Muscle testing apparatus

Apparatus for testing the strengths of muscle and muscle groups of a person. In use, an inflated pressure pad is engaged with a body area, and a force from a muscle or muscle group is applied to the pad. This force is sensed and a signal representing that force is displayed. The pressure pad is connected to the guide so that the pad may be fixed in a multitude of different positions to engage many different body areas subjected to forces from a multitude of different muscles and muscle groups.

BACKGROUND OF THE INVENTION 
This invention generally relates to apparatus for testing and indicating 
the strengths of muscles; and, more specifically, to apparatus especially 
well-suited to test and indicate the strengths of individual muscles. 
Recently, equipment has been developed to objectively and quantitatively 
measure the strength of individual muscles. As a therapeutic tool, such 
devices are very helpful in that they help a therapist identify specific 
muscles that need to be strengthened and to design a program that will 
help those particular muscles. Moreover, a quantitative measurement will 
tell not only which muscles are weak, but also how weak those muscles are. 
Further, as a person is undergoing treatment, an objective measure of the 
progress he or she is making, first, helps the therapist modify the 
treatment program, if necessary, and second, allows the patient to witness 
personally the fact that his or her muscles are getting stronger with 
therapy, which often encourages the patient to continue the treatment. In 
addition, often a patient may believe he or she is fully recovered and 
will discontinue treatment. An accurate, quantitative and objective 
measure of the strength of each muscle may show otherwise, however, and 
convince the patient to continue treatment. 
As an exercise training tool, an objective and quantitative measurement of 
the strength of individual muscles will help a person or a trainer develop 
a highly personalized exercise program that concentrates on the muscles 
that need the most work. Occasional retesting will enable an individual to 
observe personally the progress he or she is making, and will help show 
how effective a particular exercise program is and, if it becomes 
advisable to do so, how a program should be modified. An individual may 
test and record the strengths of his or her muscles while healthy to 
provide a personal standard; and if that person is later injured, he or 
she, while recovering, can compare his or her muscle strengths against 
that recorded standard to determine whether the muscles have adequately 
recovered before resuming a particular activity, thus lessening the risk 
of a re-injury or of a new injury. 
Prior art devices for testing and indicating the strengths of individual 
muscles are somewhat cumbersome to use. To elaborate, these devices are 
normally changed from one position to another to test different muscles, 
but usually kept in a fixed position while any one particular muscle is 
being tested. With prior art devices, it is sometimes difficult and time 
consuming to position the device properly to test some muscles; and, while 
testing certain muscles, it is likewise occasionally difficult to keep the 
device in the desired, fixed position. Indeed, because of these 
difficulties, prior art devices are, as a practical matter, not effective 
to test certain muscles. 
Moreover, prior art devices provide an indication of the force being 
developed by a particular muscle at a given instant in time, and this 
gives information about the strength of the muscle. While this is useful 
information, having an objective and quantitative indication of the 
strength and endurance of a muscle over a period of time such as 30 or 40 
seconds, would normally be much more helpful to a trainer or a therapist. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a muscle testing apparatus 
that is very simple to move between a multitude of different positions to 
test the strengths of different muscles and muscle groups, and yet is easy 
to hold rigidly in each of those positions. 
Another object of this invention is to provide a muscle testing apparatus 
with a pressure sensing pad that may be moved between and securely held in 
a multitude of different positions to engage many different muscles and 
muscle groups; and where, for each of these positions, a face of the pad 
may be located at least substantially perpendicular to the direction of 
the force developed by the muscle or muscle group being tested. 
A further object of the present invention is to provide a muscle testing 
apparatus that produces an objective and quantitative indication of the 
amount of force developed by a muscle over a period of time. 
These other objectives are attained with apparatus for testing the strength 
of muscles and muscle groups of a person, and comprising a guide means, an 
inflatable pressure pad, sensing and display means, and connecting means. 
The pressure pad is provided to engage body areas of a person subjected to 
forces from his or her muscles and muscle groups, and the sensing and 
display means is connected to the pressure pad to sense the force applied 
thereto and to display a signal representing that force. The connecting 
means connects the pressure pad to the guide means, and is adjustable 
between locked and unlocked positions. In the locked position, the 
connecting means securely holds the pressure pad in a fixed position 
relative to the guide means; and in the unlocked position, the connecting 
means supports the pressure pad for movement along the guide means, and 
pivotal movement about a horizontal axis. With this maneuverability, it is 
very easy to position the pressure pad at a multitude of locations to 
engage many different body areas subjected to forces from a multitude of 
different muscles and muscle groups. 
