Flow meter

A device and method for determining the flow rate of gas entrapped fluids delivered in a pulsating flow, such as milk, wherein the invention boasts an improved fluid level detection arrangement for determining flow rates with improved accuracy, and an improved temperature sensing arrangement for determining the temperature of the gas entrapped fluid with improved accuracy.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
The present invention relates generally to devices for measuring flow 
rates. More particularly, the present invention relates to a device and 
method for determining the flow rate of gas entrapped fluids delivered in 
a pulsating flow, such as milk wherein the invention boasts an improved 
fluid level detection arrangement for determining flow rates with improved 
accuracy, and an improved temperature sensing arrangement for determining 
the temperature of the gas entrapped fluid with improved accuracy. 
II. Discussion of the Prior Art 
In recent years, it has become increasingly important for farmers to 
monitor and document the productivity of the cows within a given herd so 
as to ensure that dairy operations are being conducted with the highest 
degree of efficiency. A principal indicator of productivity is milk 
output, that is, the amount of milk that each cow is capable of rendering 
over a given period of time. By monitoring the milk output of each cow, a 
farmer can maximize the total amount of milk generated by the entire herd 
by singling out low-producing cows and replacing them with cows having 
greater ability to provide milk. Moreover, in that milk output is related 
to the overall health of a cow, farmers may also reduce the likelihood of 
having "tainted" milk enter the main holding tank by removing the 
low-producing, potentially ill cows from the milking herd, thereby 
improving the overall quality of the milk within the holding tank. In 
order to properly monitor milk output, it is essential to determine the 
true flow rate of the milk being delivered. However, obtaining an accurate 
assessment of flow rate during milking operations is particularly 
challenging due to the turbulent, pulsatile nature of the milk flow, as 
well as the foaming which results therefrom. 
U.S. Pat. No. 5,083,459, issued to Lind et al., illustrates an exemplary 
metering device for determining the flow rate of gas-entrapped fluids 
delivered in a pulsating flow, such as the milk rendered from cows during 
dairy operations. The flow meter of the '459 patent includes a 
multi-section, separable housing having a velocity reduction chamber for 
reducing the velocity of the incoming milk, a turbulence reduction chamber 
for reducing the amount of turbulence of the milk flow and for separating 
out foam, and a measurement chamber having a plurality of vertically 
spaced probe members for measuring the fluid level of the milk passing 
therethrough. More specifically, a "common probe" fluid level detection 
arrangement is employed, wherein a base probe is disposed proximate the 
bottom of the measurement chamber for receiving a driving signal and the 
upper probes are monitored the determine when conductivity is established 
between the base probe and any of the upper probes due to the rising and 
falling of the fluid within the measurement chamber. In this fashion, the 
fluid level within the measurement chamber can be continuously tracked and 
further correlated into flow rate such that the milk output for each cow 
within a herd may be monitored and documented. 
Although the physical structure of the housing is highly successful in 
reducing the turbulent, pulsatile fluid flow into a manageable fluid 
stream, the above-identified "common probe" fluid level detection 
arrangement occasionally results in inaccurate fluid level assessments 
when high and low fluid levels exist within the measurement chamber. As 
will be appreciated by those skilled in the art, this stems from the fact 
that the base probe is common to all fluid level measurements. More 
particularly, the impedance between the base probe and each upper probe is 
unique and fixed such that the impedance associated with a particular 
fluid level is different than the impedance associated with other fluid 
levels. By basing each fluid level determination on different base 
probe-to-upper probe impedances, the sensitivity of the "common probe" 
fluid level detection arrangement varies depending upon the particular 
fluid level. In practice, the varying sensitivity of the "common probe" 
fluid level detection arrangement may cause it to fail to detect when 
continuity is established between the base probe and the upper probes at 
high fluid levels, as well as detect continuity between the base probe and 
upper probes at low fluid levels when in actuality continuity has not been 
established. Missing continuity "hits" and detecting false continuity 
"hits" in this fashion causes the resulting determination of flow rate to 
be inaccurate and therefore less valuable in monitoring milk production. 
In addition to monitoring milk production, agriculturalists oftentimes find 
it helpful to monitor the temperature of each cow within a herd as a way 
to further ensure that the cows are in good health for optimizing the milk 
production of the herd. The traditional technique for assessing cow 
temperature requires manually inserting a thermometer in the rectum and/or 
vagina of the cow so as to obtain a direct assessment of body temperature. 
