JPS644327Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a bioelectric potential measuring device such as an electrocardiograph or an electromyograph, and in particular to a means for controlling a muting circuit provided in a signal transmission path in response to the switching of a changeover switch that selects an input signal obtained via an electrode.

Generally, in biopotential measurement devices such as electrocardiographs, the input circuit is separated from the power supply and output circuit (isolation) to improve safety, withstand voltage, low leakage current, common mode rejection ratio (CMRR), etc. ), a so-called isolation amplifier is used.

FIG. 1 is a schematic block diagram showing an electrocardiograph consisting of an isolation amplifier using two transformers 1 and 2, and 3 to 5 are inputs for inputting input signals obtained via electrodes. Terminals 6 to 8 are buffer amplifiers, and 9 is a buffer amplifier 6 for selecting desired input signals, such as signals from the right hand and left foot or signals from two points around the heart.
10 is a differential amplifier, 11 is a modulator, 12 is a demodulator that demodulates the modulated signal transmitted through the transformer 2, 1
3 is a buffer amplifier, 14 is a filter circuit, 15
1 is a sensitivity switch, 16 is a main amplifier, and 17 is a galvanometer. The galvanometer 17 drives a recording pen in response to signals obtained at input terminals 3 to 5, thereby drawing an electrocardiogram.

Further, 18 is a DC power supply, 19 is a DC-DC consisting of an oscillator 20, a transformer 1, and a rectifier circuit 21.
This converter 19 connects each circuit, namely buffer amplifiers 6 to 8, differential amplifier 1.
0, the power supply voltage is supplied to the modulator 11.

In addition, an electrocardiograph requires a signal that is appropriately synthesized from signals obtained directly from the electrodes, such as the midpoint potential of both hands or the midpoint potential of both feet. The changeover switch 9 includes a resistor network 22, which is referred to as a resistor network 22.

By the way, when operating the changeover switch 9,
A large amount of noise is generated, which greatly disturbs the input signal obtained through the electrodes. This noise appears particularly when the input signal is small. Therefore, a muting circuit 23 is provided after the signal transmission path, for example, the filter circuit 14 in FIG.
This muting circuit must be controlled in accordance with the switching of the changeover switch 9.

Conventionally, as shown in FIG.
The rotary switch 25 switches the switch according to the rotation of the operating knob 24, and the rotary shaft 26 of the rotary switch 25 has a rotating shaft with concavities and convexities on the outer periphery having the same number and angle as the contacts of the rotary switch. By fixing the board 27 and moving the connecting rod 28 in accordance with the rotation of the rotary board 27, a separately provided muting contact 29 is opened and closed, and the opening and closing of the mutating contact 29 opens and closes the mutating circuit 23 provided in the signal transmission path. was under control. Note that the muting contact 29 is placed at a distance necessary for the withstand voltage required of the isolation amplifier.

However, in such a conventional switch, since the connecting rod 28 is connected to the rotary disk 27, the moderation (feeling) of the switch is hindered.
Switching operations become difficult. Furthermore, as for the timing of the muting, it is desirable that the muting be performed at the same time as the contact point of the switch starts to move, or just before that, but in the conventional system, the connecting rod 28 is moved in accordance with the rotation of the rotary disk 27, and thereby Since the mutating contact 29 is mechanically configured to open and close, it is difficult to obtain accurate timing for mutating, and therefore, it is also difficult to adjust it.

The present invention solves the above-mentioned drawbacks and ensures reliable muting, and will be described below with reference to FIGS. 3 and 4.

FIG. 3 is a side view showing the switch of the electrocardiograph according to the present invention and a photo sensor as a detection means for mutating, FIG. 4 is a partial perspective view of FIG. 3, and 30 is a switch operation knob. , 31 is a rotating shaft that rotates in accordance with the operating knob 30, 32 is a substrate, 33 is a pattern contact provided on the substrate 32 around the rotating shaft 31, and 34 is a movable contact 35 that comes into contact with the contact 33. , which is a rotating disk that rotates together with the rotating shaft 31. Then, as the operating knob 30 rotates, the movable contact 35 comes into contact with the contact 33 on the substrate 32, thereby switching the switch and selecting the input signal obtained via the electrode.

