JPH07260525A - Sensor - Google Patents

Abstract

PURPOSE:To provide a sensor in which electric wire for wiring is reduced so as to facilitate wiring and to prevent miswiring. CONSTITUTION:A sensor 1 has a detecting element 2 and a signal processing circuit 3. The sensor 1 is connected to a control circuit 8 by a connecting wire 5 serving also as a power feeder line and a signal output line. When the output from the detecting element 2 is less than the specified value, the output terminal 4D of a comparator 4 is on a high level or in a high impedance state, so that a capacitor 7 is in the charged state, and the input to the amplifier 9 of the signal judging circuit of a control device 8 is on a high level. When the output from the detecting element 2 becomes the specified value or more, the output terminal 4D of the comparator 4 is on a low level, so that the input to the amplifier 9 is also on a low level, and the action of the detecting element is positively transmitted. At this time, the sudden electric discharge of the capacitor 7 is prevented by a diode 6, and the comparator 4 is continuously driven by electric charge accumulated in the capacitor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for outputting a signal to a control device or the like, which has a detection element for converting a physical chemical quantity such as magnetism, heat, light, stress, chemical change and radiation into an electric signal. In particular, the present invention relates to a sensor in which the main body of the sensor is separated from the control device and which is connected by an electric wire or the like.

[0002]

2. Description of the Related Art In a conventional sensor, when an output signal or sensitivity of a detection element is low, a noise signal entering from an electric wire on the way becomes larger than an output signal of the sensor or receives a signal of a processing device. If the threshold level is exceeded, malfunction may occur or accurate measurement work may not be possible. Therefore, an electronic circuit compensates the signal from the detection element and amplifies it to an easy-to-use output.
Noise resistance may be improved by performing signal processing.

In the case of performing such processing, as shown in FIG. 6, for each sensor 103 having a detection element 101 and a signal processing circuit 102, a sensor 103 is provided with a power supply line 104 to the signal processing circuit and a control device 105. The three electric wires of the signal output line 106 and the ground line 107 are required for connection with the control device 105, and if a connector is used for the connection in the middle, naturally three terminals are also required.

[0004]

Generally, when the sensor and the control unit are arranged apart from each other, the cost increases as the length and the number of electric wires used for connection between them increase, and the number of parts increases. As a result, the mounting process becomes complicated, and the failure rate and failure rate due to wiring mistakes increase. Therefore, for example, when the sensor of FIG. 6 is used in an automobile or the like, one of the electric wires can be omitted by diverting the ground wire from the body, but two electric wires are still required. Therefore, it is required to reduce the cost by reducing the number of electric wires, simplify the mounting process, and further reduce the weight of the entire device.

[0005]

Therefore, in the sensor of the present invention, a detection element for converting a physical chemical quantity such as magnetism, heat, light, stress, chemical change and radiation into an electric signal and outputting the electric signal, and processing the electric signal. A signal processing circuit comprising a signal processing circuit, a power source terminal of the signal processing circuit is connected to a power source through a resistor and a diode, and at the same time, an output terminal of the signal processing circuit is connected to an intermediate point between the resistor and the diode. A capacitor for holding the power supply voltage of the signal processing circuit when the power supply from the power supply is cut off is connected to the power supply terminal, and the capacitor of the signal processing circuit is maintained while the detection element does not output a predetermined condition. The output is in a high level or high impedance state, the potential of the power supply terminal of the signal processing circuit is substantially the same as the power supply, and the capacitor is in a charged state. The input to the signal judgment circuit of the control device is maintained at a high level, and when the detection element performs an output satisfying a predetermined condition, the output of the signal processing circuit becomes a low level and the power supply to the signal processing circuit is temporarily cut off. The signal processing circuit is continuously driven by the electric charge accumulated in the capacitor, and the input to the signal determination circuit of the control device also becomes low level, and the power supply from the power source to the signal processing circuit and the signal determination circuit The signal is output from the signal processing circuit to the same electric circuit.

Further, in the sensor of the present invention, when the detection element outputs an output satisfying a predetermined condition, the output of the signal processing circuit becomes a repeated output of low level and high level, and the input to the signal determination circuit of the control device is also low. When the output of the signal processing circuit goes low and the output of the signal processing circuit becomes low level, the power supply to the signal processing circuit is temporarily cut off, but the signal processing circuit continues due to the charge accumulated in the capacitor. It is characterized in that the power supply from the power source to the signal processing circuit and the signal output from the signal processing circuit to the signal determination circuit are performed by the same electric circuit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an example in which the present invention is used in a magnetic rotation sensor 1, and FIG. 2 shows an output waveform of this sensor 1. The rotation sensor 1 is composed of a detection element 2 and a signal processing circuit 3.