While this method does provide highly accurate cow temperature 
assessments, it is nonetheless is disadvantageously time consuming as well 
as undesirably messy. To avoid these drawbacks, various efforts have been 
undertaken to monitor cow temperature via indirect means so as to 
eliminate the need for manually inserting thermometers in the cows as 
described above. For example, in the system disclosed in the '459 patent 
to Lind et al., a temperature sensing element is typically inserted into 
the fluid line extending between the milk flow meter and the holding tank 
to monitor the temperature of the milk being extracted from each cow. Milk 
temperature, it is found, provides a general indication of the temperature 
of the cow being milked. While this method for indirectly monitoring cow 
temperature is generally useful, it is nonetheless flawed in that the 
temperature sensing element is positioned a fair distance from the actual 
cow and requires permanently altering the fluid line to insert the 
temperature sensing element therein. Disposing the temperature sensing 
element distal to the cow in this fashion subjects the temperature sensing 
element to fluctuations unrelated to cow temperature, such as temperature 
variations within the milking parlor, such that the resulting milk 
temperature measurements may not accurately reflect the true temperature 
of the cow. Permanently altering the fluid line results in increased costs 
in terms of both the time required to alter the fluid line, as well as the 
cost of material. 
A need therefore exists for an improved flow meter having an improved fluid 
level detection arrangement capable of consistently rendering accurate 
fluid level assessments for reliable flow rate determination. A further 
need exists for an improved flow meter having an internally disposed 
temperature sensing element for providing milk temperature assessments 
which accurately reflect the actual temperature of the cow. 
SUMMARY OF THE INVENTION 
It is accordingly a principal object of the present invention to provide an 
improved fluid level detection arrangement capable of consistently 
rendering accurate fluid level assessments for reliable flow rate 
determination. 
It is yet another principal object of the present invention to provide an 
improved flow meter having an internally disposed temperature sensing 
element for providing milk temperature assessments which accurately 
reflect the actual temperature of the cow. 
In accordance with the present invention, the foregoing objects and 
advantages are achieved by providing an improved flow meter for 
determining flow rates of pulsatile fluid flow. The improved flow meter 
comprises a fluid housing having a fluid inlet, a fluid outlet, a velocity 
reduction chamber in communication with the fluid inlet, a turbulence 
reduction chamber in communication with the velocity reduction chamber, 
and a fluid measurement chamber in communication with the velocity 
reduction chamber and the fluid outlet. The fluid measurement chamber has 
a plurality of electrically conductive probe members disposed in 
vertically spaced relation therewithin. Means are further provided for 
electrically determining conductivity between a preselected adjacent pair 
of the plurality of probe members as provided by the level of fluid within 
the measuring compartment. Means are also provided for converting the 
electrically conductive readings from the means for determining 
conductivity to a visual readout correlating to the flow of fluid through 
the fluid measurement chamber. 
In yet another broad aspect of the present invention, the above-identified 
objects are obtained by providing an improved flow meter for determining 
flow rates of pulsed fluids, comprising a fluid container, processing 
means, and temperature sensing means. The fluid container is of generally 
hollow construction having a fluid inlet, a fluid outlet, and a fluid 
measurement chamber disposed between the fluid inlet and the fluid outlet 
having a plurality of vertically spaced probe members disposed 
therewithin. The processing means is communicatively linked to the 
plurality of probe members for automatically tracking a fluid level within 
the fluid measurement chamber based on the conductivity of the fluid 
extending between each pair of vertically adjacent probe members and for 
correlating the fluid level within the fluid measurement chamber to 
determine a flow rate of the fluid passing through the fluid measurement 
chamber. The temperature sensing means is disposed proximate the fluid 
outlet and is communicatively linked to the processing means for sensing 
the temperature of the fluid passing through the fluid outlet. 
In still a further broad aspect of the present invention, the foregoing 
objects and advantages are obtained by providing a method of determining a 
flow rate of a fluid delivered in a pulsatile flow, comprising the steps 
of: (a) providing a fluid housing having a fluid inlet, a fluid outlet, a 
velocity reduction chamber in communication with the fluid inlet, a 
turbulence reduction chamber in communication with the velocity reduction 
chamber, a fluid measurement chamber in communication with the velocity 
reduction chamber and the fluid outlet, and a plurality of electrically 
conductive probe members disposed in vertically spaced relation within the 
fluid measurement chamber; (b) tracking the electrical conductivity 
between adjacent pairs of the plurality of probe members to determine an 
instantaneous fluid level within the fluid measurement compartment; and 
(c) calculating a flow rate based on the instantaneous fluid level within 
the measurement means. 
