Abstrict
A device for testing the operability of a blood pressure monitor.
The device includes a signal generator for generating a plurality
of different output signals simulating a variety of static blood
pressure levels. A plurality of display devices are included, each
device corresponding to one of the given static blood pressure levels.
Control circuitry coupled to a single push button switch simultaneously
selects a different blood pressure level to be generated and energizes
its corresponding display device upon each sequential activation
of the switch.
Claims
The embodiments of the invention in which an exclusive property
or privilege is claimed are defined as follows;
1. A device for testing the operability of a blood pressure monitor,
said device comprising:
generator means for selectively generating a plurality of output
signals, each output signal having a different signal level corresponding
to preselected static blood pressure levels for testing the operability
of the blood pressure monitor;
a plurality of display devices, each device corresponding to one
of the preselected static blood pressure levels;
a push button switch;
control means coupled to said switch, said generator means, and
to said display devices, said control means providing control signals
operative for simultaneously selecting a different blood pressure
level output signal for generation by said generator means and for
energizing its corresponding display device upon each sequential
activation of the switch.
2. The device of claim 1 which further comprises:
a battery for providing power to the device; and
low battery indicator means coupled to the battery, operative to
provide a visual indication when the voltage level from the battery
has fallen below a predetermined reference level.
3. The device of claim 2 which further comprises timer means for
automatically disconnecting said battery from internal device components
if said switch is not activated within a given time period.
4. In a device for testing the operability of a blood pressure
monitor, said device including a bridge network having a plurality
of the resistive legs, an input coupled to an excitation signal
from the blood pressure monitor, and an output coupled to the blood
pressure monitor for supplying signals to the monitor for testing
its operability, the improvement comprising:
a plurality of resistors having one of their ends commonly coupled
to one node of the bridge network;
multiplexer means having a plurality of outputs, each of said outputs
being coupled to the other end of separate ones of said resistors,
said multiplexer means having an input coupled to an adjacent node
of said bridge network, and said multiplexor means having control
inputs operative to selectively couple one of said outputs to said
input thereby selectively coupling one of said resistors across
the bridge leg bounded by said nodes, said resistors having different
resistive values such that the output of said bridge network provides
a plurality of different static blood pressure levels to the monitor
for testing the operability thereof;
a plurality of display devices, each device associated with one
of the resistors for generating a given static blood pressure level;
decoder means having a plurality of outputs, each output coupled
to one of said display devices, said decoder means having a control
input for selecting one of said outputs for activating its associated
display device;
a single manually selectable push button select switch; and
control circuit means coupled between the switch and the control
inputs of both said multiplexer and said decoder means, operative
to successively select one of said resistors and simultaneously
activate the display device associated with the static blood pressure
level generated by the selected resistor upon each sequential activation
of the switch.
5. The improvement of claim 4 wherein said control means comprises
a first counter, operative to increase its output signal count by
one for each sequential activation of the switch.
6. The improvement of claim 5 wherein said control means further
comprises;
zero detector means coupled between the output of said first counter
and said multiplexer, operative to inhibit the multiplexer when
the counter output is zero to thereby prevent said resistors from
being coupled to said bridge betwork upon initialization of the
device to permit zeroing.
7. The improvement of claim 6 wherein said control means further
comprises:
a potential source;
a power switch having an input coupled to the potential source
and an output coupled to electrical components in the device;
a first flip flop having set and reset inputs coupled for sequential
receipt of set and reset signals upon activation of said selector
switch, and an output;
a second flip flop having a set input coupled to the output of
the first flip flop, and an output coupled to said power switch,
operative to enable said power switch upon initial activation of
said selector switch whereby power is supplied to the electrical
components of the device.
8. The improvement of claim 7 which further comprises:
means for coupling the output of said first flip flop to said first
counter for incrementing it upon each sequential activation of the
selector switch; and
RC delay means for gating said first flip flop output to said first
counter after a predetermined time period has elapsed from power
being initially applied to the device components whereby to initialize
the count signal in said first counter.
9. The improvement of claim 8 which further comprises:
timer means for disabling said power switch after a given time
period has elapsed without further activation of said selector switch.
