JPH0448167B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit configuration of a distortion detector using diode elements.

[Conventional technology]

Diffusion gauges are widely used as conventional semiconductor strain gauges. Furthermore, changes in resistivity due to the strain of the object to be measured due to the piezoresistance effect of this semiconductor strain gauge are converted into voltage output by a Whiston bridge circuit.

[Problem that the invention seeks to solve]

The value measured by this diffusion gauge is the average value of the strain value over the entire length of the gauge, making it impossible to measure strain in a minute area. Also, the output voltage of the Whiston bridge circuit is affected by fluctuations in the power supply voltage applied to this circuit. There were some drawbacks.

It is known that strain detection can be performed by utilizing the property that when mechanical force is applied to a diode element, its electrical characteristics change, but conventional circuits apply a constant voltage bias or constant current bias to the diode element. The circuit configuration was complicated. In addition, the characteristics of the constant voltage bias circuit or constant current bias circuit affect the measured value, so there is a drawback that high measurement accuracy cannot be obtained.

The present invention eliminates such drawbacks, and provides a distortion detector using a diode element that enables strain measurement in a minute area, and a distortion detection circuit using a diode element that outputs a measurement voltage that is not affected by power supply characteristics. The purpose is to

[Means for solving problems]

A first aspect of the present invention includes a first diode element disposed at a strain detection point, a terminal for supplying a constant bias current to the diode element, and a terminal that supplies a constant bias current to the diode element in accordance with a mechanical strain applied to the diode. In the distortion detection circuit, the detection means includes a terminal voltage of the diode element applied to one input, and a reference voltage applied to the other input. , a differential input type negative feedback amplifier to which current negative feedback is applied, and an output terminal to which an output voltage of the negative feedback amplifier is introduced.

Further, the reference voltage is preferably a voltage generated across the second diode element to which current is supplied from a terminal common to the terminal supplying the bias current.

The second diode element can be a strain detection diode element disposed at a position where mechanical strain is applied in a direction substantially opposite to the direction of mechanical strain applied to the first diode element.

The strain detection point can be a diaphragm.

Preferably, the bias current has a value within a range in which the voltage value at the output terminal is maintained at a substantially constant value despite fluctuations in the current value.

A second invention of the present invention includes a diode element arranged at a strain detection point, a terminal for supplying a constant bias current to the diode element, and a terminal for supplying a constant bias current to the diode element, and a terminal for supplying a constant bias current to the diode element, and a terminal for supplying a constant bias current to the diode element. In a distortion detection circuit comprising a detection means for detecting electrical characteristics of a diode element, the detection means comprises:
A differential input type negative feedback amplifier in which the terminal voltage of the diode element is connected to the input via a capacitor and current negative feedback is applied, and an output terminal to which the output voltage of the negative feedback amplifier is guided. It is characterized by

[Effect]

The negative feedback of the negative feedback amplifier is such that the change in the terminal voltage of the diode element caused by a constant bias current supplied to this diode element in response to the change in the electrical characteristics of the diode element caused by mechanical strain is eliminated. Current passes through the circuit. A voltage proportional to this current develops at the output terminal. The voltage at this output terminal has a value corresponding to the amount of change in the electrical characteristics of the diode element.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A circuit according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit connection diagram showing the configuration of the circuit of the first embodiment. FIG. 2 is a circuit connection diagram showing the configuration of the circuit of the second embodiment. FIG. 3 is a circuit connection diagram showing the configuration of a third embodiment circuit. FIG. 4 is an outline drawing showing a diaphragm in which a strain detection diode is formed. FIG. 5 is a graph showing the relationship between the bias current and output voltage of the embodiment circuit with respect to the tension applied to the strain detection diode. FIG. 6 is a graph showing the relationship between bias current and output voltage of the example circuit.

First, the configuration of the circuit of the first embodiment will be explained based on FIG.