Preferably, the sensing and display means includes a pressure transducer, a 
variable capacitance oscillator, a pulse counter, counter control means, 
and display means. The transducer generates an electric current 
proportional to the extent to which the pressure on the pad exceeds a 
threshold pressure, and the variable capacitance oscillator generates 
electric current pulses at a variable frequency dependent on the magnitude 
of the current generated by the transducer. The pulse counter counts the 
electric pulse signals generated by the oscillator, the counter control 
means controls the counter to count only those pulses from the oscillator 
that are generated during a test period, and the display means displays 
the number of pulse signals counted by the counter during a test period. 
Preferably, the muscle and testing apparatus further includes a pump to 
pressurize the pressure pad, and a pump control circuit may be provided to 
activate the pump and to deactivate the pump automatically when the 
pressure in the pad reaches a preset level. 
Further benefits and advantages of the invention will become apparent from 
a consideration of the following detailed description given with reference 
to the accompanying drawings, which specify and show preferred embodiments 
of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate muscle testing apparatus 100 generally comprising 
guide means 102, pressure pad 104, sensng and display means 106, and 
connecting means 110. Preferably, with reference to FIG. 3, sensing and 
display means 106 includes pressure transducer 112, variable capacitance 
oscillator 114, counter 116, counter control means 120, and display means 
122. With reference to FIGS. 1, 2 and 4-6, connecting means 110 includes 
slide assembly 124, means 126 connecting that assembly to guide means 102, 
support arm 130, and means 132 connecting that arm to the slide assembly. 
Guide means 102 is provided to guide movement of pressure pad 104 along a 
predefined path, and for example the guide means may comprise a vertically 
extending post. In use, guide means 102 itself may be supported in any 
acceptable way. For instance, first bracket 134 may securely connect a 
lower end of guide means 102 to a floor or a wall, and second bracket 136 
may securely connect an upper end of the guide means to that wall or to a 
ceiling. Guide means 102 and brackets 134 and 136 may be made from 
numerous materials, and may have a variety of shapes and sizes, although 
preferably the guide means has a non circular horizontal cross-section to 
help prevent slide assembly 124 from pivoting or swinging around the guide 
means. The embodiment of guide means 102 shown in FIGS. 1 and 2 is made 
from aluminum and has a hollow, rectangular horizontal cross-sectional 
shape. 
Pressure pad 104 is provided to engage body areas of a person subjected to 
forces from his or her muscles and muscle groups. With reference to FIGS. 
1, 2 and 7, preferably, pad 104 comprises an inflatable flexible bag 
having a generally flat rectangular shape, forming front and back 
generally planar front and back faces. Pad 104 may be made from any 
suitable material such as rubber; and with a preferred embodiment, a flat 
strip 140 of hook and snap type fasteners, such as velcro, is connected to 
the back face of the pressure pad to hold the pad in place in apparatus 
100, in a manner discussed in detail below. In use, pad 104 is filled with 
a gas, such as ambient air, to a preset pressure. 
Sensing and display means 106 is connected to pressure pad 104 to sense the 
force applied to that pad and to generate a signal providing a 
quantitative measure of that force. With the preferred sensing and display 
means 106 illustrated in FIG. 3, pressure transducer 112 is connected to 
pressure pad 104 via line 142 (shown in FIGS. 1 and 2) so that the 
pressure on the transducer is equal to the pressure in the pressure pad, 
and the transducer generates an electric current proportional to the 
extent to which the pressure on the transducer exceeds a threshold 
pressure. 
Variable capacitance oscillator 114 is connected to transducer 112 to 
receive the current generated thereby, and the oscillator generates an 
electric current pulse at a variable frequency dependent on the magnitude 
of the current conducted to the oscillator. In particular, the frequency 
of this current pulse increases and decreases, although not necessarily 
linearly, with the magnitude of the current generated by the transducer 
112. 
Counter 116 is connected to variable capacitance oscillator 114 to count 
the electric pulse signals generated by the oscillator. More specifically, 
counter 116 is an electronic device having a multitude of states; and each 
time the counter receives an electric current pulse from oscillator 114, 
the counter changes from one state to the next. Hence, up to the maximum 
capacity of the counter, the state of the counter indicates the number of 
pulses that have been conducted to the counter. The output of counter 116 
is an electric current dependent on the state of the counter, and thus 
that electric current is also indicative of the number of pulses that have 
been conducted to the counter. 
Counter control means 120, described in detail below, is connected to and 
controls counter 116 to count only those pulses from oscillator 114 that 
are generated during a test period. In this way, the number of pulses 
counted by counter 116 provides a quantitative and objective indication of 
the amount of force applied to pressure pad 104 over that test period. 