10. The improvement of claim 9 wherein said timer means comprises:
oscillator means for providing a series of pulses;
second counter means having an input coupled for receipt of said
pulses from the oscillator means, said second counter having an
output coupled to a reset input of said second flip flop for resetting
same to thereby disable said power switch when the second counter
reaches a given count; and
means for coupling the output of said first flip flop to a reset
input of said second counter, operative to reset the second counter
upon each activation of said selector switch whereby power is supplied
to the circuitry as long as the selector switch has been activated
before the second counter reaches said given count.
11. The improvement of claim 10 wherein said display devices are
light emitting diodes having their associated cathodes separately
coupled to an output of the decoder means and having their anodes
commonly connected together; and
wherein said oscillator means is further coupled to said commonly
connected light emitting diode anodes for providing duty cycle control
of the ultimately selected light emitting diode thereby minimizing
power dissipation thereof.
12. The improvement of claim 11 wherein the source of potential
is a battery, and wherein said improvement further comprises:
battery detector means coupled to the battery for detecting a low
battery condition and activating a display to indicate said detected
condition.
13. The improvement of claim 12 wherein said battery detector means
comprises:
a comparator having one input coupled to the output of said power
switch and another input coupled to a predetermined voltage level,
operative to provide an energization signal at its output to activate
the battery detector display device when the voltage level at said
one input falls below said predetermined level.
14. Electrical circuitry for initializing and incrementing a counter
upon sequential activation of a single push button switch, said
circuitry comprising:
a single push button switch;
a potential source;
a power switch having an input coupled to the potential source
and an output;
a first flip flop having set and reset inputs coupled for sequential
receipt of power from said source upon each activation of said push
button switch thereby setting and resetting said first flip flop,
said first flip flop having an output;
a second flip flop having a set input coupled to the output of
the first flip flop, said second flip flop having an output;
counter means having a clock input for incrementing the count signal
output of said counter means, said counter having a reset input
for resetting the count signal, and a power input coupled to the
output of said power switch for controlling power to the counter
means;
means for coupling the output of said second flip flop to the power
switch, operative to enable said power switch on the first activation
of said selector switch;
delay means coupled to the output of said power switch, operative
to provide a reinitializing signal to the reset input of the counter
means until a given time period has elapsed from power being initially
applied to the counter means; and
gating means coupled to the output of said delay means and to the
output of said first flip flop, operative to increment the count
signal in said counter by providing a pulse to said clock input
of the counter means upon each subsequent sequential activation
of said selector switch.
15. The circuitry of claim 14 which further comprises:
timer means coupled to a reset input of said second flip flop,
operative to reset the second flip flop to thereby disenable said
power switch if said selector switch has not been activated within
a predetermined time period.
Description BACKGROUND OF THE INVENTION
This invention relates to test devices and, more particularly,
to a device for testing the operability of a blood pressure monitor.
In U.S. Ser. No. 938,430, filed Aug. 31, 1978, (now U.S. Pat. No.
4,205,386) entitled "Electrocardiographic and Blood Pressure
Waveform Simulator Device", assigned to the assignee of the
present invention, there is disclosed a battery operated device
for generating a plurality of different static blood pressure signals
for testing the operability of a blood pressure monitor. The different
static blood pressure levels were selected by pressing separate
buttons on the housing of the simulator device. This device has
provided extremely satisfactory results. However, the use of the
many different selector switches added to the manufacturing costs
of the device and was somewhat inconvenient to the user. It was
also important to insure that each separate switch was operating
properly so that each one makes the proper electrical connection.
Although the switches were labeled, it was often not readily apparent
to the user exactly which static blood pressure level was being
generated. Moreover, the battery has a tendency to run down if the
user did not press the correct power switch to turn the device off
after use.
SUMMARY OF THE INVENTION
The present invention provides unique improvements to the device
disclosed in above-identified patent application. According to the
present invention, means are provided for generating a plurality
of different output signals corresponding to different static blood
pressure levels for testing the operability of a blood pressure
monitor. A plurality of display devices are also included, with
each device corresponding to one of the generated static blood pressure
levels. Control means are coupled to a push button switch. The control
means is operative for simultaneously selecting a different blood
pressure level and energizing its corresponding display device upon
each sequential activation of the switch. Preferably, there is only
one switch provided for the device and it controls on/off functions
as well as the level selector function noted above. Another aspect
of this invention includes the provision of an automatic shut-off
timer which automatically removes power from the electrical circuitry
if the switch is not activated within a predetermined time period
thereby preserving battery power.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the present invention
will become apparent upon reading the following specification and
by reference to the drawings in which:
FIG. 1 is a top plan view of a device made according to the teachings
of the present invention in use with a blood pressure monitor;
FIG. 2 is a functional block diagram of the preferred embodiment
of the electrical circuitry of this invention; and
FIG. 3 is an electrical schematic showing the details of the functional
blocks shown in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the simulator device 10 of the present invention
includes a housing 12 which contains the electrical circuitry shown
schematically in FIGS. 2 and 3. A plurality of separate light emitting
diodes (LED) L1-L10 are mounted in the top panel of housing 12.
