JPS583408A - Variable gain pulse amplifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable gain pulse amplifier particularly suitable for phonocardiography. In phonocardiography, recordings of pulse curves, such as apical curves, carotid curves, and jugular curves, are often performed while the patient is holding his or her breath. For this purpose, recording should be done quickly, especially so that sick people can be examined without difficulty. In this case, the amplitude of the pulse curve is greatly influenced not only by the individual being examined but also by the installation of the signal detection device (for example a pulse microphone). For example, the jugular pulse often has a significantly smaller amplitude than the apical pulse.

The signal detection device is generally coupled to an S pulse amplifier, the gain of which must be adjustable within wide limits to compensate for large amplitude changes. Conventionally, gain changes are made using manually operated switches. ) When recording a pulse curve, the operator uses a pulse microphone, e.g.
Manual manipulation is typically used to find the most favorable storage location. If you try to record two pulse curves at the same time, your hands will be full. Therefore, a separate operator is required to adjust the correct gain.

Furthermore, manual adjustment is laborious and, as already mentioned,
This poses a particularly heavy burden on patients. .

It is an object of the present invention to enable the gain in a pulse amplifier to be quickly and accurately matched to the pulse curve to be measured.Another object of the present invention is to enable the gain to be quickly and accurately matched to the pulse curve to be measured. The goal is to make it possible.

The first purpose is to provide a divider as an amplifier, and input a signal to be amplified into the numerator input to the input side of the divider, and input a signal corresponding to an amplitude range covered within a predetermined time. This is accomplished by deriving it as a denominator input. ,
By effectively dividing the pulse signal by its own amplitude in this way, a pulse curve with an approximately constant amplitude range results at the output of the divider.

To determine the denominator, an embodiment of the invention provides a known amplitude scanner that tracks the peaks of the signal amplitude over a predetermined time interval. Depending on the selection of the constant scanning time, different lower frequency limits for the pulse curve to be measured result. For example, for a phonocardiograph, the scan time is 1.
If set to 6 seconds, that means the minimum pulse frequency is about 38 pulses per minute. After the end of the scan time, the output signal of the amplitude scanner is almost a divisor. This can be led to the denominator input of the divider, for example via a sample and hold circuit.

Until the end of a new scanning process, this sample and hold value serves as the denominator input of the divider and thus defines the gain. When recording pulse curves, this automatic gain adjustment can be used to increase pulse amplitude if the pulse shape is important, for example to the examining physician.

It is already sufficient to be able to display major differences on a convenient scale.

Further, in embodiments of the present invention, the output signal of the amplitude scanner is regularly compared with a stored value, and the stored value is replaced with the output signal of the amplitude scanner when the resulting deviation exceeds a predetermined value. By providing a comparator for this purpose, we aim to further improve curve display. The output signal of the amplitude scanner can vary within certain limits without resulting in a gain change. Thereby, the pulse curve can be displayed over a longer period with a unified gain even if there is a certain difference in amplitude.

In order to display the magnitude of the pulse curve at the same time, one particularly advantageous embodiment of the invention provides a verification signal generator which is turned on for a short time during the exchange of the stored value and determines the amplitude of its signal by the stored value. A is fine. As a result, it is possible to perform the verification so that a predetermined voltage corresponding to a predetermined measurement signal is applied to the input terminal of the pulse amplifier with the standard sensitivity of the signal detection device. The amplitude of the resulting pulse curve and the calibration signal can be compared and the amplitude of the pulse lead can then be calculated. A particularly simple evaluation of the measurement curve is obtained if the verification signal generator is turned on once before and once after replacement.

The pulse amplifier according to the invention automatically adjusts the gain so that the recorded pulse curve obtains a preselected amplitude. The adjustment time then depends on the selected time interval for the amplitude scanner. Each recording section with a predetermined amplitude is separated by two test pulses. The test pulse preferably has a waveform cut out of a triangle having side edges with a slope corresponding to the gain. This also verifies the derivative of the measured pulse curve. The actual test pulse is made into a rectangular pulse with an amplitude determined by the slope.