Display means 122 is connected to counter 116 to display the number of the 
electric pulse signal generated by variable capacitance oscillator 114 
during a test period. Display means 122 receives the output signal from 
counter 116 and converts that output signal into one or more electric 
signal that are used to show a number that is equal to the number of pulse 
signals generated by oscillator 114. This number may be shown in a variety 
of different ways; and, for example, display means 122 may comprise a four 
character display board, with each character comprised of seven LED 
segments, designed to show the numbers 0 to 9999. 
Pressures transducers, variable capacitance oscillators, pulse counters, 
and display means of the above-described types are all well-known devices. 
Any suitable devices of these types may be used to practice the present 
invention, and it is unnecessary to explain the details of these 
components further herein. Moreover, the various elements of sensing and 
display means 106 may be located in or connected to a protective housing 
144, which in turn may be mounted on top bracket 136. 
With reference again to FIGS. 1 and 2, connecting means 110 connects 
pressure pad 104 to guide means 102, and this connecting means is 
adjustable between locked and unlocked positions. In the locked position, 
connecting means 110 securely holds pressure pad 104 in a fixed position 
relative to guide means 102; and when connecting means 110 is in the 
unlocked position, pressure pad 104 is slideable along the guide means 
102, and pivotally movable about a horizontal axis. With this mobility and 
maneuverability, pressure pad 104 may be easily adjusted between and 
securely held in a multitude of different positions, in which the pressure 
pad may be readily engaged by many different body areas to test the 
strengths of a multitude of different muscles and muscle groups. Moreover, 
for each of these positions of pressure pad 104, the front face thereof 
may be located at least substantially perpendicular to the direction of 
the force developed by the muscle or muscle group being tested. 
As is believed best shown in FIGS. 4-6, slide assembly 124 of connecting 
means 110 is mounted on guide means 102, and preferably the slide assembly 
includes front plate 146 and U-shaped bracket 150 connected together to 
form a hollow enclosure extending around the outside of guide means 102. 
Connecting means 126 connects slide assembly 124 to guide means 102; and 
this connecting means 126 has a locked position securely holding slide 
assembly 124 in a fixed position on guide means 102, and an unlocked 
position wherein the slide assembly is slideable along the guide means. 
Preferably, this connecting means 126 comprises pressure plate 152, 
threaded pin 154, and handle 156. Plate 152 is located inside slide 
assembly 124, between the slide assembly and the back side of guide means 
102, and the pressure plate is supported for movement toward and away from 
that guide means. For example, a plurality of guide pins 158 may be 
connected to pressure plate 152 and extend into bores in slide assembly 
124 to support the pressure plate for movement toward and away from guide 
means 102. 
Pin 154 is threaded through a threaded bore 160 in slide assembly 124, 
rearward of pressure plate 152. Pin 154 extends rearward of slide assembly 
124, and handle 156 is securely mounted on this rearward end of the 
threaded pin. To lock slide assembly 124 to guide means 102, handle 156 
and pin 154 are turned so that the pin advances in bore 160 and pushes 
plate 152 into a tight, secure pressure engagement with guide means 102, 
holding the entire assembly 124 rigidly in place. To unlock slide assembly 
124, handle 156 and pin 154 are turned so that pin moves rearward in bore 
160, releasing plate 152 from the pressure engagement with guide means 
102, and allowing the slide assembly to slide along the guide means. 
Support arm 130 extends away from slide assembly 124; and preferably, 
support arm 130 includes first and second legs 162 and 164, and sleeve 
166. Legs 162 and 164 are connected together to form an L-shaped bracket, 
with the former leg located immediately forward of slide assembly 124, and 
with the latter leg extending outward from leg 162, substantially 
perpendicular thereto. Sleeve 166 extends around and is tightly fitted on 
leg 164, and thus forms front and rear faces; and flat, rectangular strips 
170 of hook and snap type fasteners are secured to these faces of sleeve 
166. Pressure pad 104 may be connected, by means of its own fastener strip 
140, to either of strips 170, and thus may be located on either side of 
leg 164. 
Connecting means 132 connects support arm 130 to slide assembly 124, and 
this connecting means 132 also has locked and unlocked positions. In its 
locked position, connecting means 132 securely holds support arm 130 in a 
fixed position relative to slide assembly 124; and in its unlocked 
position, connecting means 132 supports arm 130 for pivotal movement about 
a horizontal axis. This connecting means 132 preferably includes threaded 
screw 172 and clamping means 174. Slide assembly 124 forms a front 
central, through opening 174, leg 162 of support arm 130 forms an aligned 
opening, and screw 172 extends through these aligned openings. The head of 
screw 172 abuts against an inside surface of slide assembly 124 to hold 
the screw against forward movement, and clamping means 174 is threadably 
mounted on the forward end of screw 172, forward of leg 162. 