LED's L1-L8 correspond to static blood pressure levels of 300, 250,
200, 100, 80, 50, 15 and 0 millimeters of mercury, respectively.
The particular static blood pressure level to be generated is selected
by sequential activation of selector switch 14. The generated static
blood pressure levels are coupled to blood pressure monitor 16 over
cable 18. Upon the first activation of switch 14, the device 10
is initialized and the zero LED L8 is activated. The user can calibrate
or zero the output of the device 10 by knob 20 which is coupled
to appropriate adjustment means within the electrical circuitry
to be later described. Further activation of switch 14 sequentially
selects signals simulating progressively increasing different static
blood pressure levels to be supplied over cable 18 to monitor 16.
In such manner, the user may calibrate monitor 16 to the various
simulated static blood pressure levels generated by device 10. LED
L9 is activated when device 10 is provided with a dynamic waveform
generator capability such as that described in the above-identified
U.S. Pat. No. 4,205,386 which is hereby incorporated by reference.
LED L10 will be energized when the battery power falls below a predetermimed
level.
Turning now to FIG. 2, switch 14 is a spring-loaded momentary single
pole push button switch which serves, upon each activation to set
and then reset RS flip flop 22 by coupling power from battery 24
to its set and then to its reset inputs. The first activation of
switch 14 momentarily sets flip flop 22 which, in turn, sets flip
flop 25 whose output is coupled to power switch 26 to thereby enable
it and supply power Vo to the other electrical components in the
circuitry. Low battery indicator circuitry 28 monitors the voltage
level of battery 24 and provides a visual indication via LED L10
if the voltage level falls below a predetermined limit.
Binary counter 34 is enabled for receipt of input pulses initiated
by switch 14 only after an initializing delay time period determined
by RC time delay circuit 30. Binary counter 34 provides a selector
code simultaneously to decoder 36 and multiplexer 38. Zero detector
circuitry 40 detects a zero output count from counter 34 and inhibits
multiplexer 38 so that the device 10 may be initially zeroed by
an appropriate adjustment of variable resistor R34. Alternatively,
the monitor under test may be zeroed at this time according to procedures
provided by the monitor manufacturer. Nonzero outputs from counter
34 cause circuitry 40 to enable multiplexer 38 to couple one of
the static level determining resistors 39 into a leg of the interface
bridge network 42. Bridge network 42 accepts an excitation signal
from the blood pressure monitor 16 at its input. The output of the
bridge 42 is coupled to the blood pressure monitor 16. On each subsequent
sequential activation of switch 14, a different static level determining
resistor 39 is coupled acrossed one leg of bridge 42 to unbalance
the bridge and provide an output signal corresponding to the various
different static blood pressure levels.
Simultaneously with the generation of the particular simulated
static blood pressure level, decoder 36 activates the particular
LED in display module 44 associated with the particular simulated
static blood pressure level generated.
Display power control circuitry 46 provides duty cycle control
for the selected LED such that power dissipation is kept to a minimum.
Automatic timer circuitry 48 coupled to logic control circuitry
32 and flip flop 25 monitors the elapsed time between each switch
14 activation. If the switch 14 is not activated within a predetermined
time period, timer 48 will reset flip flop 25 to turn off power
switch 26 thereby removing power from the device and prolonging
battery life.
A dynamic blood pressure waveform simulator 50 may be included
as an option. This option includes a time varying waveform generator
52 which is coupled to another leg of bridge 42 through photocoupler
54. In such manner, the device 10 may provide dynamic waveforms
for further enhancing the testing of monitor 16. When the dynamic
simulator 50 is in use, LED L9 is activated. Dynamic waveform simulator
50 may be that disclosed in detail in the above-identified U.S.