The foregoing features and advantages of the present invention will be 
readily apparent to those skilled in the art from a review of the 
following detailed description of the preferred embodiment in conjunction 
with the accompanying drawings and claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring initially to FIG. 1, shown is an improved flow meter 10 
constructed in accordance with a preferred embodiment of the present 
invention. The flow meter 10 comprises an upper housing member 12 and a 
lower housing member 14 which in use are sealably coupled about a baffle 
plate 16 via spring clips 18, 20. As will be explained in greater detail 
below, the upper and lower housing members 12, 14 are generally hollow in 
construction and include a variety of internally disposed structures for 
reducing the turbulent, pulsatile fluid flow from a milk pump 22 into a 
manageable fluid stream such that an accurate and reliable determination 
of milk flow rate can be obtained for a cow coupled to a milker 24. More 
specifically, with reference to FIG. 2, the upper housing member 12 
includes a velocity reduction chamber 26, while the lower housing member 
14 includes a turbulence reduction chamber 28, a metered orifice 30, and a 
measurement chamber 32. The velocity reduction chamber 26 is provided to 
reduce the velocity of the pulsating air/fluid mixture from the pump 22. 
The turbulence reduction chamber 28 serves to separate the air and fluid 
from the incoming air/fluid mixture from the velocity reduction chamber 
26. The metered orifice 30 is disposed at the entrance of the measurement 
chamber 32 to provide a clean fluid flow transition from the turbulence 
reduction chamber 28 to the measurement chamber 32 to aid in proper flow 
rate determination. The measurement chamber 32 is equipped with a 
plurality of vertically disposed probe members (not shown) which, in 
conjunction with a microprocessor 34, track the level of the fluid within 
the measurement chamber 32 for the purpose of determining instantaneous 
flow rate. After passing through the measurement chamber 32, the air 
previously removed in the turbulence reduction chamber 28 is thereafter 
remixed with the fluid for further transmission to a filter 36 en route to 
a holding tank 38. 
The structural detail of the exterior of the flow meter 10 will now be 
described with reference to FIGS. 3-5. The upper housing member 12 is 
generally dome-like in construction and includes a fluid inlet 40 and a 
flange member 42 having generally trapezoidal purchase points 44, 46 for 
slidably coupling with the upper portions of the spring clips 18, 20. The 
lower housing member 14 is similarly constructed with a fluid outlet 48 
and a flange member 50 having generally trapezoidal purchase points 52, 54 
for slidably coupling with the lower portions of the spring clips 18, 20. 
The lower housing member 14 has generally a front wall member 56 disposed 
opposite and generally parallel to a rear wall member 58, and opposing 
side walls 60, 62 which depend angularly inward from the flange member 50 
to a bottom member 64. A generally rectangular flange member 66 is 
provided extending perpendicularly outward from the rear wall member 58. 
Within the perimeter defined by the flange member 66 are the terminal ends 
of a base probe member 68, a first probe member 70, a second probe member 
72, a third probe member 74, a fourth probe member 76, a fifth probe 
member 78, a sixth probe member 80, a seventh probe member 82, and an 
eighth probe member 84. As will be set forth in greater particularity 
below, the probe members 68-84 are generally cylindrical and extend inward 
through the rear wall member 58 into the measurement chamber 32. The probe 
members 68-84 are composed of an electrically conductive material, such as 
stainless steel, and are disposed in staggered and parallel relation to 
one another to reduce the likelihood of spanning between probes when the 
fluid level in the measurement chamber 32 rises and falls due to 
pulsation. Although not shown, the flange member 66 may be equipped with a 
protective cover member for enclosing the terminal ends of the probe 
members 68-84 from the environment. 