Further, on the outer periphery of the rotary disk 34, there is a number of switching points, that is, 3 contacts.
3 and the number of contact points of the movable contact 35,
A plurality of slits 36 are provided at the same angle as the switching angle, and the width of the slits 36 is selected to be narrower than the contact distance between the movable contact 35 and the contact 33. A rotary disk 34 including this slit 36
A photo sensor 39 consisting of an LED 37 as a light emitting element and a photo transistor 38 as a light receiving element is arranged on the substrate 32 so as to sandwich the outer periphery of the photo sensor 39. The provided mutating circuit 23 is controlled.

Therefore, before switching the switch, LED37
light is supplied to the phototransistor 38 through the slit 36, a detection signal is generated from the photo sensor 39, and muting is canceled. However, when the operating knob 30 is rotated to change the switch, the contact 33 and the movable contact Just before the slit 35 leaves, the slit 36 leaves the detection range of the photo sensor 39, and the rotary disk 34 causes the slit 36 to move out of the detection range of the photo sensor 39.
Since the light of 7 is blocked, the detection signal of the photo sensor 39 is no longer generated. That is, muting occurs immediately before the contact 33 and the movable contact 35 are separated. Then, when the movable contact 35 comes into contact with the next contact on the board 32 at the next switching position, the next slit provided on the rotary disk 34 comes within the detection range of the photo sensor 39, so mutating occurs again. It will be canceled.
In order to reliably release the muting after the switching is completed, this can be easily achieved by providing the muting circuit 23 with a time constant circuit such as C or R. Further, the photo sensor 39 needs to be placed at a distance necessary for the withstand voltage required of the isolation amplifier. Furthermore, the present invention can also be applied to biopotential measuring devices other than electrocardiographs, such as electromyographs.

As mentioned above, the biopotential measuring device according to the present invention uses a photo sensor to extract the signal that controls the mutating circuit, so the switching mode of the switch that selects the input signal obtained through the electrode is controlled. There is no damage, the adjustment is easy, and the number of parts can be reduced because there is no need for a muting contact like in the past. moreover,
By narrowing the width of the slits provided on the rotary disk, muting can be reliably applied just before switching the slits, making it possible to prevent the generation of noise due to switch switching, which is of high practical value.

[Brief explanation of the drawing]

Figure 1 is a schematic block diagram showing a general electrocardiograph constructed using an isolation amplifier.
3 is a side view of the main part of the electrocardiograph according to the present invention, and FIG. 4 is a partial perspective view of FIG. 3. Explanation of main drawing numbers, 1, 2...Transformer, 3-5
... Input terminal, 9 ... Selector switch, 19 ...
DC-DC converter, 23... Muting circuit, 29... Muting contact, 30... Operation knob, 31... Rotating shaft, 32... Board, 33...
Contact, 34... Rotating disk, 35... Movable contact, 36
...Slit, 39...Photo sensor.

Claims (1)

[Scope of utility model registration request] A biopotential measurement device in which an input signal obtained through an electrode is selected by a changeover switch, a muting circuit is provided in a transmission path for an output signal of the changeover switch, and the muting circuit is controlled in accordance with the changeover of the changeover switch, The changeover switch has a rotating shaft that rotates in response to a switching operation, a contact provided on a substrate around the rotating shaft, and a movable contact that rotates together with the rotating shaft and contacts the contact on the substrate. The slit has a width narrower than the contact distance of the contact point, and a photo sensor is provided to sandwich the outer periphery of the rotary disk. A biopotential measuring device characterized in that the mutating circuit is controlled by a detection signal.