Pat. No. 4,205,386.
Turning now to FIG. 3, the details of the electrical components
making up the functional blocks in FIG. 2 will be described. To
aid the reader, the components making up the functional blocks are
encompassed by dotted lines.
Flip flop 22 is comprised of two cross coupled NOR gates 56 and
58. One input of gate 56 serves as the reset input, with one input
of gate 58 serving as the set input for the flip flop 22. The output
of gate 56 serves as the Q output which is coupled to one input
of a similarly cross coupled NOR gate pair consisting of gates 60
and 62 making up flip flop 25.
When switch 14 is first activated, its plate closes the normally
open N/O contacts to set flip flop 22. The Q output from flip flop
22 sets flip flop 25 and causes its Q output to fall to a logical
zero level. This logical zero level pulls the base of PNP transistor
Q1 low thereby turning it on and coupling the power from battery
24 to its collector output labeled V.sub.o. While only some of the
components in FIG. 3 are labeled with a V.sub.o power input, all
of the components except flip flops 22 and 25 and multiplexer 38
are powered by the V.sub.o output from power switch 26.
RC time delay circuitry 30 is utilized to initialize binary counter
34. Until capacitor C3 charges to a predetermined level, the reset
input of counter 34 is held at a logical one level via inverter
64 and the clock input is held at a logical zero level by the operation
of NAND gate 66. As soon as capacitor C3 charges to the appropriate
level, the outputs of gates 64 and 66 change state such that counter
34 will now be capable of providing incremental outputs upon receipt
of further clock signals.
When the user releases switch button 14, flip flop 22 is reset
thereby placing its Q output in a logical zero state. However, flip
flop 25 is not reset, and its Q output remains low to keep power
switch 26 enabled. Instead, flip flop 25 will be reset only upon
receipt of appropriate signals from counter 34 and the auto timer
circuitry 48 which will be later described.
Counter 34 is a known binary counter which provides increasing
binary count signals on its output lines 61, 63, 65, and 67 upon
each receipt of an input clock signal. Counter 34 may be that manufactured
by Motorola Semiconductors as Component No. MC14024B. When switch
14 is first activated, counter 34 is initialized such that its output
lines provide a count value of zero. The least significant counter
output lines 61, 63, and 65 are coupled to zero detector circuitry
40. Detector circuitry 40 includes NOR gate 68, NOR gate 70 wired
as an inverter, NAND gate 72, and inverter 74 whose output is coupled
to the Inhibit input of multiplexer 38. When zero detector circuitry
40 detects a zero count signal from counter 34 it provides a logical
one level to the Inhibit input of multiplexer 38. Multiplexer 38
is an analog switching device which couples input line 76 with a
selected one of its output lines 78-90 depending upon the count
signal from counter 34 applied to its control or select inputs.
Multiplexer 38 may be that manufactured by Motorola Semiconductors
as Component No. MC14051B. However, when inhibited, multiplexer
38 does not couple input line 76 to any of its output lines 78-90.
This permits the user to zero the blood pressure monitor 16 by an
appropriate adjustment.
Output lines 61, 63, and 65 from counter 34 are also coupled to
select inputs of decoder 36. Decoder 36 is a BCD to decimal decoder
such as that manufactured by Motorola Semiconductors as Component
No. MC1402B. Depending upon the count signal on select input lines
61, 63, and 65, decoder 36 selects one of its output lines. As can
be clearly seen in FIG. 3, the output lines of decoder 36 are coupled
to selected ones of LED's L1-L8. The output lines of decoder 36
each include an inverter/buffer 92 which serves as a current sink
for its corresponding LED. When a particular output line from decoder
36 is selected it is driven high and the output of the corresponding
buffer inverter 92 is driven low thereby permitting its associated
LED to turn on.
When switch 14 is first activated, the count signal on the decoder
36 select input lines causes it to select LED L8 to indicate a zero
condition. The anodes of all of the LED's L1-L8 are commonly connected
to display power control circuitry 46. Circuitry 46 includes a crystal
94 driving oscillator circuitry comprised of inverters 96, 98 and
an appropriate RC network comprised of resistor R15 and capacitor
C1. The oscillator network provides clock pulses to a binary counter
100. Counter 100 is a 14 stage binary counter such as that manufactured
by Motorola Semiconductors as Component No MC14020B. As is known
in the art, appropriate selection of the output pins of such a counter
will provide pulses at a particular frequency. Output line 102 from
counter 100 provides clock pulses at a frequency of about 60 Hertz.
