GB2260196A - Activity monitoring system - Google Patents

Abstract

A self-contained unit, worn on a human's or animal's body, contains a mercury tilt switch 1 which generates electrical signals in response to movement. These signals are accumulated by a counter 2, controlled by a timer 3. Accumulated counts are transferred to addresses in a random access memory during predetermined sampling intervals of 1 to 4 minutes. Overwriting of memory addresses whose capacity is exceeded by the accumulated count is prevented by a module 5, which stabilises the address at its maximum value. Overwriting of the first memory address when all addresses have received data, is prevented by a module 6. When the battery 7 becomes depleted a module 8 inactivates the device, preventing further recording of data and maintaining data recorded, using residual battery power. The system can transfer data by cable (10), electromagnetic induction, infra-red light, radio telemetry, and removable memory cards to an expansion board 11 in a computer(12). <IMAGE>

Description

ACTIVITY MONITORING SYSTEM This invention relates to a system for recording a person's physical activity and transferring the recorded data to a computer.

In medicine and studies of human activity many attempts have been made to obtain accurate information on physical mobility or functional capacity. These include questionnaires on activities which subjects undertake, laboratory based measurements such as treadmills, or ambulatory motion sensing devices.

Questionnaires are well established but essentially subjective, laboratory based measures are disruptive to the subject and not always applicable to certain types of subject, and most types of motion sensing device are inaccurate or unreliable.

According to the present invention there is provided a mercury tilt switch which is sensitive to changes of orientation, and integrated electronic circuits which count the signals from the mercury tilt switch, apply a time-base, and record the accumulated counts in random access memory. Essential parts of the system are an expansion board for a computer, and a specially written software module which enables data from the movement sensing device to be transferred to the computer's data storage system. The invention can also be used to measure animal activity, for which current methods cannot be employed.

Counts are accumulated during a predetermined sampling interval, typically between one and four minutes. At the end of each sampling interval, the accumulated count is transferred to a memory address, the counter zeroed, and the counting process repeated. In addition, security of data is provided by a) preventing the overwriting of the monitor's memory if its capacity is exceeded, and b) ensuring that data are not lost as the power supply is depleted.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which Figure 1 shows the relationships between the main components of the monitoring device. Figure 2 shows the organisation of the interface with the computer.

Referring to the drawing the monitor comprises a mercury tilt switch 1 connected to a counter circuit 2. The counter interacts with a timing circuit 3, such that at the end of a predetermined sampling interval the number of pulses counted is transferred to an address in the memory 4.

Computer memory behaves such that if its maximum capacity is reached it then "rolls over", that is the memory address returns to zero and only the balance of the value being written is stored. To prevent this, additional modules 5 and 6 detect the point when the maximum value is reached in a particular address (5) and when all addresses contain values (6). In the case of a full address, that address is "frozen", preventing overwriting, and in the case of all addresses being used, all further writing of data to the memory is halted. An additional electronic module 8 measures the voltage of the battery 7, and when this falls to a predetermined level, all further recording of data is halted. The memory is maintained by the residual battery power, as maintaining data requires less power than reading or writing data.

Although connections are not shown in Figure 1 for the sake of clarity, the battery 7 powers all modules of the device. The monitor device as shown in Figure 1 is self-contained with its own power supply 7, which may be rechargeable, and capable of attachment by a strap to a subject's body to record movement. Communication with the computer is achieved via a connector 9, which may be a parallel or serial interface, or alternatively an infra-red, inductive or radio link, or by a removable memory card.

To read data from the monitor requires a computer fitted with a special expansion board as shown in Figure 2. When data are to be transferred, the monitor's connector 9 is connected by a cable 10 to the expansion board 11, the latter being fitted into the computer 12.

Special programs enable the expansion board 11 to communicate with the monitor unit's memory 4, and provide the following functions: 1. Connect monitor and log on 2. Read monitor data to file 3. Print disk file 4. Clear monitor and enter patient data 5. Date stamp and start monitor 6. Quit this program Option 1 prompts the user to connect the monitor unit to the computer via the cable.

Option 2 prompts the user to enter a name for the data file to be transferred. Data are then copied from the monitor's memory to the computer's hard disk, under the file name entered by the user The software searches for "header information"(see Option 4 below) to ensure that communication between the computer and the monitor unit is intact.

Option 3 enables the data stored on the computer's hard disk to be displayed on the screen or printed on paper.

Option 4 clears the monitor's memory and prompts the user to enter identification data which are stored in the monitor's memory. For instance, a patient number could be entered into the monitor's memory to ensure that the data file is assigned to the correct patient. This is termed "header information".

Option 5 prompts the user to transfer the computer's system date and time to the monitor's memory, thus clearly marking the beginning of the recording period. As in Option 2 above, the software searches for header information and reports if none is found. When the date and time are recorded on the monitor, the movement recording process begins, and the monitor is disconnected and attached to the patient.

Option 6 returns the user to the computer's operating system level.

As an indication that the monitor unit is operating, a small light emitting diode (LED) 13, flashes whenever the memory is active. Therefore, when the memory is copied to the computer, or cleared (Options 2 and 4 above), the LED flashes for several seconds, and when a movement count is written to a memory address the LED flashes briefly. Thus, if for example the monitor's sampling interval has been set to two minutes, the LED will flash every two minutes thereafter.

The system as described herein can be adapted to operate in any of the following fashions: 1. Data transfer may be via serial or parallel interfaces 2. Data transfer may use a cable, an inductive loop, infra-red light, radio telemetry, or removable memory cards 3. The software menu items can be adapted to the needs of a particular user; monitor units can be initialised using the computer, and issued to remote sites in inactive mode, to be activated when applied to patients.

4. Some computers do not require on expansion board and transfer of data may be achieved using the computer's existing configuration, in conjunction with a modified program.

Data format provided is ASCII (American Standard Code for Information Interchange).

Claims (6)

1. System for electronically recording human or animal physical activity using a mercury tilt switch, counting and timing circuits, and electronic random access memory, and which can ensure preservation of data when its power supply is depleted to a predetermined level.

2. An activity monitoring system as claimed in Claim 1 having means by which, if activity data recorded reach the intrinsic maximum value of a memory address in the monitor device, any maximum values thus stored are retained and not overwritten.

3 An activity monitoring system as claimed in Claim 1 having means by which when activity data recorded fill all available memory addresses, overwriting of memory addresses is prevented and all data recorded are preserved.

4. An activity monitoring system as claimed in Claims 1 and 2 which can record movement data during a series of predetermined sampling intervals, and provide a record of levels of activity over a period of days or weeks.

5. An activity monitoring system as claimed in Claim 4 which can transfer data at intervals from the monitor unit worn by a human or animal subject to a computer, using special components and programs in the computer, and data transfer media including cables, electromagnetic induction, infra-red light, radio telemetry, and removable memory cards.

6. An activity monitoring system substantially as described herein with reference to figures 1-2 of the accompanying drawing.