To lock support arm 130 to slide assembly 124, clamping means 174 is 
rotated to move i rearward on screw 172 (toward guide means 102) to 
securely and tightly clamp leg 162 against the slide assembly. To unlock 
support arm 130 from slide assembly 124, clamping means 174 is rotated to 
move it forward on screw 172 (away from guide means 102) to release leg 
162 from the pressure engagement against the slide assembly. In this 
unlocked position, screw 172 still supports arm 130, and the arm may be 
pivoted about the axis of the screw. 
Clamping means 174 preferably comprises threaded socket 176 mounted on 
screw 172, and handle 180 mounted on that socket. Handle 180 may be 
mounted on socket by means of a pawl and a ratchet wheel so that the 
handle may be used to rotate the socket around screw 172 without requiring 
full rotation of the handle itself. A washer may be located between socket 
176 and leg 162, and a clutch plate may be located between that leg and 
slide assembly 124. 
With a preferred embodiment of the invention, disk 182 and pins 184 may be 
used to help support arm 130 when connecting means 132 is in its unlocked 
position. To elaborate, plate 146 of slide assembly 124 forms a front 
circular opening, and disk 182 is located in this opening in a close, but 
movable, fit with the surfaces forming the opening so that the disk is 
rotatable within the opening about the axis of the disc. Disk 182 forms 
the central opening 174 of slide assembly 124, and this disk also forms a 
central recess at the end of that bore. The head of screw 172 seats in 
this recess, and the screw head causes the disk and the screw to rotate 
together about their common axis. Pins 184 are connected to leg 162 and 
extend therefrom into aligned sockets or openings in disk 182, and hence 
help support arm 130. Pins 184, of course, rotate with disk 182 and thus 
do not restrict pivotal movement of support arm 130. Preferably, plate 146 
of slide assembly 124 includes a shoulder located directly forward of the 
outside portion of disk 182 to hold the disk against forward movement 
Preferably, apparatus 100 further includes a pump 186, schematically shown 
in FIG. 8, to pressurize pressure pad 104 More specifically, pump 186 is 
connected to the interior of pad 104 via line 190 to conduct pressurized 
air into the interior of the pad. This may be done occasionally, for 
example at the start of a day, to replace any air that might have escaped 
from the pressure pad 104 and to bring the pressure inside the pad to a 
preset or standard level. Any suitable pump may be used to do this, and 
the pump may also be located inside display housing 144. A one way check 
valve 192 may be located in line 190 to inhibit air from escaping from pad 
104 through line 190. Preferably, pump 186 is electrically operated, and 
one electrical control circuit for the pump is described in detail below. 
To prepare apparatus 100 for operation, guide means 102 is secured in place 
via brackets 134 and 136, and pump 186 may be used to bring the pressure 
in pad 104 to a desired level. To test a particular muscle or muscle group 
of a subject, the subject stands or sits next to apparatus 100, and 
pressure pad 104 is positioned so that it may be engaged by a body area 
that may be moved by that particular muscle or muscle group, with the 
front face of the pressure pad face perpendicular to the direction of the 
force developed by the muscle or muscle group. It is believed that best 
results are obtained if pad 104 is located at the middle of the arc, or 
range of motion, through which the body area would normally move as a 
result of the force applied to the body area by the muscle or muscle group 
being tested. 
Pressure pad 104 is located in this particular position by locking slide 
assembly 124 at a selected height, and locking support arm 130 at a 
selected angle relative to the vertical. An operator may wish to record 
this selected height and angle; and guide means 102, slide assembly 124 
and support arm 130 are provided with markings to indicate these 
measurements. Also, a graph or chart may be located on the floor adjacent 
apparatus 100 so that the operator can record the subject's position 
relative to the apparatus. In addition, it is desirable to position the 
subject and pad 104 to isolate the muscle or muscle group being tested; 
that is, to position the subject and the pressure pad so that only forces 
developed by the muscle or muscle group being tested are applied to the 
pressure pad. To accomplish this, when testing certain muscles or muscle 
groups, it may be preferred to have the patient sit in a chair with his or 
her legs raised off the ground or floor. 