As shown in FIG. 7, for example, the detection element 2 has a structure in which a coil 2B is wound around an iron core 2A, and a magnetic material attached to a rotating body to be measured is brought close to or open to the detection surface 2C. The change in magnetic flux around the detecting element 2 due to separation is detected by the coil 2B.
It is detected as a voltage change at both ends. The detection element is not limited in its form as long as it can convert a physical displacement into an electric signal, but it is more preferable to use one having a small power consumption such as the above-mentioned example, a piezoelectric element, or a phototransistor.

The signal processing circuit 3 is mainly composed of a comparator 4 for processing a signal from the detection element 2. One terminal of the detection element 2 is connected to an inverting input terminal 4A of the comparator 4. The non-inverting input terminal 4B is connected to the power supply terminal 4C via the resistor R1 and is also grounded via the resistor R2. The output terminal 4D of the comparator 4 is connected to the connection electric wire 5 and also connected to the power supply terminal 4C via the diode 6. In addition, power supply terminal 4
C is grounded via the capacitor 7. 4E
Is a ground terminal.

The other end of the connecting electric wire 5 is connected to the input / output terminal 8A of the control device 8. The input / output terminal 8A is connected to the input terminal of the amplifier 9 of the signal determination circuit, and the power supply voltage V is applied via the resistor R3. Figure 1
In FIG. 1, the parts other than the amplifier 9 of the signal judging circuit are omitted, but it goes without saying that other parts such as a judging device and an output circuit are included.

Next, the operation of the sensor 1 will be described. When there is no output from the detection element 2 such as when the measuring object is not rotating, or when the output from the detection element 2 is below the threshold level of the comparator 4 which is determined by the power supply voltage V and the resistors R1, R2 and R3. In case of voltage,
The output from the output terminal 4D of the comparator 4 becomes high level or high impedance state. At this time, power is supplied to the power supply circuit of the comparator as indicated by arrow A, and the capacitor 7 is charged via the resistor R3 on the control device side and the diode 6 on the sensor side.

When the output voltage from the detection element 2 input to the inverting input terminal of the comparator 4 exceeds the threshold level, the comparator 4 becomes low level and the potential of the output terminal 4D decreases, so that the current flows through the path of arrow B. The power supply to the flow power supply terminal 4C is temporarily cut off, but the electric charge stored in the capacitor 7 causes the comparator 4 to continue operating. At this time, the diode 6 prevents sudden discharge of the capacitor 7. Further, since the input level to the control device 8 is also lowered, the operation of the detection element 2 is surely transmitted to the control device 8. Further, the capacitor 7 is gradually discharged by driving the comparator 4, but when the output from the detection element 2 disappears, the output of the comparator 4 becomes high level or high impedance state and the capacitor 7 is charged.

As described above, according to the present invention, since the power supply wire and the signal output wire can be made common, one wire can be reduced as compared with the conventional one, and the electric wire can be used in the automobile. When a structure such as a body is used as a grounding wire like the electrical equipment used, only one electric wire can be used.

The output of the sensor at this time will be described. The output voltage of the detection element 2 and the voltage of the output terminal 4D of the comparator 4 have the relationship shown in FIG. When a control signal is input to the control device 8, the threshold level of the input voltage is defined in order to avoid the influence of noise, which is usually unavoidable. For example, when the output from the detection element 2 is directly input to the control device, Vx is defined as the lowest voltage, and the control device does not judge that the output of the detection element is valid at a voltage that does not exceed this level.
The higher this minimum voltage Vx, the higher the noise resistance, but
In principle, some devices have low output voltage, so it cannot be specified too high. Further, here, the electric wire for connection is inserted between the detection element 2 and the control device 8, and the longer the distance, the easier the noise is picked up.

Therefore, as in the above-mentioned example, the signal from the detection element 2 is processed by the comparator 4 and sent to the control device, so that if the output voltage from the detection element 2 changes beyond the threshold level of the comparator, that voltage changes. The comparator output reliably generates a constant potential difference regardless of the level of. Therefore, the threshold level Vy on the control device 8 side can be set to be larger than Vx as shown in FIG. 2, so that the noise resistance is improved.

