JPH07280848A - Optical sensor - Google Patents

Abstract

PURPOSE:To sustain high accuracy by a constitution wherein energy is fed from a voltage or current to be measured and an optical signal of corresponding frequency is generated and converted into an electric signal in order to eliminate the eliminate the influence of optical transmission loss and the variation of characteristics at a light receiving section. CONSTITUTION:A capacitor C is charged with an input voltage Vi through a resistor R and when the charged voltage reaches a highest,level Vp, an optical control switch circuit PSW receives an optical signal OPT. and conducted. When the capacitor C is discharged and the voltage thereof drops down to a lowest level Vb, the signal OPT. attenuates abruptly to interrupt the circuit PSW. The capacitor C is charged again thus repeating the charging and discharging operations. Since the charge/discharge frequency is dependent on the input voltage Vi, time input voltage Vi can be detected from the output voltage Vo when the charge/discharge frequency is converted into the output voltage Vo through a frequency/voltage converter F/V. Furthermore, accuracy in the the measurement is not susceptible to the transmission loss because the voltage Vi is transmitted optically while being converted into a frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor used for voltage or current monitoring.

[0002]

2. Description of the Related Art Conventionally, as this type of device, for example,
Optronics Co., Ltd. published "Optical Sensor Technology Collection" (Published February 19, 1990), "Voltage Sensors, Magnetic Field Sensors" on pages 31-32. The intensity of an electric field or a magnetic field is measured by changing the polarization state of the light passing through the current sensor into a change in the intensity of the light through an analyzer.

This has a structure as shown in FIG. In FIG. 7, OS is a light source such as a semiconductor light emitting element,
OF is an optical fiber, S is an optical sensor element, O / E is a photoelectric conversion unit, and So is a sensor output. As the optical sensor element S, a Pockels element having an electro-optical effect is used when measuring a voltage, and a Faraday element having a magneto-optical effect is used when measuring a current.

[0004]

The conventional device having the above-mentioned structure has the following problems. (1) Two optical fibers are required. (2) The measurement accuracy is affected by the transmission loss fluctuation of the optical fiber, the gain fluctuation of the light receiving part, and the linearity. (3) The sensor element is expensive.

In order to solve such problems, the present invention has an object to provide an optical sensor having the following features. (1) The measurement accuracy is not affected by the transmission loss of the optical transmission system, the linearity of the light receiving system, and the gain fluctuation. (2) No power supply is required for the sensor section. (3) The transmission system is insulated. (4) It can be composed of one optical fiber. (5) It can be composed of an inexpensive element.

[0006]

In order to achieve the above object, the optical sensor of the present invention obtains energy from a measured voltage or current and outputs an optical signal having a repetition frequency corresponding to the measured voltage or current. It is characterized in that a means for generating, a means for transmitting the optical signal, and a means for receiving the transmitted optical signal and converting the optical signal into an electric signal corresponding to a voltage or current to be measured are provided.

As means for generating this optical signal, a time constant circuit composed of a resistor and a capacitor, a light emitting circuit (element) driven through the time constant circuit, and a charging voltage of a capacitor of the time constant circuit by the light of the light emitting element. A light control switch circuit (element) that discharges can be used. Further, as the light emitting circuit, a circuit in which a light emitting element and a constant voltage element are connected in series is used, and as the light emitting element, elements such as a light emitting diode, a laser diode, an EL element, and a lamp can be used. Further, a Zener diode or a forward voltage of the diode can be used as the constant voltage element.

Further, as the light control switch element,
Elements such as phototransistors and optical thyristors are used, or transistors or field effect transistors (FE) are used.
T) and a photovoltaic element such as a solar cell, a transistor or an FET and a photoconductive element such as CdS, or a transistor or an FET and a photodiode can be used.

Furthermore, as a means for transmitting the optical signal, an optical fiber or optical space propagation can be used. Then, a light receiving circuit (element) and a frequency voltage converter (F / V converter) can be used as means for converting into an electric signal corresponding to the measured voltage or current.

