JPH09210679A - Servo type clinometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select optimal pair of photoreflectors along with the operating conditions thereof by an arrangement wherein a pair of photoreflectors measure predetermined forward current characteristics and predetermined emitter- collector voltage characteristics. SOLUTION: A measuring unit 20 for photoreflector is loaded with a photoreflector and varies power supply to the phototransistor PT side and infrared light emitting diode PD side and then measures the characteristics of phototransistor PT and infrared light emitting diode PD while varying the distance to a shutter. Characteristics between the distance and collector current IC and characteristics between the distance and collector-emitter voltage VCE are measured for specified forward current IF, power supply voltage VCC and collector resistance RL. Consequently, only a pair of elements operating within an optimal allowable range can be selected by measuring a plurality of photoreflector characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo-type tilt measuring instrument equipped with a sensor for detecting a minute angle, which is used for precision measurement of horizontality and tilt measurement in a wide range of fields such as civil engineering and mechanical engineering. In particular, the present invention relates to selection of elements in consideration of the balance of current and voltage characteristics of a pair of reflective photoreflectors used in a minute angle detection sensor.

[0002]

2. Description of the Related Art Conventionally, in a wide range of fields such as civil engineering and mechanical engineering, precision measurement of horizontality and inclination measurement can be controlled by the same measuring instrument, and direct measurement and measurement on an object to be measured can be performed. There has been a demand for an absolute levelness-guaranteed tilt measuring device that enables remote measurement.

Recently, a servo-type tilt measuring instrument has been developed, and it has excellent characteristics such as higher accuracy than other conventional tilt measuring instruments, relatively simple structure, and less susceptible to an external magnetic field. Therefore, it is considered that it will become the mainstream of the tilt measuring instrument in the future in accordance with the above demand.

One of the most important problems in servo-type inclinometers is the problem of offset or zero change. Generally, when the level or tilt measuring instrument is actually placed in an absolute horizontal state and indicates an angle, the indicated value is called an offset, and the level or tilt measuring instrument is set horizontally and the indicated value is the minimum value. Then, the phenomenon in which the indicated value changes from the previous horizontal time when it is placed horizontally again after being greatly tilted is called zero change.

As shown in FIG. 8, the servo-type tilt measuring instrument having such a property is mainly composed of a moving coil type instrument 2 housed in a shield case 1.
The moving coil type meter 2 is composed of a fixed portion 3 and a movable coil 4, and the fixed portion 3 is fixed in the shield case 1 and has a magnet that generates a constant magnetic field. The movable coil 4 is supported so as to freely rotate.
When a current is applied to the movable coil 4, a torque is generated in the movable coil 4 due to the interaction between the current and the magnetic field.

The magnitude T of this torque is expressed by T = ± A · B · N · Io. Here, A is the area of the movable coil 4, B is the magnetic flux density, N is the number of turns of the movable coil 4, and Io is the magnitude of the current flowing through the movable coil 4.

The movable coil 4 is structured to rotate until the torque T and the torque due to the inclination of the shield case 1 are balanced.

Although not shown, the movable coil 4 is rotatably supported in a pendulum shape by shifting its center of gravity downward by a span band. By thus supporting the movable coil 4 in a pendulum shape, the torque balance in the servo mechanism described later functions and the tilt angle can be measured.

The span band is a thin band strip material made of a platinum-nickel alloy and having a rectangular cross section, and its rotational force is applied by its twisting force.
Compared to the pivot support method, the span band support method
Since there is little backlash and friction, even slight vibrations received by the movable coil 4 can be accurately detected.

Such movable coil 4 has arms 5A and 5A extending in the left-right direction perpendicular to the direction of the span band.
B is provided, and the shutters 6A and 6B are attached to the tips of the arms 5A and 5B with the reflection surfaces facing downward. That is,
When the movable coil 4 rotates, the two shutters 6A and 6B, which are in point symmetric positions with respect to the span band, move up and down in opposite directions.

A pair of reflection type photoreflectors Tra and Trd are fixed at positions facing and facing the two shutters 6A and 6B, respectively.

Reflective photo reflectors Tra and Trd
Converts the forward current IF into infrared and converts this into the shutter 6
Infrared light emitting diode Da that emits light toward A and 6B,
Dd and phototransistors PTa and PTd that receive the infrared light reflected from the shutters 6A and 6B and convert the light into collector current Ic.

