JPH0472181B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical measuring device that captures a measured quantity such as acceleration as an optical change, and obtains an electrical output proportional to the measured quantity from the change.

Conventional optical measurement devices do not monitor abnormalities in the optical meter (light source, optical transmission line, optical sensor, photoelectric converter, etc.), so even if the light source deteriorates and the output of the measurement device becomes abnormal, I had no idea that it was abnormal. This was particularly problematic when the output of this measuring device was used continuously.

This invention was made to eliminate the drawbacks of the conventional ones as described above, and by constantly monitoring whether the output of the light source and the photoelectric converter are within a certain range, it is possible to detect abnormalities. The purpose of this is to inform the user of the presence or absence of the measurement device and to allow the user to use the measurement device in a normal condition.

An embodiment of the present invention shown in the drawings will be described below. The figure is a configuration diagram showing an embodiment of the optical measuring device according to the present invention, and in the figure, 1 is, for example,
The light source is an LED; 2 is a first detection resistor for detecting the drive current of light source 1; 3 is a first optical fiber for transmitting the light from light source 1; 4 is a device placed in an electric field to be measured. 5 is a second optical fiber for transmitting the light emitted from the optical sensor 4; 6 is a second optical fiber; A photoelectric converter such as a photodiode converts the light from 5 into an electrical signal, 7 is a second detection resistor that detects the output of the photoelectric converter 6, and 8 is the first detection resistor 2.
a first window comparator that generates an output when the output of the second detection resistor 7 is out of the first predetermined range; 9 an average value circuit that obtains the average value of the output of the second detection resistor 7; 11 is an OR circuit that is energized to produce an output when at least one of the first and second window comparators 8 and 10 produces an output, and 12 is an OR circuit that produces an output when An indicator 13 is energized by the output of the OR circuit 11 to indicate that the device is abnormal. This is a processing circuit that produces an output proportional to the measured quantity.

Next, the operation will be explained. The light source 1 emits brightness according to its driving current. Therefore, if the drive current is set to be constant, a constant amount of light will propagate to the first optical fiber 3 and enter the optical sensor 4. The optical sensor 4 is installed, for example, in an electric field, and emits the incident light from the first optical fiber 3 with the intensity changed depending on the voltage as the measured quantity. As the optical sensor 4, there is used an acceleration sensor composed of, for example, a polarizer, a photoelastic element, an analyzer, etc., which emits a certain amount of incident light that is luminance-modulated by vibration acceleration. The light emitted from the optical sensor 4 propagates through the second optical fiber 5 and is irradiated onto the photoelectric converter 6, and the photoelectric converter 6 causes a current corresponding to the irradiated light to flow through the second detection resistor 7. Convert to voltage. The average value of this voltage is determined by an average value circuit 9. Moreover, since the degree of modulation in the optical sensor 4 is constant, the ratio of the AC component of the voltage appearing at the second detection resistor 7 to this average value is determined by the deterioration of the light source 1 and the
The amount of light remains constant even if the amount of light changes due to changes in the propagation loss of the optical fibers 3 and 5. Therefore, by dividing the alternating current component of the voltage appearing at the second detection resistor 7 in the processing circuit 13 by the average value determined by the average value circuit 9, it is possible to always obtain an accurate voltage, which is the measured quantity. .

Next, when the light source 1 or the photoelectric converter 6 is disconnected or shot, the output of the processing circuit 13 becomes an abnormal value. Furthermore, if the light source 1 deteriorates significantly or the propagation loss of the first and second optical fibers 3, 5, etc. becomes abnormally large, the processing circuit 13 cannot compensate and the accuracy deteriorates. Alternatively, the output of the photoelectric converter 6 exceeds the allowable value of the divider in the processing circuit 13 when the amount of light exceeds a predetermined amount, which also deteriorates measurement accuracy. Furthermore, when an excessive current flows through a semiconductor light source or a semiconductor photoelectric converter, the deterioration of these semiconductors is accelerated. Therefore, when the drive current of the light source 1 is converted into a voltage by the first detection resistor 2, and this voltage is outside the first predetermined range (compensable range), the first window comparator 8 is activated. An output is generated, the OR gate 11 is energized, and an abnormality is displayed on the display 12. Also photoelectric converter 6
On the side, if the output of the average value circuit 9 is outside the second predetermined range (compensable range), the second window comparator 8 is energized and produces an output,
The OR gate 11 is energized to display an abnormality on the display 12. That is, the first and second detection resistors 2 and 7
If the light source 1 or the photoelectric converter 6 is disconnected, the voltage appearing on the light source 1 or the photoelectric converter 6 will become zero, and if the light source 1 or the photoelectric converter 6 is shorted, it will become abnormally high. Further, even if the light source 1 deteriorates or the propagation loss becomes abnormally large in the first and second optical fibers 3, 5, etc., the output on the photoelectric converter 6 side will decrease. Therefore,
An abnormality can be detected by detecting that the outputs of the first detection resistor 2 and the average value circuit 9 are outside the first and second predetermined ranges in the first and second window comparators 8 and 10. .

Note that although the above embodiments have described the measurement of voltage, other physical quantities such as temperature may also be measured.

As described above, according to the present invention, by constantly monitoring abnormalities in the optical system, it is possible to obtain reliable and accurate output according to the measured quantity at all times, and when an abnormality occurs, it is possible to display the abnormality. have

[Brief explanation of the drawing]

The figure is a configuration diagram showing an embodiment of an optical measuring device according to the present invention. In the figure, 1 is a light source, 2 is a first detection resistor,
3 is the first optical fiber, 4 is the optical sensor, and 5 is the second optical fiber.
, 6 is a photoelectric converter, 7 is a second detection resistor, 8 is a first window comparator, 9 is an average value circuit, 10 is a second window comparator,
11 is an OR circuit, 12 is a display, and 13 is a processing circuit.

Claims (1)

[Scope of Claims] 1. A semiconductor light source driven by a constant drive current, an optical sensor that receives light from the light source, modulates the intensity of the light according to the amount to be measured, and emits the light, and emits the light emitted from the optical sensor. A semiconductor photoelectric converter receives and converts the emitted light into an electrical signal, and a processing circuit extracts an electrical output corresponding to the measured quantity from the output of the photoelectric converter, and the processing circuit converts the output of the photoelectric converter into an electrical signal. An optical measuring device including an average value circuit for obtaining an average value, and configured to output the electric output by dividing the instantaneous value of the output of the photoelectric converter by the average value of the average value circuit, comprising: driving the light source; A window comparator that determines whether the current value is within a predetermined range, a window comparator that determines whether the average value of the average value circuit is within a predetermined range, and when at least one of these window comparators outputs, the device itself An optical measuring device characterized by comprising means for displaying an abnormality in the.