[0010]

[Operation] With the above configuration, the optical sensor of the present invention has a function of converting the measured voltage or current into frequency by using the measured voltage or current as energy, and transmitting the frequency at the light receiving side. It has a function of converting into an electric signal corresponding to the original voltage or current, and has the following effects. (1) The measurement accuracy is not affected by the transmission loss of the optical transmission system because it is transmitted by frequency information instead of amplitude information. (2) The accuracy is the V / F conversion characteristic of the sensor part and the F / V of the light receiving part.
The linearity and gain variation of the light receiving system do not affect the accuracy, depending on the conversion characteristics. (3) Since the energy is obtained from the measured voltage or current, the sensor does not need a power supply. (4) A unidirectional optical transmission system is sufficient, and a bidirectional optical transmission system is not required.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. First, FIG. 1 is a circuit diagram showing an embodiment of the present invention, (a) is a system using an optical fiber OF in an optical transmission system, and (b) is an optical space propagation system using a lens L. 2 is a graph showing the charge / discharge characteristics of the capacitor C shown in FIG.

The input voltage Vi charges the capacitor C through the resistor R, and when the charging voltage of the capacitor C reaches the maximum voltage Vp as shown in (1) of FIG. 2, the light control switch circuit (element) PSW causes the light emitting circuit (element) PSW. It receives the optical signal OPT1 of the element) OS and becomes conductive. Then, in FIG.
As shown in, the capacitor C is discharged, the voltage of the capacitor C becomes the minimum voltage Vb, the optical signal OPT1 suddenly weakens, and the optical control switch circuit (element) PSW becomes non-conductive. Then, the capacitor C is charged again as shown in (1) to (2) of FIG. 2, and the charging / discharging operation is repeated.

Since the charging / discharging frequency depends on the input voltage,
The light signal OPT2 is received by the light receiving circuit (element) OR, and the charging / discharging frequency is output by the frequency voltage converter F / V to the output voltage Vo.
If converted into, the input voltage Vi can be detected from the output voltage Vo.

In the present invention, various variations of the optical control switch circuit (element) PSW in FIG. 1 are conceivable, and for example, a phototransistor PTR is used as shown in FIG. 3A. ,
A transistor TR and a solar cell SC are used as shown in (b), and a transistor TR and Cds are used as shown in (C).
A photoconductive element PR and a resistor Rb may be used, a transistor TR, a photodiode PD and a resistor Rb may be used as shown in FIG.

Further, the light emitting circuit (element) OS in FIG.
There are various possible variations. For example, as shown in FIG. 4A, a light emitting element OD and a constant voltage element RD are used, and as shown in FIG. 4B, a light emitting diode LED and a zener diode ZD are used. Using
The one using only the light emitting element OD as in (C), (d)
As described above, a device using only the laser diode LD can be considered.

The embodiment shown in FIG. 5 is an example using the phototransistor PTR shown in FIG. 3A, the light emitting diode LED and the Zener diode ZD shown in FIG. 4B, and this embodiment is the present invention. 3A, as well as FIG.
Examples of the optical control switch circuit (element) PSW shown in (b), (c) and (d), and (a), (b), and FIG.
By properly combining the embodiments of the light emitting circuit (element) OS shown in (c) and (d), many embodiments are possible.

FIG. 6 is an application example of the present invention, which is an example in which AC current measurement of the power line PL is performed. Current I of power line PL
Is converted into the voltage Vi by the current transformer CT and the rectifier circuit REC, and the output voltage Vo is converted by the system shown in FIG.
Then, the current I of the power line PL can be known from the output voltage Vo.

[0018]

As described in detail above, according to the present invention, the voltage or current to be measured is used as energy to convert the voltage or current to be converted into frequency for optical transmission.
The following effects can be expected. (1) The measurement accuracy is not affected by the transmission loss of the optical transmission system because it is transmitted by frequency information instead of amplitude information. (2) The accuracy is the V / F conversion characteristic of the sensor part and the F / V of the light receiving part.
The linearity and gain variation of the light receiving system do not affect the accuracy, depending on the conversion characteristics. (3) No power supply is required for the sensor section. (4) The transmission system is insulated. (5) A unidirectional optical transmission system is sufficient, and a bidirectional optical transmission system is not required. (6) The sensor can be composed of inexpensive elements. That is, the optical system can be constructed at a lower cost than a voltage sensor using the electro-optical effect (Pockels effect, Kerr effect) or a current sensor using the magneto-optical effect (Faraday effect).