This embodiment circuit has a bias current supply terminal 10
, an output terminal 15 , a first resistor 1 , a distortion detection diode element 2 , a differential input type amplifier 3 , a feedback resistor 4 , a second resistor 5 , and a second diode element 6 .

The bias current supply terminal 10 is connected to the anode of the strain detection diode element 2 via the first resistor 1, and the cathode of the strain detection diode element 2 is connected to a common potential. Further, one end of the second resistor 5 is connected to the terminal 10, the other end of the second resistor 5 is connected to the anode of the second diode element 6, and the cathode of this diode element 6 is connected to a common potential. Ru. First resistor 1 and strain detection diode element 2
The connection point between the second resistor 5 and the diode element 6 is connected to the negative input of the amplifier 3, and the connection point between the second resistor 5 and the diode element 6 is connected to the positive input of the amplifier 3. The output of the amplifier 3 is connected to the output terminal 15, and the output of the amplifier 3 is connected to the negative input of the amplifier 3 via the feedback resistor 4.

Next, the operation of this first embodiment device will be explained based on FIG.

Since the strain detection diode element 2 changes its voltage-current characteristics in accordance with the strain caused by the external force applied to it, the terminal voltage of this diode element 2 ( _hereinafter referred to as , is called bias voltage.)
V _B tends to change (see Figure 5). This is applied to the negative input of amplifier 3. The potential of the positive input of amplifier 3 is constant. On the other hand, changes in the bias voltage V _B are suppressed by the action of the negative feedback amplifier composed of the amplifier 3 and the feedback resistor 4. With this suppressing effect, a negative feedback current value I _B2 , that is, a voltage V _s corresponding to the voltage change of the distortion detection diode element is outputted to the output terminal 15 .

The voltage at the connection point between the second resistor 5 and the diode element 6 changes when the value of the bias current supplied via the bias current supply terminal 10 changes. This connection point voltage is applied to the positive input of the amplifier 3 as a reference voltage, so that the output voltage of the output terminal 15 is not affected by changes in the bias current value.

Next, the configuration and operation of the second embodiment circuit will be explained based on FIG. 2.

In this second embodiment circuit, the bias voltage V _B of the first embodiment circuit is connected to the amplifier 3 via the capacitor 7.
is inputting to the negative input of . Furthermore, since the value of the reciprocal of the product of the capacitance value of the capacitor 7 and the resistance value of the feedback resistor 4 is set to be very small compared to the value of the angular displacement speed of the strain generated in the strain detection diode element 2, A voltage corresponding to the amplitude of this distortion is output to the output terminal 15. There is no need to apply a reference voltage to the positive input of the amplifier 3, and the positive input may be connected to a common potential.

Next, the configuration and operation of the third embodiment circuit will be explained based on FIG.

In this third embodiment circuit, a strain detection diode element 9 is used in place of the diode element 6 of the first embodiment circuit. Each diode element is arranged at a position where the direction of change in strain occurring in the first strain detection diode element 2 and the direction of change in strain occurring in the second strain detection diode element 9 are substantially opposite directions.
Therefore, a voltage approximately twice the output voltage of the first embodiment circuit is outputted to the output terminal 15.

Next, the operation of the embodiment device when the bias current I _B1 is within a range where the voltage value V _s at the output terminal is kept almost constant even when the current value fluctuates will be explained based on FIG. explain.

The value on the horizontal axis of the graph shown in Figure 6 is the bias current.
The current value of I _B1 is shown, and the value on the vertical axis shows the voltage value of the output voltage V _s , curve 61 and curve 62.
shows the relationship between the bias current I _B1 and the output voltage _Vs , and shows the mechanical strain generated in the strain detection diode 2 when the relationship shown by curve 61 is maintained, and the relationship shown by curve 62. The magnitude is different from the mechanical strain that occurs in the strain detection diode 2 when the strain detection diode 2 is opened.