Forward current I of the infrared light emitting diodes Da and Dd
If F is constant, infrared light having a constant intensity is emitted, so that the intensity of the infrared light received by the phototransistors PTa and PTd is the same as that of the reflective photoreflectors Tra and Tr.
It changes depending on the distance between d and the shutters 6A and 6B. That is, depending on the magnitude of the collector current Ic of the phototransistors PTa and PTd, the reflection type photoreflector Tr can be obtained.
It has a structure capable of detecting the distances La and Ld between a and Trd and the shutters 6A and 6B.

In assembling this servo type tilt measuring device, the reflection type photo reflectors Tra and Trd are arranged on a substantially circular substrate 7, and supports 8A and 8B are provided from both sides of the substrate 7.
The movable coil type instrument 2 is positioned and attached by. Then, the shutters 6A, 6B and the reflection type photo reflectors Tra, Trd are arranged so that the light emitting surface sides thereof face each other. The moving coil type instrument 2 mounted on the substrate 7
Is completed by mounting it on the base 11 via the base plate 9 and the flange 10, mounting the cover 13 having the receptacle 12 on the top, and covering the shield case 1.

As shown in FIG. 9, the reflection type photoreflectors TRa and TRd thus assembled are in a state of facing the shutters 6A and 6B, and the red light from the infrared light emitting diodes Da and Dd is red. External light shutter 6
Phototransistors PTa and PT by reflecting to A and 6B
send to d. That is, the structure is such that the reflection state of light from the shutters 6A and 6B is electrically converted and fed back.

On the other hand, as shown in FIG. 11, the reflection type photo reflectors Tra and Trd in the assembled servo type tilt measuring device constitute a bridge circuit and the shutter 6 is used.
It operates so as to keep the distance between A and 6B and the reflective photoreflectors TRa and TRd constant.

As shown in FIG. 11, this bridge circuit includes resistors RA and RD and phototransistors PTa and PT.
and the phototransistors PTa and P.
The variable resistance VRE for adjusting the variation of Td is interposed between the phototransistors PTa and PTd. In addition, between the resistor RA and the phototransistor PTa and in series between the resistor RD and the phototransistor PTd, the movable coil L and the variable resistor VRo (about 2 kΩ) are provided.
And a resistor r (980 ohms) and infrared light emitting diodes Dd and Da are connected in series between the resistors RA and RD to the variable terminal of the variable resistor VRE.

The movable coil L is a movable portion of a so-called span band ammeter with its center of gravity displaced, and it has a variable resistance VR.
o is a resistor for extracting the output.

A reflection type photoreflector TR in an inclination measuring device provided with a bridge circuit having such a structure.
As shown in FIG. 9, the relationship between a, TRd and the shutters 6A, 6B is such that the center of gravity M1 of the movable coil L forming the movable part is set to a position lower than the center M2 of the movable part and the pendulum shape is set. It has a hanging structure.

Then, the reflection type photo reflector TRa,
TRd is a reflection type light conversion element in which the phototransistors PTa and PTd and the infrared light emitting diodes Da and Dd are integrally packaged, and a stabilized power supply (12 volt DC) is supplied to the infrared light emitting diodes Da and Dd. Has been done.

If no power is supplied to the tilt measuring device having the bridge circuit, as shown in FIG. 12, when the tilt measuring device itself is tilted to the left, the tilt type photoreflector TRa is used. The distance from the shutter 6A becomes the minimum, and the reflection type photo reflector TRd and the shutter 6B are
The maximum distance between and.

In such a state, when power is supplied to the inclination measuring device having the bridge circuit, as shown in FIG. 13, the infrared light emitting diodes Da and Dd of the reflection type photoreflectors TRa and TRd become red. An external ray is emitted, hits and is reflected by the shutters 6A and 6B, and is fed back into the bases of the phototransistors PTa and PTd to enter. Phototransistors PTa and PT that obtained infrared rays
As shown in FIG. 11, d is the collector-emitter voltage VCE when the incident infrared ray amount is converted into the currents Ia and Id.
a and VCEd are generated and fed back to the moving coil L side. Then, as shown in FIG. 9, the bridge circuit works so as to obtain the distance La on the shutter 6A side and the distance Ld on the shutter 6B side.

The equilibrium conditions in which the distances La and Ld are the same are: voltage VA = VD, collector-emitter voltage VCEa = VCEd, current IA = ID, and current Io = zero ampere in FIG. That is, voltage (VA-VD) = (VCEa-VC
The relationship of Ed) is established.