In order to further widen the possible measurement range, according to the invention each test pulse can also be associated with a special code which fixes the signal amplitude to be processed over a wide range.

Repeated scanning in a simple and reliable manner.

In order to synchronize the comparison and the possible exchange in time, a pulse generator is provided which controls the corresponding amplifier components.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a pulse amplifier according to the present invention, and FIG. 2 is a waveform diagram showing an example of a pulse curve (taken out by the pulse amplifier).

The core of the pulse amplifier according to the invention is the divider l. The pulse signal to be measured comes via a line 2 from a pulse detection device, not shown. The magnitude of the pulse curve can be measured in various ways. One method is to measure the resulting volume change in a closed microphone placed over the point of impact. Other measurement methods use force measuring instruments that measure the force produced by the pulse to be measured when the movement of the major surface is prevented. For example, if a pulsed microphone is used, the sensitivity of the pulsed microphone can be tested by a pressure transmitter such that a given volume change produces a given output signal.

The signal coming from the pulse microphone is led via switch 3 to numerator input 11 of divider 1 . At the same time, this signal is guided to the amplitude scanner '4 via the conductor fR41.

The output signal of the amplitude scanner 4 reaches the analog memory 6 via the conductor #42 and the switch 5. Other guide IJ4
3, its output signal reaches a comparator 7. The stored value in each case reaches the denominator input terminal 12 of the divider l via a conductor 61, reaches the other input terminal of the comparator 7 via a cut conductor 62, and then passes through a conductor 63 to the verification signal. One input of the generator 8 is reached. 4 wire 71°72
Alternatively, via 73 the comparator controls the switches 3, 5 and the verification signal generator 8. The magnitude of the test signal is determined by the stored value. The output of the test signal generator 8 is led via a conductor 81 to the other terminal of the switch 3 and is connected to the numerator input 11 of the divider 17) from which the signal arrives via the conductor 2 from the microsensor. can be done. Via lines 94.degree. 97 and 98, the scanning, comparison and possible replacement as well as the time course of the verification are controlled by a control pulse generator 9.

The operation of this pulse amplifier is as follows.

A pulse signal is introduced to the numerator input of divider l.

At the same time, this signal is guided to an amplitude scanner 4. This tracks the amplitude of the signal for, say, 1.6 seconds. This 1.6 second time interval means that the lowest pulse frequency is on the order of 38 magnitude per minute. At the end of this time interval (search time) the scanned amplitude is compared in a comparator 7 with the voltage in the memory 6. When the deviation is small, i.e. when the deviation is below a predetermined limit, the memory 6
The voltage at does not change. When the deviation is greater than this predetermined limit, the voltage in memory is exchanged with the tracked amplitude.

This course is continuously and repeatedly controlled by control pulses 9. The voltage of the memory 6 is led to the divider 10 denominator input 12. The verification signal generator 8 is likewise controlled via the comparator 7. When a voltage comparison indicates an exchange of voltages in memory.

First, the verification signal generator 8 is turned on, and at the same time a verification pulse whose magnitude is determined by the old memorized value is sent to the divider 1.
The switch 3 is operated so that the molecule input end of the molecule is reached.

Immediately after that, switch 5 is operated and the contents of memory 6 are exchanged. Thereafter, the verification signal generator 8 is controlled once again, so that another pulse with a magnitude corresponding to the new stored value reaches the numerator input 11 of the divider. Therefore, the gain feminization in the recorded pulse curve is determined by the composite test pulse in each case. The composite test pulse consists of at least two test pulses, one indicating the old gain and one indicating the new gain, and preferably still has a code thereon each indicating the selected gain range. Consisting of

The output end of the splitter l is conductor IIj! 13, it is connected, for example, to a recorder for recording the pulse curve to be measured. The recorder is not shown in the block diagram of FIG.