Turning now to FIGS. 6-9, the structural details of the interior of the 
flow meter 10 are as follows. The baffle plate 16 is substantially flat 
having a first and second flow aperture 86, 88 formed therethrough on 
opposing ends of a centrally disposed and upwardly extending deflection 
member 90. An upper gasket member 92 and a lower gasket member 94 are 
provided on either side of the baffle plate 16 so as to establish a fluid 
tight seal between the baffle member 16 and the upper and lower housing 
members 12, 14, respectively, when the spring clips 18, 20 are snapped 
into place over the purchase points 46, 54 and 44, 52. The velocity 
reduction chamber 26 is defined between the upper housing member 12 and 
the baffle plate 16. The deflection member 90 has generally arcuate and 
sloping front 96, back 98, and side surfaces 100, 102 which serve to 
temporarily deflect the pulsatile incoming fluid as shown in phantom in 
FIGS. 6 and 7 so as to reduce the overall velocity of the fluid prior to 
passing through the first and second flow apertures 86, 88 into the 
turbulence reduction chamber 28. The turbulence reduction chamber 28 is 
bounded vertically between the baffle member 16 and the bottom member 64, 
horizontally between the angularly depending side walls 60, 62, and 
laterally between the front and rear wall members 56, 58. The turbulence 
reduction chamber 28 includes first and second baffle walls 104, 106 
extending in vertically parallel fashion from the front wall member 56 of 
the lower housing member 14. The first and second flow apertures 86, 88 in 
the baffle plate 16 are situated such that fluid passing through the first 
flow aperture 86 flows directly in the channel defined between the first 
baffle wall 104 and the side wall 62, while the fluid passing through the 
second flow aperture 88 flows directly in the channel defined between the 
second baffle wall 106 and the side wall 60. The bottom member 64 slopes 
downwardly at all points such that the fluid therein is forced to meander 
around the first and second baffle walls 104, 106 as shown in phantom in 
FIG. 8, thereby reducing the turbulence of the fluid prior to passing to 
the measurement chamber 32. 
The measurement chamber 32 comprises an elongated and generally rectangular 
housing formed by first and second side walls 108, 110 extending inward 
from the rear wall 58 of the lower housing member 14, a first end wall 112 
extending medially inward from the first side wall 108, and a second end 
wall 114 extending medially inward from the second side wall 110. The 
opposing edges of the first and second end walls 112, 114 define the 
metered orifice 30 leading into the measurement chamber 32. The opposing 
edges of the first and second end walls 112, 114 angle generally inward as 
they extend from the interior of the measurement chamber 32 towards the 
turbulence reduction chamber 28. The opposing edges of the first and 
second end walls 112, 114 also extend from the bottom member 64 of the 
housing member 14 in a vertically divergent fashion such that the 
resulting metered orifice 30 has a generally tapered shape. In an 
important aspect, the angling of the opposing edges of the first and 
second end walls 112, 114 provides a clean transition for the fluid 
flowing from the turbulence reduction chamber 28 into the measurement 
chamber 32 and the vertically tapered shape of the metered orifice 30 aids 
in proper flow rate determinations. The base probe 64 is positioned 
slightly below the plane of the metered orifice 30 at the approximate 
horizontal midline of the measurement chamber 32, while probes 70-84 are 
disposed within the measurement chamber 32 above the bottom plane of the 
metered orifice 30. As shown particularly in FIGS. 6 and 9, the probes 
70-84 are staggered relative to the horizontal midline and are spaced a 
predetermined and uniform distance from one another. Arranging the probe 
members 70-84 in staggered fashion reduces the likelihood of spanning 
between probes when the fluid level in the measurement chamber 32 rises 
and falls due to pulsation. Disposing the probe members 68-84 equi-distant 
from each other aids in the accurate assessment of fluid level which for 
proper determination of flow rate. 
Referring now to FIG. 10, shown is a schematic diagram of the improved flow 
meter illustrating in detail the "adjacent probe" fluid level detection 
arrangement of the present invention. The microprocessor controller 34 
forms the heart of the control circuit, distributing and receiving various 
control and data signals to coordinate the overall operation of the flow 
meter 10. In a preferred embodiment, the microprocessor controller 34 is 
coupled to a display 116 for communicating information to a user, a 
keyboard 118 for receiving input from a user, an "adjacent probe" fluid 
level detection circuit designated generally at 120 for detecting 
instantaneous fluid level within the measurement chamber 32, and a milk 
temperature sensing circuit 122 for assessing the temperature of the milk 
passing through the measurement chamber 32. The microprocessor controller 
34 may be powered through the use of either a battery module 124 for 
mobile operation or a DC power supply 126 for stanchion operation. The 
microprocessor controller 34 may be optionally coupled to supplemental 
circuits, such as a take-off driver 128 and a vacuum driver 130, and 
selectively programmed to detect slow or low flow conditions, as well as 
various alarm functions. 