At a certain angle, the difference between the voltages VA and VD between the terminals of the resistors RA and RD, or the collector-emitter voltage VCE of the two phototransistors PTa and PTd.
The difference between a and VCEd is the output voltage. At the time of inclination, the left side and the right side are normally equal and opposite in polarity, and plus or minus zero is established. Thereby, the shutter 6A,
6B and the reflective photoreflectors Tra and Trd have the same distances La and Ld.

In this way, the infrared rays reflected from the shutters 6A and 6B are converted into electric currents and hooded back while the balance condition of the bridge circuit is established by using the reflective photoreflectors Tra and Trd. The minute displacement angle is detected.

[0026]

However, the servo-type tilt measuring device in the above-described conventional technique is capable of controlling a minute displacement angle by balancing the distance between the pair of reflective photoreflectors and the pair of shutters by the bridge circuit. Since the measurement is performed, variations in current and voltage characteristics of each element forming the bridge circuit, particularly the reflection type photoreflector, have a great influence on the performance of the servo type tilt measuring device.

That is, if the current and voltage characteristics of the reflective photoreflectors on both sides are exactly the same when horizontal, the current Io flowing through the moving coil becomes zero, and an ideal servo-type tilt measuring instrument with zero offset can be obtained. .

When the characteristics of the pair of reflective photoreflectors are different, for example, when the distance from the shutter is the same 0.5 mm, the current Ic of one reflective photoreflector is 6.3 mA and the other reflective photoreflector is the same. Assuming that the current Ic of the photo reflector is 5.6 mA, the current Io flowing through the moving coil when the servo-type tilt measuring device is horizontal.
Will no longer be zero, and thus there will be a so-called offset indicating an angle even though the actual angle is 0 °.

Therefore, the present invention has a problem to be solved in selecting an optimum pair of reflective photoreflector elements for use in a servo-type tilt measuring device.

[0030]

In order to solve the above-mentioned problems, a servo-type tilt measuring device according to the present invention comprises a pair of movable coils which are rotatably supported like a pendulum and which reflect light rays on both left and right sides. A pair of reflective photoreflectors integrally formed with a shutter, an infrared light emitting diode that emits a light beam toward the shutter, and a phototransistor that converts the light beam reflected from the shutter into a current, and the pair of reflective photoreflectors. And a bridge circuit incorporating a phototransistor, the pair of reflective photoreflectors having a predetermined forward current characteristic and a predetermined emitter-collector voltage characteristic which are at least the same or approximately the same. That is, the element is used.

The servo-type tilt measuring device having the above-described structure operates as follows. First, several types of resistors having resistance values are prepared, the following measurements are performed for each of the reflective photoreflector candidate elements, and measurement data is collected.

(1) One load resistor is connected in series to the collector of the phototransistor of the reflection type photoreflector, a constant power supply voltage is applied to this series circuit, and the current of the infrared light emitting diode of the reflection type photoreflector is changed. The current and the voltage of the phototransistor are measured while the distance between the shutter and the shutter is kept constant, and the data on the interval-current characteristic and the interval-voltage characteristic are collected.

(2) Regarding the interval-current characteristic and the interval-voltage characteristic, the measurement of the above (1) is carried out by variously changing the measurement conditions by the combination of the values of the two parameters of the collector resistance and the infrared light emitting diode current. Collect data.

(3) The measurements of (1) and (2) above were carried out for all other candidate elements, and the interval-current characteristic and interval-
Collect data on voltage characteristics and.

(4) Next, measurement data having the same measurement conditions (same load resistance, same infrared light emitting diode current) are compared with each other, and two reflection type photoreflectors whose current characteristics and voltage characteristics are most similar to each other are selected. It is selected as a pair of elements of the servo-type tilt measuring device, and the corresponding measurement conditions (load resistance value, light emitting diode current) are adopted as the operating conditions of the selected reflective photo reflector.

As a criterion for comparison and selection, one having a pair of reflective photoreflectors in which the intervals at which the collector currents of the phototransistors are maximized are substantially equal to each other, or the intervals at which the emitter-collector voltage is a minimum are mutually selected. Two reflective photoreflectors that are approximately equal are selected.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of selecting a reflection type photoreflector attached to a minute angle detecting sensor in a servo type tilt measuring instrument according to the present invention will be described below with reference to the drawings. The structure of the servo-type tilt measuring device and the structure of the bridge circuit are the same as those of the prior art, and therefore the description thereof is omitted.

