about every three 
seconds, and may continue to be routed to drain for another time period, 
such as that corresponding to about three additional readings, prior to 
shutdown of the apparatus 60. If a shutdown occurs, a high or low 
conductivity indicator associated with the control 64 or the apparatus 60 
may be activated. 
If conductivity is within an acceptable range, then diluted first fluid may 
be routed to the tubing 72. The tubing 72 is connected to one or more 
analyzers 58. The control 64 accepts a signal from each analyzer 58 that 
indicates on-board diluted first fluid level. From this information, it is 
determined when the apparatus 60 turns on and off. This logic can provide 
continuous delivery of diluted first fluid to multiple analyzers 58 upon 
demand. 
In the above-described fashion, the apparatus 60 may reduce associated 
manual labor, may provide substantially continuous buffer capacity to the 
analyzers 58, may monitor first, third and/or mixed fluid quality, 
temperature, resistivity, conductivity, etc., can function with various 
fluid temperatures and pressures, and may have error self-diagnosing 
capability. 
In some embodiments, the apparatus 60 may include a drip pan integrated 
with a fluid flood detector fluidly associated with the first and third 
fluids to aid in fluid flood prevention. This fluid flood detector may 
comprise a pair of separated electrical conductors, a conductive path 
between which may be supplied by at least one of the first fluid, the 
third fluid, and the third fluid mixed with first fluid. Conductivity 
between those separated electrical conductors may be monitored to 
determine presence of at least one of the first fluid, the third fluid, 
and the third fluid mixed with first fluid to indicate a flood or leak or 
other unintended release of that fluid. 
A RS232 field service interface and customer keypad feedback may be 
provided with the apparatus 60 to diagnose errors. The apparatus 60 may 
also run an automatic decontamination mode.