This alternating signal is coupled through transistor Q2 via current
limiting resistors R1-R8 to the anodes of all of the LED's L1-L8.
This alternating signal provides a 50% duty cycle control for the
LED's to thereby minimize power dissipation.
On the next activation of switch 14, the momentary logical one
signal on the Q output of flip flop 22 causes gate 66 to transcend
to a logical zero level, such transition creating a clock pulse
to counter 34 thereby incrementing the count signal on its output
lines. Circuitry 40 now detects a nonzero condition and removes
the inhibit signal from multiplexer 38. The particular count signal
on the select inputs to multiplexer 38 causes it to couple output
line 78 to the common input line 76. This causes resistor R20 to
be connected in parallel across resistor R31 of bridge network 42.
The value of resistor R20 is chosen such that it will unbalance
bridge 42 to such extent that its output will provide a voltage
level equivalent to 15 millimeters of mercury (mmHg).
Simultaneously with the generation of the 15 mmHg static blood
pressure level signal, LED L7 is activated to give the user a visual
indication that this particular static blood pressure level is being
generated by device 10. This is accomplished in the same manner
as previously disclosed in connection with the activation of the
zero LED L8. However, since the inputs to decoder 36 now provide
a different count signal, LED L7 is energized instead of LED L8.
Upon each next activation of switch 14, counter 34 will again be
incremented thereby simultaneously providing control signals to
decoder 36 and multiplexer 38 to select a different LED to indicate
the new static blood pressure level which is being generated due
to the coupling of a different resistor into bridge network 42.
Thus it can be seen that the first activation of switch 14 inhibits
multiplexer 38 and lights zero LED 8. With each succeeding activation
of switch 14, multiplexer 38 couples lines 78-90 to the input line
76 and simultaneously, decoder 36 activates corresponding LED lamps
L7-L1, respectively. When switch 14 is pressed after the highest
static blood pressure level is generated (300 millimeters of mercury),
the power switch 26 is turned off. Most significant output line
67 from counter 34 will go high after counter 34 counts to a binary
eight. Output line 67 is coupled through NOR gate 104 and inverter
106 to the reset input of gate 60 in flip flop 25. This causes Q
output of flip flop 25 to go high thereby turning off transistor
Q1 and removing power from the circuit components. The next activation
of switch 14 turns on the device 10 and begins an identical cycle
as just previously described.
According to another feature of this invention, power switch 26
will also be disabled if selector switch 14 is not pressed within
a predetermined time period. This is accomplished by auto timer
circuitry 48 which includes a binary counter 108 similar to counter
100. The clock input to counter 108 is coupled to an output of counter
100 which provides clock signals at about a 30 Hertz rate. After
a predetermined time period, in this example about five minutes,
output line 110 of counter 108 will go high. This signal is coupled
to another input of NOR gate 104 and to the reset input of flip
flop 25 through inverter 106. Counter 108 is reinitialized or reset
whenever push button switch 14 is pressed. This causes counter 108
to begin counting all over again. The resetting of counter 108 is
accomplished by logic gating and control circuitry 32. When gate
66 goes low momentarily from switch 14 activation, inverter 112
provides a logical one signal over line 114 which is coupled to
the reset input of counter 108.
According to still another aspect of this invention, circuitry
28 is provided for monitoring the power level of battery 24 and
generating a visual indication when the battery power level has
fallen below a certain reference level. In this particular embodiment,
the reference level is about 2.5 volts. This is developed by a voltage
reference device 120 such as that manufactured by Analog Devices
and known as a 2.5 volt reference device. The output of device 120
is coupled to the inverting input of comparator 122. Resistors R13
and R14 provide a resistor divider network such that when battery
24 develops about 5.5 volts, the node between resistors R13 and
R14 will be about 2.5 volts. This node is coupled to the noninverting
input of comparator 122. The output of comparator 122 is coupled
to LED L10 through inverter 124. Thus, when the actual voltage level
from battery 24 falls below about 5.5 volts, LED L10 will be energized
to alert the user of the low battery level.
While this invention has been described in connection with particular
examples thereof, no limitation is intended thereby except as defined
in the appended claims. |