The reflection type photoreflector is a semiconductor element in which a light emitting element and a light receiving element are packaged in one, and a gallium arsenide (GaAs) infrared light emitting diode and a silicon (S) element.
i) It is composed of a phototransistor. The relative emission spectrum characteristic of this infrared light emitting diode is 900
The wavelength sensitivity characteristic of the phototransistor is an infrared band having a peak value at a wavelength of 900 nm.

As shown in FIG. 6, the inclination measuring device equipped with the pair of reflection type photoreflectors having such a structure has the distances La and Ld if the pair of reflection type photoreflectors Tra and Trd have the same characteristics. = 0.5 mm,
Peak value of forward current IC to infrared light emitting diode is 8m
A, collector-emitter voltage VC of the phototransistor
The peak value of E is in equilibrium at 4V, and both are balanced, which is an ideal state.

However, this is just a theoretical one, and it is not appropriate to accurately match the characteristics of a pair of reflective photoreflectors that are mass-produced because the productivity is alienated. Therefore, it is necessary to select the elements corresponding to the offset and the zero change so that the current-voltage characteristics are matched as much as possible.

For example, when a pair of reflective photoreflectors having different characteristics is mounted, the left reflective photoreflector Tra has a current characteristic of 8 mA and a voltage characteristic of 4 V as shown in FIG. The reflection type photo reflector Trd on the right side has a current characteristic of 6.6 mA and a voltage characteristic of 5.3V.

In the tilt measuring instrument equipped with the reflection type photo reflector having such characteristics, when the shutter is horizontal, the current characteristic is 8 mA for the reflection type photo reflector Tra and the reflection type photo reflector when the intersection of the shutter and the characteristic curve is seen. The reflector Trd is 6.6 mA. Since the bridge circuit cannot be balanced with different values on the left and right, the same value is selected by feedback. In the case shown in FIG. 7, the current value on the reflective photo reflector Tra side is set to 6.
The same value is selected with 5 mA, and the shutter tilts and stands still.

At this time, the operating point a of the current characteristic on the reflective photoreflector Tra side is in the so-called negative feedback region, whereas the current characteristic on the reflective photoreflector Trd side is the operating point b with the peak value e interposed therebetween. Since there are two points c, the point c exists in a so-called inversion region and the polarity is inverted. Since these two operating points b and c are converted into the same value, a zero change occurs between the operating points b and c. The current characteristic of the reflection type photo reflector Tra is 6.5 mA or more.
It will move up to 8 mA and it will be in a runaway state.

In order to avoid such a runaway condition,
In a minute angle detection sensor that maintains balance by a pair of reflection type photoreflectors and a bridge circuit, a pair of reflection type photoreflectors used has the same or similar characteristics to each other, and the operating points b and c are reciprocated. The distance needs to be as small as possible.

First, using a reflection type photoreflector measuring device, as shown below with respect to N candidate elements of the reflection type photoreflector, measurement of interval-current characteristic, interval-
Measure the voltage characteristics.

The reflection type photoreflector measuring device 20 comprises:
As shown in FIG. 1, the phototransistor measuring unit 21 and the infrared light emitting diode measuring unit 22 are connected in parallel, and a power supply VCC (DC12V) is supplied to each of them.

The phototransistor measuring unit 21 has a resistance box RL, a phototransistor PT, and an ammeter for measuring the forward current IC of the phototransistor PT connected in series, and a voltmeter for measuring the collector-emitter voltage VCE is used as the phototransistor. It has a structure in which it is connected in parallel to PT.

The infrared light emitting diode measuring section 22 has a structure in which a fixed resistance R (1 KΩ), a variable resistance VR (100 Ω), an infrared light emitting diode PD, and an ammeter for measuring the forward current IF are connected in series. .

The reflection-type photoreflector measuring device 20 having such a structure is equipped with a reflection-type photoreflector to be measured so that the power supply to the phototransistor PT side is variable and the infrared light emitting diode is used. The characteristics of the phototransistor PT and the infrared light emitting diode PD are measured by varying the power supply to the PD side and changing the distance to a shutter (not shown).

