Surgery – Truss – Pad
Patent
1993-09-03
1995-06-27
Cohen, Lee S.
Surgery
Truss
Pad
128902, 128905, A61B 50428
Patent
active
054271100
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a circuit arrangement for the processing of physiological measurement signals, which are taken by means of electrodes on a patient, having input amplifiers which are individually associated with the electrodes and which are each connected at a first input connection with the electrodes associated with them and at a second input connection with a common reference potential connection. A device is disposed downstream of the input amplifiers on the output side, for the formation of difference signals from the output signals each of two selectable input amplifiers. A calibration pulse generator is connected with one of the electrodes and the reference potential connection and generates a calibration pulse between the two.
DESCRIPTION OF THE RELATED ART
In such a circuit arrangement known from German Patent 2,429,955, the calibration pulse-generator generates a calibration pulse of defined height and duration between the input connections of the individual input amplifiers. In a device disposed downstream of the input amplifiers on the output side, difference signals are formed from the output signals of two selectable input amplifiers, so that the calibration pulse does not appear in the pertinent difference signals, on account of the difference formation. However, if one of the input amplifiers is defective, a pulse-type output error signal results in formation of the difference signals. In the known circuit arrangement, it is possible to detect defects in the input amplifiers, but not defects, which may occur at the electrodes and in their supply lines to the input amplifiers.
SUMMARY OF THE INVENTION
It is an object of the present invention is to improve the known circuit arrangement so that a testing of the electrodes and their supply lines to the input amplifiers is also possible.
According to the invention, this object is inventively achieved with the circuit arrangement of the initially indicated type having an additional amplifier connected by its input to the reference potential connection, and the output connection of the additional amplifier connected to an additional electrode on the patient. Upon the emission of a calibration pulse by the calibration pulse generator, a pulse component defined by the gain of the additional amplifier is fed to the patient via the additional electrode, while the reference potential connection is acted upon by the residual pulse component. Since all electrodes disposed on the body of the patient electrically connect with one another via the body impedance, the pulse component fed to the patient appears at all these electrodes. In the course of the subsequent formation of difference signals from the output signals of two selected input amplifiers, the pertinent pulse component is suppressed and accordingly does not appear. If, however, a defect occurs in the input amplifier which has participated in the formation of the different signal or in the electrode supply line between the input amplifier and the associated electrode, or if the pertinent electrode has faulty contact with the body of the patient, then this defect is expressed in the form of an output pulse in the difference signal.
In an advantageous refinement of the circuit arrangement according to the invention, downstream of the outputs of the input amplifiers there is disposed a device for digital signal processing. In this device, prior to the actual signal processing of the output signals of the input amplifiers, the calibration pulse is subtracted and is added again to the signals after their digital processing. In this manner, the calibration pulse is excluded from the signal processing, so that, especially when using digital filters, these do not need to be designed to account for the calibration pulse. The frequency content of the calibration pulse differs considerably from that of the physiological measurement signals.
BRIEF DESCRIPTION OF THE DRAWINGS
The exemplary embodiments of the apparatus for a circuit arrangement for the processing of physiological measurement
REFERENCES:
patent: 4530365 (1989-07-01), Harada et al.
Danielsson Peter
Ohlsson Thomas
Cohen Lee S.
Jastrzab Jeffrey R.
Siemens Aktiengesellschaft
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