Signal processing circuit

• US 3,897,774 A
• Filed: 01/28/1974
• Issued: 08/05/1975
• Est. Priority Date: 01/28/1974
• Status: Expired due to Term

• Current Assignee: Richard A. Johnson, Thomas H. Burdick
• Original Assignee: Richard A. Johnson, Thomas H. Burdick
• Inventors: Burdick, Thomas H., Johnson, Richard A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/437,110
• Time in Patent Office: 554 Days
• Field of Search: 128/2.5R,2.6A,2.6B,2.6R,419PT 328/139,114,151 307/267,263,238,247R,251,231,239
• US Class Current: 600/510
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

A signal processing circuit for use in a digital memory-type EKG display system wherein analog EKG signals are periodically sampled and converted to a digital signal for processing and display comprises an amplitude hold circuit which maintains the instantaneous amplitude of pacemaker pulses contained in the analog EKG signal constant for a sufficient period of time to insure recognition of the pulses in the next sampling. Because no access is required to the sampling or conversion circuits of the system, the processing circuit can be readily added to an existing system.

Claims

1. A signal processing circuit for use in conjunction with a data collection system wherein an analog input signal is sampled at periodic spaced time intervals and applied to an analog-todigital converter to develop a digital output signal for causing said system to respond to a transient pulse appearing in said analog input signal between said periodic samplings, said signal processing circuit comprising, in combination:

pulse discrimination means for producing a control signal in response to the occurrence of said transient pulse; and

means including an amplitude hold circuit responsive to said control signal for maintaining the instantaneous level of said analog input signal as applied to said analog-to-digital converter constant for a predetermined hold period following the occurrence of said transient pulse such that the amplitude of said pulse is sampled by said converter and converted to a corresponding digital output signal.

2. A signal processing circuit as defined in claim 1 wherein said predetermined hold period is substantially equal to the sampling period of said data collection system.

3. A signal processing circuit as defined in claim 1 which further comprises a multivibrator responsive to said control signal for conditioning said amplitude hold circuit operative for said predetermined period of time.

4. A signal processing circuit as defined in claim 1 which further comprises means for delaying the operation of said amplitude hold circuit for a predetermined period of time following recognition of said transient pulse by said pulse recognition means to cause substantially the peak amplitude of said pulse to be held by said amplitude hold circuit for subsequent sampliNg by said analog-to-digital converter.

5. A signal processing circuit as defined in claim 3 wherein said transient pulse recognition means include a filter circuit for passing only transient pulses, and an absolute-value detector circuit responsive to the transient pulses passed by said filter circuit for producing a control signal for application to said multivibrator, the polarity of said control signal being independent of the polarity of said transient pulses.

6. A signal processing circuit as defined in claim 1 wherein said analog input signal comprises an EKG signal and said transient pulses comprise pacemaker pulses superimposed thereon.

7. A signal processing circuit for use in conjunction with a data collection system wherein an anlog input signal is sampled at periodic spaced intervals and applied to an analog-to-digital converter to develop a digital output signal for causing said system to respond to a transient pulse appearing in said analog input signal between said periodic samplings, said signal processing circuit comprising, in combination:

means including a filter circuit for passing only transient pulses in said analog signal;

means including an absolute-value detector circuit responsive to the transient pulses passed by said filter circuit for producing a control signal;

the polarity of said control signal being independent of the polarity of said transient pulses;

means including a multivibrator responsive to said control signal for producing a control pulse of predetermined duration following the occurrence of said transient pulse; and

means including an amplitude hold circuit responsive to said control pulse for maintaining the instantaneous level of said analog input signal as applied to said analog-to-digital converter constant for the duration of said pulse, thereby causing said data collection system to sample said transient pulse.

8. A signal processing circuit as defined in claim 7 wherein said hold period corresponds substantially to the period between successive samplings of said analog input signal by said data collection system.

9. A signal processing circuit as defined in claim 7 which further comprises means for delaying the operation of said amplitude hold circuit for a predetermined period of time such that substantially the peak amplitude of said transient pulse is maintained by said amplitude hold circuit.

10. A signal processing circuit as defined in claim 7 wherein said analog input signal comprises an EKG signal and said transient pulses comprise pacemaker pulses superimposed thereon.

11. A signal processing unit comprising, in combination;

signal input means for receiving an input signal;

signal output means from which a processed output signal may be taken;

processing means coupled between said input and said output and including means for detecting the presence in a received signal of narrow pulses, and means, responsive to said detecting means detection of a narrow pulse, for holding and reproducing the narrow pulse, so as to deliver an expanded pulse to said output means but otherwise delivering substantially the input signal thereto.

12. A sampling-type EKG data collection and display system, comprising:

a plurality of sensors (10,

     11) for developing EKG electrical signals;

a signal processing unit (13,

     14) as defined in claim 11 for each of said plurality of sensors for coupling to receive an EKG signal therefrom at its said signal input;

means (16-18) for coupling periodically the output signals from said output of each of said processing units and for reproducing said EKG signals from said sampled signals, said sampling rate and duration of each sample being related to the expanded pulse width delivered by said processing units so as to insure reproduction of pulses detected thereby.

13. A data collection system for sampling an analog input signal at periodic intervals to develop a digital output signal, said system comprising, In combination:

an analog-to-digital converter for converting said analog input signal to said digital output signal;

pulse discrimination means for producing a control signal in response to the occurrence of said transient pulse; and

means including an amplitude hold circuit responsive to said control signal for maintaining the insntantaneous level of said analog input signal as applied to said analog-to-digital converter constant for a predetermined hold period following the occurrence of said transient pulse such that the amplitude of said pulse is sampled by said converter and converted to a corresponding digital output signal.

14. A data collection system as defined in claim 13 wherein said predetermined hold period is substantially equal to the sampling period of said data collection system.

15. A data collection system as defined in claim 13 which further comprises means for delaying the operation of said amplitude hold circuit for a predetermined period of time following recognition of said transient pulse by said pulse recognition means to cause substantially the peak amplitude of said pulse to be held by said amplitude hold circuit for subsequent sampling by said analog-to-digital converter.

16. A data collection system as defined in claim 13 wherein said analog input signal comprises an EKG signal and said transient pulses comprise pacemaker pulses superimposed thereon.

17. A data collection system for sampling an analog input signal at periodic intervals to develop a digital output signal, said system comprising in combination:

an analog-to-digital converter for converting said analog input signal to said digital output signal;

means including a filter circuit for passing only transient pulses in said analog signal;

means including an absolute-value detector circuit responsive to the transient pulses passed by said filter circuit for producing a control signal;

the polarity of said control signal being independent of the polarity of said transient pulses;

means including a multivibrator responsive to said control signal for producing a control pulse of predetermined duration following the occurrence of said transient pulse; and

means including an amplitude hold circuit responsive to said control pulse for maintaining the instantaneous level of said analog input signal as applied to said analog-to-digital converter constant for the duration of said pulse, thereby causing said data collection system to sample said transient pulse.

18. A data collection system as defined in claim 17 wherein the duration of said pulse substantially corresponds to the period between successive samplings of said analog input signal by said data collection system.

19. A data collection system as defined in claim 17 which further comprises means for delaying the operation of said amplitude hold circuit for a predetermined period of time such that substantially the peak amplitude of said transient pulse is maintained by said amplitude hold circuit.

20. A data collection system as defined in claim 17 wherein said analog input signal comprises an EKG signal and said transient pulses comprise pacemaker pulses superimposed thereon.