In an important aspect of the present invention, the "adjacent probe" fluid 
level detection circuit 120, in cooperation with the microprocessor 
controller 34, continually tracks fluid level within the measurement 
chamber 32 by applying a predetermined driving signal to a selected one of 
the probe members 68-82 while monitoring the immediately superior probe 
member to determine whether continuity is established therebetween within 
a given time period. Continuity between the selected pair of adjacent 
probe members will only be established if the fluid level within the 
measurement chamber 32 is such that the fluid therein contacts both probe 
members simultaneously. Therefore, if continuity is detected it indicates 
that the fluid level within the measurement chamber 32 is at least as high 
as the uppermost probe member of the selected pair of adjacent probe 
members. Conversely, if continuity is not detected it indicates that the 
fluid level within the measurement chamber 32 is lower than the uppermost 
probe member of the selected pair of adjacent probe members. Based on this 
continuity information, the microprocessor controller 34 then selectively 
re-directs the predetermined driving signal to one of the immediately 
superior probe member (if continuity was established) and the immediately 
inferior probe member (if continuity was not established). The 
aforementioned process is then repeated to assess continuity between the 
newly selected pair of adjacent probe members to once again gain an 
indication of fluid level relative to that particular pair of adjacent 
probe members. The foregoing steps are repeated in quick succession such 
that the fluid level within the measurement chamber 32 can be accurately 
tracked irrespective of the pulsatile, turbulent nature of the fluid flow. 
By tracking the fluid level within the measurement chamber 32 in this 
fashion, the microprocessor controller 34 may easily render a highly 
accurate determination of flow rate. 
The "adjacent probe" fluid level detection circuit 120 forms an important 
aspect of the present invention and is therefore described with 
particularity as follows. A first multiplexer 132 and a second multiplexer 
134 are configured to receive probe select input data in parallel from the 
microprocessor controller 34 via probe select lines 136. The first 
multiplexer 132 is further coupled to a driving circuit 138 via an input 
line 140 and to the probe members 68-82 via output lines 142. The second 
multiplexer 134 is coupled to probe members 70-84 via input lines 144 
having filtering capacitors C1-C8 disposed therealong and to an impedance 
threshold detection circuit 146 via an output line 148. The driving 
circuit 138 is coupled to the microprocessor controller 34 via a line 150 
and to a voltage reference circuit 152 via lines 154, 156. A current 
limiting resistor R1 is provided extending between line 150 and ground. 
The driving circuit 138 includes a first amplifier A1 and a second 
amplifier A2 configured in a push-pull relationship with a pnp transistor 
Q1. More specifically, the inverting input of amplifier A1 and the 
non-inverting input of amplifier A2 are tied together and coupled to line 
150, the non-inverting input of amplifier A1 is coupled to a first node 
158 of the voltage reference circuit 152, and the inverting input of the 
amplifier A2 is coupled to a second node 160 of the voltage reference 
circuit 152. The output of the amplifier A1 and the base of the transistor 
Q1 are coupled together with a resistor R3. The emitter of the transistor 
Q1 is tied to power supply +V, while the collector is tied to the output 
of the amplifier A2 with a resistor R2 and to the first multiplexer 132 
via line 140. The voltage reference circuit 152 is a voltage divider 
having a resistor R4 extending between the power supply +V and the first 
node 158, a resistor R5 extending between the first node 158 and the 
second node 160, a resistor R6 extending between the second node 160 and 
ground, and a capacitor C9 extending from the first node 158 to ground. 
The second node 160 is coupled directly to the inverting input of an 
amplifier A3, while the first node 158 is coupled to the non-inverting 
input of an amplifier A4 via a resistor R7. A resistor R8 further couples 
the non-inverting input of amplifier A4 to the output thereof for return 
to the microprocessor controller 34 via line 162. The inverting input of 
the amplifier A4 is coupled to the output of the amplifier A3 via a diode 
D1. A resistor R9 is provided between the power supply +V and the anode of 
diode D1, while a capacitor C10 extends between the anode of diode D1 and 
ground. The non-inverting input of the amplifier A3 is coupled to the 
second multiplexer 134 via a line 148 which includes a resistor R10 
extending to ground. 
In operation, the microprocessor controller 34 selectively transmits a 
pulsed driver enable signal to the driving circuit 138 on line 150. The 
push-pull arrangement of the driving circuit 138, in turn, generates a 
driving signal on line 140 for transmission to the first multiplexer 132. 