Now, if the value of bias current I _B12 increases or decreases by ΔI in the vicinity of bias current I B12 whose value is smaller than the value of bias current I _B10 corresponding to the point where curves 61 and ₆₂ are almost saturated, output voltage V _s and bias I Although the value of the ratio to _B1 , that is, the sensitivity changes, the sensitivity remains almost constant with respect to changes in bias current I _B1 in the vicinity of bias current I _B11 , which has a value larger than the value of bias current I _B10 .

[Application example]

An example of application of the present invention is shown in FIG. FIG. 4a is a front view, and b is a side view. Strain detection diode elements 21 and 2 are provided in the flexible portion of the diaphragm 20.
2 and 23 are formed. The annular portion A of the diaphragm 20 is fixed, and the shape of the flexible portion is distorted in response to the pressure P, changing the voltage-current characteristics of the strain detection diode elements 21, 22, and 23. Each of the distortion detection diode elements 21, 22 and 23 is a distortion detection diode element used in the first to third embodiment circuits described above.

〔Effect of the invention〕

As described above, the present invention has the effect that stable strain measurement can be performed with a circuit of a simple configuration because the measured value measured by the strain sensor is not affected by fluctuations in the power supply supplied to the detection circuit.

In addition, since a diode element suitable for strain measurement in a minute area can be used as a strain sensor, there are fewer restrictions on its placement, and by placing it at a position where the direction of strain change is almost the opposite direction, the output value for a unit strain amount can be approximately 2. There is an effect that can be easily realized by doubling the amount.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing the configuration of a circuit according to a first embodiment of the present invention. FIG. 2 is a circuit connection diagram showing the configuration of a second embodiment circuit of the present invention. FIG. 3 is a circuit connection diagram showing the configuration of a third embodiment circuit of the present invention. FIG. 4 is an outline diagram showing a diaphragm in which a strain detection diode is formed. FIG. 5 is a graph showing changes in the electrical characteristics of the example circuit with respect to the tension of the diode element.
FIG. 6 is a graph showing the relationship between bias current and output voltage of the example circuit. 1, 4, 5, 8...resistance, 2, 9, 21, 22,
23... Distortion detection diode element, 6... Diode element, 3... Amplifier, 10... Bias current supply terminal,
15...Output terminal, 20...Diaphragm.

Claims (1)

[Claims] 1. A first diode element disposed at a strain detection point, a terminal for supplying a constant bias current to this diode element, and a terminal for supplying a constant bias current to this diode element, which changes in accordance with mechanical strain applied to the diode. In the distortion detection circuit, the detection means is provided with a terminal voltage of the diode element to one input, a reference voltage to the other input, and a current negative. A distortion detection circuit using a diode element, comprising: a differential input type negative feedback amplifier to which feedback is applied; and an output terminal to which an output voltage of the negative feedback amplifier is guided. 2. The distortion detection circuit using a diode element according to claim 1, wherein the reference voltage is a voltage generated across the second diode element to which a current is supplied from a terminal common to the terminal supplying the bias current. 3. The second diode element is a strain detection diode element disposed at a position where mechanical strain is applied in a direction substantially opposite to the direction of mechanical strain applied to the first diode element. A distortion detection circuit using a diode element according to scope 2. 4. A distortion detection circuit using a diode element according to claim 1, wherein the distortion detection point is a diaphragm. 5. The distortion detection circuit using a diode element according to claim 1, wherein the bias current has a value within a range in which the voltage value at the output terminal is maintained at a substantially constant value despite fluctuations in the current value. 6 A diode element placed at a strain detection point, a terminal that supplies a constant bias current to this diode element, and detecting the electrical characteristics of this diode element that change according to the mechanical strain applied to the diode. A distortion detection circuit comprising: a differential input type negative feedback amplifier in which the terminal voltage of the diode element is connected to the input via a capacitor and current negative feedback is applied; 1. A distortion detection circuit using a diode element, comprising an output terminal to which an output voltage of a negative feedback amplifier is guided.