Measuring device 20 for this reflection type photoreflector
As shown in FIG. 2, the characteristics of the reflection type photoreflector mounted on the device have variations depending on the respective elements. A reflection type photoreflector is measured with a forward current IF = 10 mA, a power supply voltage VCC = 12 V, and a collector resistance RL = 1 KΩ. For example, the collector-emitter voltage VCE of the elements A, B, and C is formed with a slightly different U-shaped curve with a valley near the distance of 0.6 mm, and the forward current IC is near the distance of 0.6 mm. The peak-shaped curve is formed slightly differently. In each of the elements A, B and C, a curve is formed with a distance of around 0.6 mm as a boundary.

With respect to this characteristic, as shown in FIG. 3, specific elements are indiscriminately selected and mounted on the reflection type photoreflector measuring device 20, and the resistance RL in the resistance box is 100Ω, 200Ω, 300Ω. , 400Ω, 50
The voltage VCE between the collector current IC and the collector-emitter is measured by changing the value to 0Ω and changing the distance to the shutter (not shown) for each resistance at intervals of 0.05 mm and 0.1 mm.

From the above measurement results, even if the resistance RL is changed to 100Ω, 200Ω, 300Ω, 400Ω, 500Ω, the distance from the shutter is 0.5 mm to 0.7 m.
The collector current IC and the voltage VCE between the collector and emitter change at the boundary of m.

FIG. 4 is a graph showing the characteristics of the elements selected indiscriminately based on the data of the measurement results shown in FIG. 3 above. The collector-emitter voltage VCE near the distance of 0.6 mm is shown in FIG. Is the valley and the graph of the collector current IC is the peak.

Below, 1. 1. Measurement of distance and collector current IC characteristics, and The measurement of the distance and the voltage VCE characteristic between the collector and the emitter will be described.

1. Interval-collector current IC characteristic measurement (see FIG. 4) (1) Collector resistance RL = 500Ω, 700Ω, 1K
Ω and 1.6KΩ are prepared. (2) A collector resistor RL of 500Ω is connected to the collector of the phototransistor of the first element, and a power supply voltage V of 12V is applied between the emitter and the other end of the collector resistor RL.
Connect CC. (3) The forward current IF of the infrared light emitting diode is maintained at 12 mA.

(4) The distance between the reflection type photoreflector and the shutter is changed, and the collector current IC is measured, whereby the collector resistance RL = 500Ω and the forward current IF =
A current characteristic curve under the measurement conditions of 12 mA and power supply voltage VCC = 12 V is obtained. (5) The forward current IF of the infrared light emitting diode is adjusted to 10 mA, and the above measurements (4) and (5) are performed. Collector resistance RL = 500Ω, forward current IF = 10 mA, power supply voltage V
A current characteristic curve with CC = 12V as the measurement condition is obtained.

(6) The forward current IF of the infrared light emitting diode is adjusted to 8 mA, and the above (4) and (5) are measured,
A current characteristic curve is obtained with collector resistance RL = 500Ω, forward current IF = 8 mA, and power supply voltage VCC = 12V as measurement conditions.

(7) Collector resistance RL = 700Ω, 1K
The above (2) to (6) are measured with a resistance of Ω and 1.6 KΩ, and a current characteristic curve under each measurement condition (combination of collector resistance value and infrared light emitting diode current value) is obtained. (8) Perform (2) to (7) for all N elements to obtain current characteristic curves under the respective measurement conditions.

2. Interval-collector-emitter voltage VC
Measurement of E characteristics (see FIG. 4) (1) Collector resistance RL = 1 KΩ, 1.2 KΩ, 1.4
Five types of resistors, KΩ, 1.6KΩ, and 2KΩ are prepared. (2) A collector resistance RL of 1 KΩ is connected to the collector of the phototransistor PT of the first element, and a power supply voltage VCC of 12 V is connected between the emitter and the other end of the collector resistance RL.

(3) Forward current I of infrared light emitting diode PD
Hold F at 12 mA. (4) By changing the distance between the reflective photo reflector and the shutter and measuring the voltage VCE between the collector and the emitter, the collector resistance RL = 1 KΩ and the forward current IF =
A voltage characteristic curve under the measurement conditions of 12 mA and power supply voltage VCC = 12 V is obtained.

(5) The forward current IF of the infrared light emitting diode is adjusted to 10 mA and the measurement of (4) is performed, and the collector resistance RL = 1 KΩ, the forward current IF = 10 mA, and the power supply voltage VCC = 12 V are measured. To obtain the voltage characteristic curve. (6) The forward current IF of the infrared light emitting diode is adjusted to 8 mA, the measurement of (4) is performed, and the collector resistance RL = 1.
A voltage characteristic curve is obtained under the measurement conditions of KΩ, forward current IF = 8 mA, and power supply voltage VCC = 12V.