The first multiplexer 132 selectively directs the driving signal received 
on line 140 to a preselected one of the probe members 68-82 depending upon 
the probe select data being transmitted to the first and second 
multiplexers 132, 134 on probe select lines 136. Due to the parallel and 
shifted coupling between the output lines 142 and input lines 144, the 
second multiplexer 134 establishes electrical communication between the 
impedance threshold detection circuit 146 and the probe member located 
immediately superior to the probe member receiving the driving signal from 
the first multiplexer 132. The impedance threshold detection circuit 146 
interrogates the return signal on line 148 to determine whether the 
driving signal being applied to the lower probe member of the adjacent 
pair is received at the upper probe member of the adjacent pair during the 
application of the driving signal. It will be appreciated that the driving 
signal will only be received at the upper probe member of the adjacent 
pair if electrical continuity is established therebetween. With the probe 
members 68-84 disposed in a vertically spaced fashion within the 
measurement chamber 32, electrical continuity between any pair of adjacent 
probe members will only be established if the fluid level within the 
measurement chamber 32 is such that fluid establishes a conductive path 
therebetween. As such, if the driving signal is received at the upper 
probe member it indicates that the fluid level within the measurement 
chamber 32 is at least as high as the upper probe member of the selected 
adjacent pair. Conversely, if the driving signal is not received at the 
upper probe member it indicates that the fluid level within the 
measurement chamber 32 is less than the height of the upper probe member. 
By knowing the vertical location of the probe members 68-84 within the 
measurement chamber 32, the microprocessor controller 34 is capable of 
translating this continuity information into an accurate fluid level 
determination. The microprocessor controller 34, in turn, computes 
instantaneous flow rate based on the fluid level within the measurement 
chamber 32, the dimensions of the metered orifice 30, and the dimensions 
of the fluid outlet 48. 
The operation of the impedance threshold detection circuit 146 will now be 
explained as follows. The signal on the return line 148 will remain in a 
low or off state unless and until continuity is established between the 
selected pair of adjacent probe members such that the driving signal 
applied to the lower probe member of the adjacent pair is received at the 
upper probe member of the adjacent pair. In a preferred embodiment, the 
voltage reference circuit 152 is configured such that the voltage level at 
first node 158 will be approximately two-thirds (2/3) of the supply 
voltage (+V), while the voltage level at the second node 160 will be 
approximately one-third (1/3) of the supply voltage (+V). In that the 
second node 160 is tied to the inverting input of amplifier A3, the output 
of amplifier A3 will therefore remain low until the signal on return line 
148 causes a voltage drop across resistor R10 which exceeds the voltage at 
the second node 160. The amplifier A4 is disposed in a normally high 
configuration such that the output on line 162 will be maintained in a 
high state until the voltage level at the inverting input thereof exceeds 
the voltage level at the non-inverting input thereof As such, when 
continuity is not established between the selected adjacent probe members 
the voltage drop across resistor R10 will not accrue to exceed the voltage 
level at the inverting input of amplifier A3 and the resulting output of 
amplifier A3 will therefore be maintained low. The low output of amplifier 
A3 consequently shorts out the capacitor C10 and maintains the inverting 
input of amplifier A4 low such that the output signal on line 162 is 
maintained high. The microprocessor controller 34 interprets this as 
representing a lack of continuity between the selected adjacent pair of 
probe members. In the instance that continuity is established between the 
selected adjacent probe members, the voltage drop across resistor R10 will 
accrue to point where it exceeds the voltage level at the inverting input 
of the amplifier A3 such that the resulting output of amplifier A3 will 
switch into a high state. The moment the output of amplifier A3 switches 
into a high state capacitor C10 will begin charging. When the charge 
within capacitor C10 exceeds the voltage level at the non-inverting 
terminal of amplifier A4, which in the preferred embodiment is the voltage 
at second node 160, the output signal on line 162 immediately drops to a 
low state. The time constant of capacitor C10 is preferably chosen such 
that its charge will only exceed the voltage at the non-inverting input of 
amplifier A4 if continuity between the adjacent probe members is 
maintained for a predetermined duration. In this fashion, the capacitor 
C10 serves as a filter for screening out momentary continuity hits which 
may be attributable to causes other than the fluid being at that 
particular level within the measurement chamber 32. 