The subject then engages pad 104 with the body area. At the start of a test 
period, the subject flexes the muscle or muscle group under study to apply 
a force to pressure pad 104, and the subject continues to apply this force 
to the pressure pad until the end of the test period. The magnitude of the 
force applied to pressure pad 104 is sensed by sensing and display means 
106, which produces a quantitative signal representing that force, and in 
particular, a quantitative signal representing the amount of the force 
applied to pressure pad 104 over the test period, which indicates the 
endurance of the muscle being tested. The results of the test may then be 
recorded and compared with the results of other tests to provide a 
quantitative comparison of changes in a patient's muscle or muscle group. 
For example, the test results may show that a particular muscle has become 
stronger as a result of an exercise program. 
FIGS. 9a-9g illustrate seven application of muscle testing apparatus 100; 
and in particular, these figures show subject 200 and seven different 
positions of pressure pad 104 to test seven different muscle or muscle 
groups of the subject. FIG. 7a shows the positions of pad 104 and subject 
200 to test the deltoid muscle; FIG. 7b, the trapezius and rhomboideus 
muscles; FIG. 7c, the pectoral major muscle; and FIG. 7d, the bicep 
muscle. FIG. 7e shows the position of pad 104 and subject 200 to test the 
ankle dorsi flexors muscle; FIG. 7f, the hamstring muscle; and FIG. 7g, 
the quadriceps muscle. 
In one clinical program, apparatus 100 was used to test the 
above-identified seven muscle groups on twenty-three adult men and women. 
The ages of the subjects were between 21 and 60 years, with their mean age 
being 29.6 years. The subjects were all right handed, had not been under 
the care of a physician for at least the previous six months, and reported 
no medical complaints. During each testing session, four tests were 
conducted for each of the seven positions. The test period for two of 
these four tests was set at five seconds, the test period for the other 
two tests was set at ten seconds, and a one minute rest period was given 
between each test. Each subject underwent two testing sessions, with the 
first one followed seven to nine days later by the second session. 
Pearson product moment correlations were used to evaluate reliability of 
the test scores for each of the seven positions. Reliability was assessed 
within a session (test 1 versus test 2 at the same test period) and 
between sessions (e.g. test 1 of session 1 versus test 1 of session 2). 
Within session reliability coefficients were very high, and the median 
value was 0.97 with only one coefficient out of 28 below a value of 0.90. 
Between-session reliability was also very good with most coefficients 
ranging between 0.79 and 0.92 (median=0.87). The one position at which the 
between-session reliability was lower was for ankle flexors, which had a 
median value of 0.65. 
These data show that the apparatus of this invention provides highly 
reliable measures of six of the seven tested muscles and muscle groups, 
and it is believed that even this may be improved as the testing 
procedures are refined. These studies clearly show that the present 
invention may be effectively employed as a valuable tool in health and 
rehabilitation settings. 
Apparatus 100 is relatively simple to build and operate, and it is very 
easy for both the operator and the patient to understand and conduct the 
above-described testing procedures. The test results are immediately 
available, and are easy to read, understand and interpret. The test 
results are objective and consistent, minimizing human variables and other 
subjective factors that are inherent in manual muscle testing procedures. 
Because the test results are objective and consistent, they help an 
operator determine the accuracy of subjective complaints from a patient, 
and they help to diagnose basic problems. For instance, the test results 
show quantitatively how weak different muscles are, and help to 
distinguish between muscle weaknesses caused by nerve damage from muscle 
weaknesses caused by strain. 
Control means 120 for counter 116 preferably comprises electric control 
circuit 300 shown in FIG. 10. Generally circuit 300 includes NOR gate 302 
and timer means 304; and preferably the counter control circuit further 
includes means such as switch section 306 to select the length of the time 
period, and signal means 310 to indicate the end of a test period. With 
the embodiment of circuit 300 shown in FIG. 10, timer means 304 includes 
start switch 312, NOR gate 314, clock 316, up-counter 320, and test time 
comparator 322, and signal means 310 includes AND gate 324, pulse 
generator 326, and buzzer 330. 
NOR gates and AND gates are electronic logic devices having two input 
connections and one output connection, and their operations are summarized 
in FIG. 11. The output connection of of a NOR gate has a high voltage 
potential only when both input connections are at a low voltage potential; 
and, otherwise, the output of the NOR gate is at a low voltage potential. 
The output connection of an AND gate has a high voltage level only when 
both input connections of the gate are at a high voltage level, and 
otherwise the output of an AND gate is at a low voltage level. 