(7) Collector resistance RL = 1.2 KΩ,
When the above (2) to (6) are performed with load resistances of 1.4 KΩ, 1.6 KΩ, and 2 KΩ, the voltage characteristic curves under the respective measurement conditions are obtained. (8) The steps (2) to (7) are performed for all the N elements to obtain voltage characteristic curves under the respective measurement conditions.

3. Selection of Optimal Pair of Reflective Photoreflectors Next, the current characteristic curve and the voltage characteristic curve obtained as described above are measured under the same measurement conditions (the value of the same collector resistance RL and the value of the same forward current IF). Put together.

When the characteristics of the plurality of reflective photoreflectors are measured in this way, it is appropriate that the distances La and Ld between the shutter and the reflective photoreflector are 0.6 mm.
The peak value of the forward-current IC and the voltage VCE between the collector and the emitter, which are limited to the distances La and Ld = 0.6 mm, are measured. Exclude those whose peak value is too low, and use only the elements that are within a certain allowable range.

[0065]

As described above, according to the servo-type tilt measuring device of the present invention, an optimum pair of parts having many variations in characteristics is manufactured when the servo-type tilt measuring device is manufactured. It is possible to obtain the reflection type photoreflector and its usage conditions, and thus it is possible to realize a high-performance minute angle detection sensor in which the zero change is extremely reduced.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a measuring device for a reflective photoreflector according to the present invention.

FIG. 2 is a schematic graph showing variation characteristics of the reflective photoreflector.

FIG. 3 is a graph showing distance characteristics in which the resistance value of the resistance RL in the measuring instrument shown in FIG. 1 is changed.

FIG. 4 is a collector resistance RL in the measuring instrument shown in FIG.
5 is a graph showing current and voltage characteristics with different resistance values.

FIG. 5 is a graph showing current and voltage characteristics of the measuring instrument shown in FIG. 1 when the forward current of the infrared light emitting diode is changed.

FIG. 6 is an explanatory diagram showing a distance relationship between a pair of reflective photoreflectors and shutters having the same characteristics.

FIG. 7 is an explanatory diagram showing a distance relationship between a pair of reflective photoreflectors having different characteristics and a shutter.

FIG. 8 is an exploded perspective view showing the structure of a servo-type tilt measuring device.

FIG. 9 is an explanatory diagram showing an enlarged distance relationship between a shutter and a photo reflector.

FIG. 10 is a basic configuration diagram of a servo-type tilt sensor.

FIG. 11 is an explanatory diagram showing a torque balance type bridge circuit.

FIG. 12 is an explanatory diagram showing a relationship between a reflective photoreflector and a shutter.

FIG. 13 is an explanatory diagram showing a relationship between a reflective photoreflector and a shutter.

[Explanation of symbols]

 1 Shield Case 2 Moving Coil Type Instrument 3 Fixed Part 4 Moving Coil 5A, 5B Arms 6A, 6B Shutter 7 Substrate 8A, 8B Support 9 Base Plate 10 Flange 11 Unit 12 Receptacle 13 Cover 20 Reflective Photoreflector Measuring Instrument 21 Phototransistor Measuring unit 22 Infrared light emitting diode Measuring unit Tra, Trd Reflective photoreflector IF Forward current Da, Dd Infrared light emitting diode Ic Collector current PTa, PTd Phototransistor La, Ld Interval RA, RD resistance VRE Variable resistance L Moving coil VRo Variable resistance r Resistance M1 Heavy core M2 Middle core Ia, Id, Io, IC current VCEa, VCEd Collector-emitter voltage VA, VD voltage RL resistance (resistor box) R fixed resistance VR variable resistance

Claims (1)

[Claims] 1. A pair of shutters for reflecting light rays to the left and right sides of a movable coil rotatably supported in a pendulum shape, an infrared light emitting diode for emitting light rays in the shutter direction, and a light ray reflected from the shutter. A servo-type tilt measuring instrument comprising a pair of reflective photoreflectors integrally formed with a phototransistor for converting into electric current, and a bridge circuit incorporating the phototransistor of the pair of reflective photoreflectors, wherein The reflection type photoreflector is a servo-type tilt measuring device characterized in that a predetermined forward current characteristic and a predetermined emitter-collector voltage characteristic are at least the same or approximately the same.