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, (a) is a system using an optical fiber OF in an optical transmission system, and (b) is an optical space propagation system using a lens L.

FIG. 2 is a graph showing charge / discharge characteristics of a capacitor C shown in FIG.

3 is an optical control switch circuit (element) PSW shown in FIG.
Several types of circuit diagrams of (a) are phototransistors PT
R using, transistor (b) using transistor TR and solar cell SC, (C) transistor TR and Cds
A photoconductive element PR and a resistor Rb are used, and (d) is a transistor TR, a photodiode PD, and a resistor Rb.

4A and 4B are circuit diagrams of several types of the light emitting circuit (element) OS shown in FIG. 1, in which (a) uses a light emitting element OD and a constant voltage element RD, and (b) shows a light emitting diode LED and a zener diode ZD. The one used, (C) uses only the light emitting element OD, and (d) uses only the laser diode LD.

5 is a circuit diagram of an embodiment using the phototransistor PTR shown in FIG. 3A, the light emitting diode LED and the Zener diode ZD shown in FIG. 4B.

FIG. 6 is an explanatory diagram showing an application example of the present invention for measuring an alternating current of a power line.

FIG. 7 is an explanatory diagram showing a configuration of a conventional optical sensor.

[Explanation of symbols]

 Vi input voltage Vo output voltage R resistance C capacitor PSW optical control switch circuit (element) OS light emitting circuit (element) OR light receiving circuit (element) F / V frequency voltage converter OF optical fiber L lens OPT1, optical signal PTR phototransistor TR Transistor SC Photovoltaic cell PR Cds and other photoconductive elements Rb Resistance PD Photodiode OD Light emitting element RD Constant voltage element LED Light emitting diode ZD Zener diode LD Laser diode PL Power line CT Current transformer RO Resistance D diode I Current REC Rectifier Co capacitor

Claims (13)

[Claims] 1. A means for obtaining energy from a measured voltage or current to generate an optical signal having a repetition frequency corresponding to the measured voltage or current, a means for transmitting the optical signal, and the transmitted signal. Means for receiving an optical signal and converting it into an electrical signal corresponding to the voltage or current to be measured,
An optical sensor characterized by being provided. 2. As a means for generating the optical signal, a time constant circuit composed of a resistor and a capacitor, a light emitting circuit (element) driven through the time constant circuit, and charging of a capacitor of the time constant circuit by the light of the light emitting element. 2. An optical sensor according to claim 1, wherein an optical control switch circuit (element) for discharging a voltage is used. 3. The photosensor according to claim 2, wherein a circuit in which a light emitting element and a constant voltage element are connected in series is used as the light emitting circuit. 4. A light emitting diode as the light emitting element,
The optical sensor according to claim 1, wherein an element such as a laser diode, an EL element, or a lamp is used. 5. The optical sensor according to claim 3, wherein a Zener diode is used as the constant voltage element. 6. The optical sensor according to claim 3, wherein a forward voltage of a diode is used as the constant voltage element. 7. The optical sensor according to claim 2, wherein an element such as a phototransistor or an optical thyristor is used as the light control switch element. 8. The optical sensor according to claim 2, wherein a transistor or a field effect transistor (FET) and a photovoltaic element such as a solar cell are used as the light control switch element. 9. The optical sensor according to claim 2, wherein a transistor or an FET and a photoconductive element such as CdS are used as the light control switch element. 10. The optical sensor according to claim 2, wherein a transistor or an FET and a photodiode are used as the light control switch element. 11. The optical sensor according to claim 1, wherein an optical fiber is used as a means for transmitting the optical signal. 12. The optical sensor according to claim 1, wherein optical space propagation is used as means for transmitting the optical signal. 13. A light receiving circuit (element) and a frequency-voltage converter (F / V converter) are used as means for converting into an electric signal corresponding to the measured voltage or current. The optical sensor described.