FIG. 2 shows the time course of the carotid artery pulse curve. The upper part of the diagram shows the pulse course, and the lower part shows the first derivative of this pulse curve. At approximately the center of the time axis, the memory is replaced and the gain is changed due to the accompanying change in the denominator input of the divider 1. In the rectangular box is shown the composite test pulse required for the exchange, which consists of the 1V code consisting of narrow rectangular pulses of two different heights and the actual test pulse. Together, the code and pulse indicate the gain range and the gain determined by the margin. The partial pressure in the right rectangle is shown with a similar code and now with a test pulse having a different magnitude. During the pre-switch scan, the result of the next comparison is
A change in GAY/ is required to indicate that the amplitude has fallen below a predetermined limit. Therefore, a large gain is set on the right side of the pulse curve. To further examine the test pulse, the rise time of the pulse to plateau is always the same, so the slope is a direct measure of the magnitude of the gain. As shown at the bottom of FIG. 2, forming the first derivative of the pulse curve results in a differential verification pulse that again serves to verify the differential pulse curve.

The selection of the code allows the amplifier to be optimally adapted to the large amplitude changes that occur when accepting different measurement curves.
In order to record with as good a resolution as possible,
A selection can be made between various gain ranges.

Therefore, by automatically adjusting the gain, the burden on the patient can be reduced to a minimum during the examination using heart sound recording.
The gain can be quickly and reliably adapted to the measurement conditions. Along with this, errors due to the intervention of multiple operators that would otherwise be required can be avoided. However, the pulse amplifier according to the invention is not limited to the measurement of pulse curves using a phonocardiograph (it can be applied to a wide range of measurement techniques for detecting various pulse curves with strongly fluctuating amplitudes).
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[Brief explanation of the drawing]

FIG. 11 is a block diagram schematically showing a pulse amplifier 111g according to the present invention, and FIG. 2 is a waveform diagram illustrating a pulse curve obtained by this pulse amplifier. ■...Divider, 11...Numerator input terminal, 12...Denominator input terminal, 3, 5...Switch, 4...Width scanner,
6...Memory, 7...Comparator, 8...Verification signal generator. 9...l'' control pulse generator.

Claims (1)

[Claims] 1) A signal to be amplified is introduced as a molecular input. 1. A variable gain pulse amplifier characterized in that a divider is provided in parallel with the amplifier to which a signal corresponding to an amplitude range covered by a predetermined time is guided as a denominator input. 2) A pulse amplifier according to claim 1, further comprising an amplitude scanner for tracking the signal amplitude over a predetermined time interval to determine the amplitude range. 3) The output signal of the amplitude scanner can be led to a memory,
3. A pulse amplifier according to claim 1, wherein the current value of this memory provides a signal for a denominator input of said divider. 4) A comparator is provided that regularly compares the output signal of the amplitude scanner with the value stored in the memory and, when there is a deviation of more than a predetermined value, replaces the value stored in the memory with the output signal of the amplitude scanner. A pulse amplifier according to any one of claims 1 to 3. 5) A verification signal generator is provided, which is turned on for a short time when exchanging stored values, and whose signal amount is determined by the stored value in the memory. 4. The pulse amplifier according to any one of Item 4. 6) The pulse amplifier according to claim 5, wherein the verification signal generator is turned on once before and after replacement. 7) The verification pulse has a triangular waveform. 7. The pulse amplifier according to claim 5, wherein the side edges thereof have a slope corresponding to the gain. 8) The pulse amplifier according to any one of claims 5 to 7, characterized in that each test pulse is associated with a code. 9) Pulse amplifier according to any one of claims 1 to 8, characterized in that a control pulse generator is provided for controlling the continuous repetition of tracking, comparison and exchange. 10) A pulse amplifier according to any one of claims 1 to 9, characterized in that the signal to be amplified is extracted by a certified signal detection device. 11) a divider having a numerator input and a denominator input; a signal detection device for the pulse to be amplified, the output of which is connected to the numerator input of the divider; an amplitude scanner connected to the output terminal for tracking the signal width over a predetermined time interval; an amplitude scanner having an output signal guided therethrough and having an output connected to the denominator input of the divider; a memory; a comparator for comparing the output signal of the amplitude scanner and the output signal of the memory and passing the output value of the amplitude scanner as a new stored value when there is a deviation of a predetermined value or more; and the comparator; and a control pulse generator for repeatedly controlling the amplitude scanner, the comparator, and the verification signal generator. The pulse amplifier according to any one of items 5 to 9.