As the signal processing circuit of this sensor, in addition to the comparator, for example, an operational amplifier, a bipolar transistor, an FET, or a logic IC having an appropriate input / output condition and threshold level can be used. A function similar to that of the shown comparator can be obtained and the object of the basic invention can be achieved.

In the above-described embodiment, the case where the operation time of the detection element is short and the non-operation time which is the charging period of the capacitor is long has been described as an example. However, for example, even when the operation time of the detection element is long and the non-operation time is short. It goes without saying that if the output of the detection element is input to the non-inverting input terminal 4B of the comparator 4 and the midpoint of the resistors R1 and R2 is input to the inverting input terminal 4A, the same operation as the above example can be performed. Absent. Further, when the threshold level of the comparator requires sufficient stability, a voltage stabilizing circuit may be provided instead of the resistors R1 and R2.

In the above example, the case where the signal output time from the detecting element per cycle is a repetitive waveform having a relatively short wavelength, such as rotation detection, has been described. If a very slow change is detected, the detection element output waveform will become long, and the method described above will take a long time for the comparator output to go low, and the capacitor will be discharged below the voltage required to maintain this sensor operation. The power supply to the comparator may not be in time. In such a case, power can be supplied from the control circuit side by providing the oscillator 10 in the signal processing circuit as shown in FIG. 3, for example.

This example will be described with reference to FIGS. 3 and 4. FIG. 3 is a circuit diagram of this embodiment, and FIG. 4 is a waveform diagram thereof. The same parts as those in the above-mentioned example are designated by the same reference numerals, and detailed description thereof will be omitted. In this sensor 11, the oscillator 10 is interposed between the output terminal of the comparator 4 of the signal processing circuit 13 and the connection wire 5. Although not shown, the control device is connected to the other end of the connection wire 5 as shown in FIG. 1 to supply power to the sensor side and input a signal from the sensor side.

The operation of the sensor 11 will be described. If there is no output from the detection element 2 or if the output is below the threshold level of the comparator 4, the output from the comparator 4 becomes high level or high impedance state, When this output is input to the control terminal 10A of the oscillator 10, the oscillator does not operate, the voltage on the output terminal 10B side remains high, and the capacitor 7 is supplied with power via the diode 6 as shown by the arrow C and charged. It The output from the detection element 2 is the comparator 4
When the threshold level is exceeded, the output from the comparator 4, that is, the input level to the control terminal 10A of the oscillator 10 becomes low level, and the oscillator 10 operates. During time T when the comparator output is at low level,
By the operation of the oscillator 10, the output of the output terminal 10B alternately repeats the low level state of t ₁ and the high level state of t ₂ at the cycle of t ₀ as shown in FIG. 4, so that the input level to the control device 8 also alternates. Change. Therefore, while the input to the control device 8 is changing, it can be determined that the detection element 2 is in the operating state. For example, the control device 8 integrates this signal to obtain information such as speed, rotation speed, time, and weight. Can be obtained from the sensor.

Here, t ₁ when the oscillator output is at the low level
During this period, the power supply flows as shown by arrow D in FIG. 3, so that it can be seen that the input of the determination device of the control device connected to the other end of the connection electric wire 5 also becomes low level and the detection element operates. During this time, the power supply terminal 4C of the comparator 4 and the power supply terminal 10 of the oscillator 10
The power supply to C is cut off, but the electric charge stored in the capacitor 7 causes the comparator 4 and the oscillator 10 to continue operating. Next, during the time t ₂ when the output of the oscillator becomes high level, power is supplied as shown by the arrow C and the capacitor 7 is charged. Even if the output of the detection element continues for a long time due to this repetition, the capacitor 7 will not be discharged below the voltage necessary to maintain the operation of the sensor, and the operation of the comparator can be reliably continued.