In a preferred embodiment, the driver enable signal will be applied to the 
driving circuit 138 for a predetermined period of time unless it is 
determined within that period that continuity has been established between 
the selected adjacent pair of probe members. If continuity is detected 
during the application of the driving signal, the microprocessor 
controller 34 will stop applying the driver enable signal to the driving 
circuit 138, increment the probe selection by one level, and thereafter 
re-apply another driver enable signal to the driving circuit 138. With the 
probe selection incremented by one level, the first multiplexer 132 will 
direct the new driving signal to the probe member located directly above 
the probe member which received the previous driving signal, while the 
second multiplexer 134 will connect the impedance threshold detection 
circuit 146 to the probe member located immediately superior to the probe 
member which receives the new driving signal. If continuity between the 
adjacent pair of probe members is not detected within a predetermined 
period of time, such as 20 milliseconds, the microprocessor controller 34 
will automatically stop applying the driver enable signal to the driving 
circuit 138, decrement the probe selection by one level, and thereafter 
re-apply another driver enable signal to the driving circuit 138. In this 
case, decrementing the probe selection will cause the first multiplexer 
132 to direct the new driving signal to the probe member immediately below 
the probe member which received the previous driving signal and cause the 
second multiplexer 134 to connect the impedance threshold detection 
circuit 146 to the probe member located immediately superior to the probe 
member which receives the new driving signal. 
For example, if the preselected pair of adjacent probe members consists of 
the fourth and fifth probe members 76, 78, the first multiplexer 132 will 
direct the pulsed driving signal to the fourth probe member 76 while the 
second multiplexer 134 establishes a communication link between the fifth 
probe member 78 and the impedance threshold detection circuit 146. The 
impedance threshold detection circuit 146 then continuously monitors the 
signal on line 148 to detect whether the driving signal applied to the 
fourth probe member 76 is being received at the fifth probe member 78. If 
the driving signal is received at the fifth probe member 78 within a 
predetermined period, the impedance threshold detection circuit 146 will 
produce a low output signal on line 162 indicating to the microprocessor 
controller 34 that continuity has been established between the fourth and 
fifth probe members 76, 78. The microprocessor controller 34 will then 
stop applying the driver enable signal on line 150, increment the probe 
selection by one such that the newly selected adjacent pair consists of 
the fifth and sixth probe members 78, 80, and re-apply the driver enable 
signal to the driving circuit 138. In this arrangement, the first 
multiplexer 132 directs the new driving signal to the fifth probe member 
78 and the second multiplexer 134 connects the sixth probe member 80 with 
the impedance threshold detection circuit 146 for monitoring continuity 
therebetween. Conversely, if the driving signal is not received at the 
fifth probe member 78 within a predetermined period the impedance 
threshold detection circuit 146 will maintain the normally high output 
signal on line 162 indicating to the microprocessor controller 34 that 
continuity has not been established between the fourth and fifth probe 
members 76, 78. The microprocessor controller 34 will consequently 
decrement the probe selection by one such that the newly selected adjacent 
pair consists of the third and fourth probe members 74, 76 and thereafter 
re-apply the driver enable signal to the driving circuit 138. The first 
multiplexer 132 will therefore direct the new driving signal to the third 
probe member 74 while the second multiplexer 134 connects the fourth probe 
member 76 with the impedance threshold detection circuit 146 for 
monitoring continuity therebetween. The foregoing sequence will be 
repeated in quick succession such that the microprocessor controller 34 
may accurately track the fluid level within the measurement chamber 32 for 
subsequent calculation of fluid flow. 
The improved milk temperature sensing arrangement of the present invention 
will now be described as follows. As shown generally in FIG. 10, the 
temperature sensing circuit 122 is coupled to a temperature sensing 
element 164 disposed within a bore formed in the base probe member 68 via 
a line 166 and to the microprocessor controller 34 via a line 168. The 
position of the temperature sensing element 164 within the base probe 68 
forms an important aspect of the present invention in that milk 
temperature is sensed at a point in close proximity to the actual cow 
being milked to thereby provide an indirect yet accurate assessment of cow 
temperature. The microprocessor controller 34 monitors the output of the 
temperature sensing circuit 122 on line 168 and serves to track the milk 
temperature within the measurement chamber 32 during the milking of each 
cow. The microprocessor controller 34 may be optionally configured to 
automatically store all or selective portions of the milk temperature data 
obtained by the temperature sensing circuit 122. In this fashion, the 
history for each cow can be analyzed to determine trends and/or indicate 
which animals should be replaced within the milk production herd. The 
temperature sensing element 164 can be any number of commercially 
available linear or non-linear temperature sensing devices, including but 
not limited to thermistors and temperature dependent resistors. 
