5 6
includes a column multiplexer 48 and row multiplexers sure sensor sheet 22 is disposed between the torso of 41-46. It should be appreciated that, while FIG. 1 patient 70 and the upper surface of bed 72. Sheet 22 is shows six multiplexers 41-46, it should be appreciated connected to microcomputer 30 by means of interface that, in this exemplary embodiment, there is a row mul- circuitry 74 that includes the row multiplexers 41-46 (or tiplexer provided for each column in the array. Each 5 such other number of row multiplexers as needed) as row multiplexer is operative to access each of the sen- well as column multiplexer 48. Further, interface cirsors in its column by row position. Thus, for example, cuitry 74 contains a power supply which produces a row multiplexer 41 accesses the sensors in column Ci so voltage signal which is modulated by each of pressure that the output of multiplexer 41 on line 51 corresponds sensors 20 proportionately to the force sensed thereby, to the row position of selected pressure sensor in col- 10 Interface circuitry 74 is connected to the array of presumn Cj. The selection of the row position for each of sure sensors by means of a cable harness 76 which is the columns is controlled by microcomputer 30 over electrically connected to the array of sensors by means command line 60. Thus, microcomputer 30 requests an of electrical connector 78. The command lines as well access to the selected row so that each of multiplexers as data line 64 are included within cable harness 80. 41-46 provides the pressure signal from the pressure 15 Keyboard input 32 may be used to command misensor having that row position in the specific column crocomputer 30 to execute a read event or otherwise to accessed by the respective row multiplexers 41-46. This program microcomputer 30 to automatically execute data is provided, then, on output lines 51-56 which one or more read events at a selected time or times. It respectively correspond to each of row multiplexers should be fully understood that the manner of executing 41-46. Thus, data lines 51-56 each carry a force signal 20 a read event and the order in which data is received corresponding to a set of pressure sensors in a given from each of pressure sensors 20 may be fully controlled row. by the programming of microcomputer 30. The force
A column multiplexer 48 is provided to multiplex profile of a read event may be displayed on display data lines 51-56 so as to select a specific data line 51-56 screen 34 or may be output in hard form by means of as commanded by microcomputer 30 over command 25 printer 38, all as is known in the art. line 62. Thus, a force signal may be presented on data FIG. 3 shows another example of use of pressure line 64. Pressure data on data line 64 accordingly corre- sensors 20 on sheet 22 wherein here sheet 22 is wrapped sponds to a specific pressure sensor in the array as con- around the lower portion of an arm 90 of a patient weartrolled by the row selected by multiplexers 41-46 and ing a cast 92. In FIG. 3 it may be appreciated that presthe column selected by multiplexer 48. Since pressure 30 sure sensors on sheet 22 monitor the pressure between sensors 20 are typically analog devices, the pressure the exterior surface of the forearm and cast 92 which data signal or force signal on data line 64 is an analog may change over time due to an increase or decrease in signal which is proportional to the pressure sensed by swelling or atrophy of the arm. This pressure can be each of sensors 20. This signal is supplied to an analog to monitored in order to determine any excess pressures digital converter 66 which then supplies a digital force 35 which may cause discomfort or injury to the patient, signal to microcomputer 30 by way of data line 68. With reference to FIGS. 2 and 3, it may be seen that
From the foregoing, it may now be seen that mi- pressure sensors 20 can be used to monitor the distribu
crocomputer 30 may receive from the array of pressure tion of weight of a bed ridden patient on a bed to idensensors 20 force signals corresponding to the force of tify any areas of excess pressure that might result in
pressure monitored by each of sensors 20 by executing 40 ulceration of the skin.
a "read event" which may be defined as a scan of the As noted above, this technique could also be used for
array of pressure sensors to derive a force profile corre- other articles of furniture such as wheel chairs and the
lated to the location of each pressure sensor and the like. These excess pressures can be used to generate a
respective force detected thereby. Here, for example, signal, for example, to notify nursing personnel of a
microcomputer 30 may command each of row multi- 45 need to redistribute the weight of the bed ridden person
plexers 41-46 to provide pressure data from the first or otherwise adjust the contour of the support surface,
row after which microcomputer 30 then commands The monitoring can be performed periodically, on demultiplexer 48 to supply the analog signal from each of mand, upon the occurrence of a selected event or at any
lines 51-56, consecutively. The microcomputer may other time within normal system design,
store this pressure information, digitilized by analog to 50 The present invention finds particular utility, as an
digital computer 66, in memory 38 with this data being aide in fitting prosthetic devices on stump portions of a
correlated to each sensor in row Ri. Microcomputer 30 limb. This pressure monitoring apparatus is shown in
may then command multiplexers 41-46 to supply data 'FIGS. 5-9 as it is used to fit an artificial leg, shown in
from row R.2 and again read this data by commanding FIG. 4. Turning, then, to FIG. 4, it may be seen that a
multiplexer 48 to read data on data lines 51-56. This 55 prior art artificial leg 100 includes a lower foot portion
process repeats for each row Ri-Rm. At the completion 101 having a heel portion 102, a ball portion 103 and a
of the read event, memory 36 has stored pressure data toe portion 104 at a distal end thereof. A socket portion
corresponding to each of the sensors as it existed at the 106 is located oppositely foot portion 101 and includes
time of the read event. This array of data thus comprises a socket 107 adapted to receive the distal end of leg
a force profile for the pressure distribution across the 60 stump 108 of the human body. A cushioning pad 109 is
array of sensors 20 on sheet 22. This data can be dis- located between the bottom wall of the socket and the
played in a variety of formats; the data may also be distal end portion of stump 108.
interpolated to give pressure estimates between sensor Monitoring the fit between the stump and the artific
locations. ial leg 100 is best shown in FIGS. 5 and 6. Here, it may
As shown in FIG. 2 this pressure monitoring appara- 65 be seen that the pressure monitoring apparatus includes
tus has advantages in monitoring the pressure between a interface circuitry 74 which may be contained in a hous
body part and a contact surface. In FIG. 2, it may be ing 75 that is strap mounted onto a portion of stump 108
seen that a patient 70 is reclining on a bed 72, and pres- by means of fastening strap 112. Wiring 121-126 inter