Further, in this case, if the output signal from the detection element 2 is a signal of a sufficient magnitude with respect to the control terminal 10A of the oscillator 10, the signal processing circuit is constructed around the oscillator 10 as shown in FIG. May be omitted. In FIG. 5 as well, the same parts as those in the above-mentioned example are designated by the same reference numerals and the description thereof will be omitted. In this case, the signal processing circuit 23 is configured centering on the oscillator 10, and the capacitor 7 has an arrow until the output signal input from the detection element 2 to the control terminal 10A of the oscillator 10 exceeds the threshold level for driving the oscillator 10. It is charged as indicated by C. When the output signal from the detection element 2 exceeds the threshold level, the oscillator 10 is driven, and during that time, the output of the output terminal 10B is alternately controlled by alternately operating the low level state and the high level state by the operation of the oscillator 10. The input level to the amplifier 9 of the signal determination circuit of the device 8 also changes alternately. Therefore, it can be determined that the detection element 2 is in the operating state while the input to the signal determination circuit is changing.

[0023]

According to the present invention, the electric wire for power supply and the electric wire for signal output between the sensor and the control device can be made common, so that one electric wire is reduced as compared with the conventional one. In addition, when a structure such as a body is used as a grounding wire such as an electric component used in an automobile, it is possible to use only one electric wire. Therefore, even when the sensor and the control unit are arranged apart from each other, the cost is reduced, the weight of the entire device is reduced, the process of connecting electric wires, the process of attaching wiring, etc. is facilitated, and the failure rate is reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment using a sensor of the present invention.

2 is an output waveform diagram of the sensor of FIG.

FIG. 3 is a circuit diagram showing another embodiment using the sensor of the present invention.

FIG. 4 is an output waveform diagram of the sensor of FIG.

FIG. 5 is a circuit diagram showing another embodiment using the sensor of the present invention.

FIG. 6 is a circuit diagram showing an example using a conventional sensor.

FIG. 7 is an example of a detection element used in the sensor of the present invention.

[Explanation of Codes] 1: Sensor 2: Detection element 3: Signal processing circuit 4: Comparator 5: Connection wire 6: Diode 7: Capacitor 8: Control device 9: Amplifier (signal determination circuit) 10: Oscillator

Claims (2)

[Claims] 1. A sensor comprising a detection element for converting physical and chemical quantities such as magnetism, heat, light, stress, chemical change, and radiation into an electric signal and outputting the electric signal, and a signal processing circuit for processing the electric signal. The power supply terminal of the signal processing circuit is connected to the power supply via the resistor and the diode, and at the same time, the output terminal of the signal processing circuit is connected to the intermediate point between the resistor and the diode, and the power supply terminal is supplied with power from the power supply. A capacitor for holding the power supply voltage of the signal processing circuit when it is cut off is connected, and the output of the signal processing circuit is in a high level or high impedance state while the detection element does not output a predetermined condition. The potential of the power supply terminal of the signal processing circuit is almost the same as that of the power supply, and the capacitor is in a charged state, while the input to the signal determination circuit of the control device is kept at high level. When the detection element outputs a signal satisfying a predetermined condition, the output of the signal processing circuit becomes low level and the power supply to the signal processing circuit is temporarily cut off, but the signal processing circuit is It is driven continuously, and the input to the signal judgment circuit of the control device also becomes low level, so that the power supply from the power supply to the signal processing circuit and the signal output from the signal processing circuit to the signal judgment circuit can be performed by the same electric circuit. A sensor characterized by what it does. 2. A sensor comprising a detection element for converting physical and chemical quantities such as magnetism, heat, light, stress, chemical change and radiation into an electric signal and outputting the electric signal, and a signal processing circuit for processing the electric signal. The power supply terminal of the signal processing circuit is connected to the power supply via the resistor and the diode, and at the same time, the output terminal of the signal processing circuit is connected to the intermediate point between the resistor and the diode, and the power supply terminal is supplied with power from the power supply. A capacitor for holding the power supply voltage of the signal processing circuit when it is cut off is connected, and the output of the signal processing circuit is in a high level or high impedance state while the detection element does not output a predetermined condition. The potential of the power supply terminal of the signal processing circuit is almost the same as that of the power supply, and the capacitor is in a charged state. When the detection element outputs a signal satisfying a predetermined condition, the output of the signal processing circuit is repeatedly output at low level and high level, and the input to the signal determination circuit of the control device is also repeatedly output at low level and high level. Then, the output of the signal processing circuit becomes low level, so that the power supply to the signal processing circuit is temporarily cut off, but the signal processing circuit is continuously driven by the charge accumulated in the capacitor, and A sensor characterized in that the power supply to the signal processing circuit and the signal output from the signal processing circuit to the signal determination circuit are performed in the same electric circuit.