First and second input connections 302a and 302b of the NOR gate 302 are 
connected to the output of oscillator 114 and to the output of timer means 
304 respectively, and output connection 302c of the NOR gate is connected 
to counter 116. During a test period, timer means 304 conducts a low 
voltage potential to input connection 302b of NOR gate 302; and at the end 
of the test period, the timer means 304 conducts a high voltage signal to 
input connection 302b. In this way, with reference to FIG. 11, during a 
test period, when no electric pulse is being conducted to NOR gate input 
connection 302a from oscillator 114, the output connection 302c of the NOR 
gate is at a high voltage potential, and that potential drops to a low 
voltage potential when an electric pulse is conducted to input connection 
302a. Output connection 302c remains at that low voltage potential as long 
as the pulse is conducted to input connection 302a; and, once that pulse 
ends, output connection 302c of NOR gate 302 returns to a high voltage 
potential. Each time output connection 302c changes from a low voltage 
potential to a high voltage potential, a new current is conducted to and 
counted by counter 116. Thus, the count kept by counter 116 increases by 
one at the end of each pulse generated by oscillator 114. 
With the embodiment of timer means 304 shown in FIG. 10, between test 
periods, the output connection of test time comparator 322 is maintained 
at a high voltage level; and this output connection is connected to input 
connection 314b of NOR gate 314, maintaining that input connection at a 
high voltage level between test periods. As a result of this, NOR gate 
output connection 314c is kept at a low voltage level between test 
periods. To start a test period, start switch 312 is temporarily closed to 
generate a high voltage signal, and then re-opened to return the start 
switch output to a low voltage level. This temporary high voltage signal 
is conducted both to input connection 314a of NOR gate and to comparator 
322, and this signal to the comparator resets that device so that the 
output thereof returns to a low voltage level. When this happens, input 
connection 314b of NOR gate 314 also falls to a low voltage level; and 
thus when start switch 312 is re-opened, both input connections 314a and 
314b of NOR gate 314 are at a low voltage level. 
This causes NOR gate output connection 314c to change to a high voltage 
level, and this activates clock 316. Clock 316 then generates current 
pulses at a regular frequency, and these pulses are conducted to 
up-counter 320. Counter 320 generates a continuous output current the 
magnitude of which depends on the number of pulses received from clock 316 
since the last time the up-counter was reset. Hence, the magnitude of the 
current generated by up-counter 320 increases over a test period. 
Test time comparator 322 is a conventional multi-plex chip, a first input 
of the comparator is connected to up-counter 320, and an output of the 
comparator is connected to input connection 302b of NOR gate 302. 
Comparator 322 receives the output current from up-counter 320 and 
compares the magnitude of that current to a preset current level. As long 
as the magnitude of the current from up-counter 320 is below the preset 
level, the output connection of comparator 322 is at a low voltage level. 
However, when the current from up-counter 320 exceeds the preset level, 
the output of comparator 322 switches to a high voltage level. This 
voltage level is conducted to NOR gate input connection 302b so that the 
voltage level of NOR gate output connection 302c changes to or remains at 
a low voltage level, and no further current pulses are conducted to 
counter 116. At this time, the number shown on display means 122 is then 
equal to the number of pulses generated by oscillator during the test 
period. The high voltage signal from comparator 326 is also conducted to 
NOR gate input connection 314b, causing output connection 314c of NOR gate 
314 to change to a low voltage level, deactivating clock 316. 
The output of comparator 322 remains at a high voltage level until it is 
reset, and this voltage signal both prevents NOR gate 302 from passing any 
further pulses to counter 116 and maintains clock 316 deactivated until 
the start of the next test period. Preferably, start switch 312 is also 
connected to reset input connections on counter 116 and up-counter 320 so 
that when the start switch is closed, the counter and up-counter are all 
reset to zero or initial states. 
Switch section 306, including a plurality of switches 306a, 302b and 306c, 
may be provided to select the length of the test period. Each switch 306a, 
b and c is connected to comparator 322; and each switch has a high, or 
open, position (shown in FIG. 10) in which the switch conducts a high 
voltage signal to the comparator, and a low, or closed, position in which 
the switch conducts a low voltage signal to the comparator. 
Each switch 306a, b and c may represent a different length of time and, for 
example, switches 306a, b and c may represent ten, twenty and forty 
seconds, respectively. When switch 306a is in its low state, and switches 
302a, b and c are both in their high states, the test period is 10 
seconds; when switch 306b is in its low state, and switches 306a and c are 
both in their high states, the test period is twenty seconds; and when 
switch 306c is in its low state, and switches 306a and b are both in their 
high states, the test period is forty seconds. Moreover, switches 306a, b 
and c may be used in an accumulative manner so that when switches 306a and 
b are in their low states, and switch 306c is in its high state, the test 
period is thirty seconds; and when switches 306b and c are in their low 
states and switch 306a is in its high state, the test period is sixty 
seconds. 
