JPH053861A - Electrocardiogram analyzing device - Google Patents

Abstract

PURPOSE:To allow the use of an inexpensive A/D converter of a low resolving power (>=10 bits) by biasing an analog input signal with a D/A converter in such a manner that the A/D conversion of the previous time is the center of the reference voltage in the A/D converter. CONSTITUTION:The electrocardiogram signal detected from an electrode mounted to a person to be detected is amplified by a differential main amplifier section 1. The electrocardiogram signal outputted therefrom is subjected to A/D conversion by the A/D conversion section 3. The difference between the conversion data obtd. therefrom and the center of the reference voltage 8 in the A/D converter 3 is calculated in a computing section 4. The output of a differential amplifier 2 is biased by the D/A converter 6 to the center of the reference voltage 8 according to the digital data obtd. therefrom. On the other hand, the output of the computer 4 is delivered as the result of the analysis and is stored into a memory section 5. Only the difference from the data of the previous time is inputted to the A/ D converter 3 and the reference voltage 8 thereof is dropped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrocardiogram analyzer,
In particular, it relates to an A / D converter.

[0002]

2. Description of the Related Art In a conventional electrocardiogram analyzer, an output of an amplifier for inputting and amplifying an electrocardiogram signal detected from electrodes is A.
A / D converter is directly input to the A / D converter, and the resolution of the A / D converter is determined according to the input dynamic range required for the device. A / D conversion for satisfying the specifications as an electrocardiogram analyzer The performance of the vessel is at least 1
Use an A / D converter with a resolution of 2 bits or more,
Performance of about 5 μV per 1 LSB (input conversion) was realized.

[0003]

Conventionally, an A / D converter of an electrocardiogram analyzer is designed so that a wide input dynamic range can be obtained even when a signal having a large baseline fluctuation is input as an input signal. Although the reference voltage of is set, in order to widen the input dynamic range, A /
On the contrary, if the reference voltage of the D converter is increased, the analog amount expressed per LSB is increased. Therefore, at least the resolution of 12 bits is required to satisfy the specifications (5 μV in input conversion) required by the current analyzer. The above A / D converter must be used, and low cost low resolution products (1
There is a problem in terms of price that A / D converters of 0 bits or less cannot be used.

[0004]

An electrocardiogram analyzing apparatus of the present invention is a differential amplifier for inputting and amplifying an electrocardiographic signal detected from electrodes attached to a subject, and an A / D for the differential electrocardiographic signal. An A / D converter for conversion, an arithmetic unit for calculating the difference between the conversion data obtained by the A / D converter and the center of the reference voltage of the A / D conversion, and the arithmetic unit The obtained digital data is output as an analysis result, and a D / A converter for biasing the output of the differential amplifier to the center of the reference voltage of the A / D converter by the output is provided.

[0005]

The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The output of the differential main amplifier 1 that amplifies the electrocardiogram signal detected from the electrodes attached to the subject moves positively and negatively around the ground potential, but the input voltage of the A / D converter 3 is changed by the bias circuit 2. It is input to the A / D converter 3 which is biased with respect to the ground potential so as to fall within the range. When determining the bias value, the switch 7 is set to the side b before the normal A / D conversion is started, and the reference voltage OV is A / D.
D / A converter 6 so that it becomes Vref / 2 of D converter 3
Adjust the output of.

Next, the switch 7 is turned to the a side to start the normal A / D conversion processing. At this time, the A / D conversion value and Vre
The difference data of f / 2 is calculated by the calculation unit 4, and the output of the D / A converter 6 is controlled by this data and is output as the analysis result. Therefore, the converted value of the previous data is A / D
D so that the reference voltage of the converter 3 is always in the center
The output of the / A converter 6 is controlled, and only the difference from the previous A / D converted value data is A / D converted by the A / D converter 3. Since the data converted by the A / D converter 3 is the difference data from the previous data, the calculation unit 4 and the memory 5
In this way, the previous data and the difference data are added to obtain the digital data for the actual analog input.

[0008]

As described above, the present invention is based on the previous A
By biasing the analog input signal by the D / A converter so that the / D conversion data becomes the center of the reference voltage of the A / D converter, only the difference from the previous data is input to the A / D converter. Therefore, it becomes easy to lower the reference voltage of the A / D converter and increase the amplification degree of the main amplifier section. Therefore, even if the resolution of the A / D converter is about 8 bits, the specification of 5 μV per 1 LSB of the A / D converter can be satisfied. In other words, when a 12-bit A / D converter is used in the normal A / D system, the maximum gain of the pre-stage amplifier section is about 250 times considering the baseline fluctuation. Since it is possible to raise the gain and lower the reference voltage, if the amplifier gain is set to 500 times and the reference voltage is set to 2.5V, 4.8 μV can be achieved per LSB even if an inexpensive 10-bit A / D converter is used. It has the effect of being able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

[Explanation of symbols]

 1 differential / main amplifier section 2 bias circuit 3 A / D converter 4 arithmetic section 5 memory section 6 D / A converter 7 switch 8 reference voltage (Vref) 9 bias voltage

Claims (1)

Claim: What is claimed is: 1. A differential amplifier for inputting and amplifying an electrocardiogram signal detected from electrodes attached to a subject, and an electrocardiogram signal output from the differential amplifier. And an arithmetic unit for calculating the difference between the conversion data obtained by the A / D converter and the center of the reference voltage for A / D conversion. An electrocardiogram comprising: a D / A converter that outputs digital data as an analysis result and biases the output of the differential amplifier to the center of the reference voltage of the A / D converter by the output. Analyzer.