With reference to FIG. 11, shown is a schematic diagram illustrating in 
detail the milk temperature sensing circuit 122 shown generally in FIG. 
10. The temperature sensing element 164 is disposed within the base probe 
member 68 as shown in phantom. A current source circuit 170 is provided 
including a pnp transistor Q2, an amplifier A5, a zener diode D2, and 
resistors R11 and R12. The base of the transistor Q2 is tied directly to 
the output of amplifier A5. The emitter of the transistor Q2 is tied to 
the inverting input of amplifier A5 and to the power supply (+V) through 
the resistor R12. The non-inverting input of the amplifier A5 is tied to 
the junction between the zener diode D2 and the resistor R11, wherein the 
zener diode D2 is tied to the power supply (+V) and the resistor R11 is 
tied to ground. The collector of the transistor Q2 is tied to the 
temperature sensing element 164 via line 166. In addition to being 
connected to the temperature sensing element 164, the current source 
circuit 170 is further coupled to the inverting input of an amplifier A6 
via a resistor R13 and to a capacitor C11 coupled to ground. The inverting 
input and the output of the amplifier A6 are coupled together with a 
resistor R14 disposed in parallel to a capacitor C12. The non-inverting 
input of the amplifier A6 is coupled temperature calibration circuit 172 
comprising a resistor R17, a resistor R18, and a capacitor C14. The 
resistor R18 and capacitor C14 are tied to ground, while the resistor R17 
is tied to a potentiometer resistor R16. The potentiometer R16 is further 
tied to ground and to the output of an amplifier A7. The amplifier A7 is 
configured as a buffer with the output tied to the inverting input and the 
non-inverting input tied to a resistor R15, a capacitor C13, and a zener 
diode D3. The capacitor C13 and the zener diode D3 are tied to ground 
while the resistor R15 is coupled to the power supply (+V). 
The voltage signal generated by the temperature sensing element 164 is 
derived from the constant current source circuit 170. Due to the resulting 
voltage drop across resistor R13, then, the current level at the inverting 
input of amplifier A6 varies in proportion to the sensor signal generated 
by the temperature sensing element 164. The temperature calibration 
circuit 172 advantageously allows the voltage level at the non-inverting 
input of amplifier A6 to be selectively set so as to provide a meaningful 
voltage reference from which accurate temperature measurements may be 
derived based on the output of the temperature sensing element 164. More 
specifically, the potentiometer resistor R16 may be selectively adjusted 
to modify the voltage divider established by the resistors R17 and R18 to 
thereby produce a specific voltage level at a node 174 coupled to the 
non-inverting input of the amplifier A6. With the voltage at the 
non-inverting input maintained at a predetermined level in this fashion, 
any variations in the voltage level at the inverting input due to 
temperature changes results in a corresponding change in the analog output 
from the amplifier A6. In that average cow temperature is approximately 
101 degrees Fahrenheit, the temperature calibration circuit 172 is 
preferably calibrated such that the voltage level at the non-inverting 
input of the amplifier A6 provides an appropriate reference for covering a 
temperature range between 90 and 115 degrees Fahrenheit. The 
microprocessor controller 34 continuously receives the output of the 
temperature sensing circuit 122 via line 168 and, in a preferred 
embodiment, samples this output signal on the order of 10 times per second 
to provide a digital readout of the temperature on the display 116 shown 
in FIG. 10. 
In light of the foregoing, the improved flow meter of the present invention 
boasts several distinct advantages of the known prior art. First, the 
improved flow meter advantageously employs an improved fluid level 
detection arrangement for accurately tracking the fluid level within the 
measurement chamber so as to provide more reliable determinations of flow 
rate. Second, the improved flow meter advantageously includes an 
internally disposed temperature sensing element which, in conjunction with 
the aforementioned temperature sensing circuit, provides the ability to 
accurately monitor the temperature of the milk within the flow meter so as 
to provide a more reliable indirect assessment of cow temperature than has 
heretofore been provided. 
This invention has been described herein in considerable detail in order to 
comply with the Patent Statutes and to provide those skilled in the art 
with the information needed to apply the novel principles and to construct 
and use such specialized components as are required. However, it is to be 
understood that the invention can be carried out by specifically different 
equipment and devices, and that various modifications, both as to the 
equipment details and operating procedures, can be accomplished without 
departing from the scope of the invention itself