Also, comparator 322 may be programmed so that the test period may be set 
to a seventh time length, such as five seconds, when all three switches 
306a, b and c are in their high states. Comparator might further be 
programmed so that the test period is set to an eight time length when all 
three switches 306a, b and c are in their low states; however, preferably, 
this position of switches 306a, b and c is used to help actuate pump 186, 
as discussed in detail below. Control circuit 300 may be provided with a 
series of display lights 332, connected to switch section 306, to indicate 
the test time period that has been selected by the operator. 
Clocks, up-counter, and multi-plex chips of the above-described types are 
all well known devices. Any suitable devices of these types may be used to 
practice the present invention, and it is unnecessary to explain the 
details of these components herein. Similarly, any suitable switches may 
be used as switches 306a, b and c and 312. Switches 306a, b and c may be 
single throw, double pole switches that will stay in either their state or 
their low states until manually changed. Preferably, switch 312 is a 
momentary switch, spring biased to an to an open position so that the 
switch must be forced to its closed position, and once released from that 
position, will automatically return to its open position. 
During its operation, display means 122 produces a high frequency current 
signal, and this current is principally employed to operate the display 
shown by the display means. With circuit 300, this high frequency current 
is also used in signal means 310 to indicate the end of a test period. 
More specifically, a first input connection 324a of AND gate 324 is 
connected to display means 122 to receive that high frequency current 
signal therefrom. A second input connection 324b of the AND gate is 
connected to pulse generator 326, and output connection 324c, of the AND 
gate 324 is connected to buzzer 330. 
Pulse generator 326 is connected to the output connection of test time 
comparator 322; and when that output connection changes from a low voltage 
level to a high voltage level, generator 326 generates one high voltage 
signal that lasts for about one second. Thus, during the duration of this 
one signal, the output connection 324c of AND gate 324 will alternate 
between high and low voltage levels in synchronization with the signal 
from display means 122. This alternating voltage level of output 
connection 324c causes an alternating current to pass through buzzer 330, 
generating an audible signal. 
FIG. 12 schematically shows electric control circuit 400 for pump 186. 
Generally, pump 186 is electrically located in line 402, between a DC 
voltage source and ground (not shown), and pump control circuit 400 
includes pump switch means 404 and switch control means 406. Switch 
control means 406 includes switch section 306, start switch 312, and NOR 
gate 302 discussed above in connection with counter control circuit 300; 
and the switch control means 406 further includes AND gate 410 and 
flip-flop 412. A diode 414 may be located in line 402 to keep the current 
passing through pump 186 below a preferred level. 
Switch 404 has a pair of main terminals and a gate or trigger terminal. In 
the absence of any applied voltages, switch 404 assumes an open condition 
in which a very high impedance exists between its main terminals to 
effectively constitute an open switch. However, when a voltage of 
appropriate magnitude is applied to the gate terminal, switch 404 changes 
to a closed state in which a very low impedance is presented between its 
main terminals so that it essentially functions as a closed switch. Once 
rendered conductive, switch 404 will remain in a closed or conductive 
state, until the gate current drops below a certain level, at which time 
the switch returns to its open or off state. Thereafter, conduction 
through switch 404 will not occur until a triggering current of sufficient 
magnitude is again applied to the gate. Any suitable electronic switch, 
may be employed in the practice of this invention. 
Switch control means 406 is electrically connected to the gate of switch 
means 404 to change that switch means between its open and closed states. 
A first input connection 410a of AND gate 410 is connected to switch 
section 306, a second input connection 410b of this AND gate is connected 
to the output connection 302c of NOR gate 302, and output connection 410c 
of the AND gate is connected to flip flop 412. Flip flops such as flip 
flop 412 of circuit 400, are electronic devices having a plurality of 
input connections and output connections and a number of characteristics. 
First, flip flops have a pair of output connections or signals that 
maintain an opposite relationship--when one of these output connections 
has a high voltage potential, the other output connection has a low 
voltage potential, and vise versa. Second, flip flops can be constructed 
so that, if certain input and output conditions exist, a change in the 
voltage level of only one of the input connections will have no affect on 
the voltage levels of the output connections of the flip-flop, and the 
voltage levels of output connections of such a flip-flop will remain fixed 
until the voltage levels of both input connections change. 
Only one of the output connections of flip-flop 412 is used in circuit 400, 
and this connection is connected to the gate of electronic switch 404. As 
previously mentioned, a first input connection 412a of flip-flop 412 is 
connected to output connection 410c of AND gate 410, and the second input 
connection 412b of the flip-flop is connected to start switch 312. FIG. 13 
summarizes the operation of flip-flop 412. When inputs connections 412a 
and b are at low voltage levels, output connection 412c is at a low 
voltage level, and that output remains at this voltage level until both 
input connections 412a and b change to high voltage levels. When this 
happens, output connection 412c changes to a high voltage level, and this 
output remains at this voltage level until both inputs connections 412a 
and b change to a low voltage level, at which time the output connection 
also changes to a low voltage level. 
To prepare circuit 400 to activate pump 186, switches 306a, b and c are all 
moved to their closed, or low, positions (shown in FIG. 12). Switch 
section 306 is designed so that, when these switches 306a, b and c are all 
closed, a high voltage level is developed at input connection 410a of AND 
gate 410. Then, start switch 312 is momentarily closed, and this causes a 
number of events to occur. First, 312 is closed, input connection 302b of 
NOR gate 302 is reset at a low voltage level. If, at this time, the 
pressure in pad 304 is below that at which transducer 112 generates a 
current, output connection 302c of NOR gate 302 and hence input connection 
410b and gate 410 both change to high voltage levels. When this happens, 
output connection 410c of AND gate 410 and input connection 412a of 
flip-flop 412 change to high voltage states. Second, when switch 312 is 
closed, a high voltage level is developed at flip-flop input connection 
412b; and this, in combination with the development of the high voltage 
level at flip-flop input connection 412a, causes a high voltage level to 
develop at flip-flop output connection 412c. This causes a current to be 
conducted to the gate of electronic switch 404, changing the switch to its 
closed state and actuating pump 186. 
As soon as start switch 312 returns to its open position, input connection 
412b of flip-flop 412 returns to a low voltage level. However, output 
connection 412c of flip-flop 412 remains at a high voltage level--and thus 
pump 186 remains activated--until both input connections 412a and b of the 
flip-flop fall to a low voltage level. As pump 186 operates, it increases 
the pressure in pad 104; and when a preset pressure is reached, transducer 
112 generates a current. This current causes oscillator 114 to generate a 
pulse, bringing input connection 302a of NOR gate 302 to a high voltage 
level. This, in turn, causes output connection 302c of NOR gate 302 and 
input connection 410b of AND gate 410 to change to low voltage levels. 
When this happens, input connection 412a of flip-flop 412 falls to a low 
voltage level, and this causes output connection 412c of flip-flop 412 
also to fall to a low voltage level, changing switch 404 to its open state 
and deactivating pump 186. 
Pump control circuit 400 may be provided with a blinking light 416 to 
indicate that pump 186 is operating. To elaborate, a first input 
connection 420a of AND gate 420 is connected to output connection 412c of 
flip-flop 412, a second input connection 420b of the AND gate is connected 
to clock 316, and output connection 420c of AND gate 420 is connected to 
light 416. As previously mentioned, when start switch 312 is closed, a 
current is current is conducted to clock 316 to activate that device to 
generate current pulses, and these pulses are conducted to AND gate input 
connection 420b. At the same time, when flip-flop output connection 412c 
is at a high voltage level, which is the case when pump 186 is operating, 
input connection 420a of gate 420 is held constant at a high voltage 
level. Hence, under these conditions, output connection 420c of AND gate 
420 changes between high and low voltage levels as input connection 420a 
changes between those levels, and consequently light 416 will blink in 
synchronization with the pulses from clock 316. 
As will be understood by those of ordinary skill in the art, any suitable 
voltage sources may be used as the voltage sources shown in the drawings; 
and these voltage sources may all be connected to one primary source, such 
as a DC battery pack. An on-off switch (not shown) may be located in 
series between that voltage source and circuits 300 and 400, and a light 
422 (shown in FIG. 12) may be provided to indicate whether that on-off 
switch is in its on or off position. In the case where the primary voltage 
source for pump 186 and circuits 300 and 400 is a DC battery pack, 
apparatus 100 may be provided with a battery charger that may be used to 
connect the battery pack to a conventional AC voltage source to charge the 
battery pack when apparatus 100 is not otherwise being used. Also, 
suitable energy sources (not shown) are provided for the electronic 
elements of circuits 300 and 400 including transducer 112, oscillator 14, 
counter 116, display 122, NOR gate 302, OR gate 314, clock 316, up-counter 
320, comparator 322, AND gates 344, 410 and 416, and flip-flop 412. 
While it is apparent that the invention disclosed herein is well calculated 
to fulfill the objects previously stated, it will be appreciated that 
numerous modifications and embodiments may be devised by those skilled in 
the art, and it is intended that the appended claims over all such 
modifications and embodiments as fall within the true spirit and scope of 
the present invention.