JPH0430494Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention relates to an inclinometer, particularly an inclinometer that has a wide measurement range and can perform highly accurate measurements.

(b) Conventional technology Conventionally, for example, in order to predict earthquakes, small displacements caused by plate movement on the ocean floor are detected as inclinations.
Inclinometers are often used in which a high-sensitivity magnetic sensor, such as a flux gate, is suspended inside a box via a gimbal mechanism.

(c) Problems that the invention aims to solve The conventional inclinometers mentioned above use high-sensitivity magnetic sensors such as flux gates, so accurate measurements are possible; however, they use a gimbal mechanism. However, there was a problem that the initial tilt angle at the time of equipment installation was limited, and a wide measurement range could not be obtained.

In view of the above, the purpose of this invention is to provide an inclinometer with high accuracy and a wide measurement range.

(d) Means for Solving the Problems The inclinometer of this invention has leaf springs 4 and 5 which are erected with their lower ends attached to the fixed part 1, and whose upper ends are connected to the upper ends of the leaf springs. Then, the base shaft 3, the weight 6 provided on the base shaft, a pair of strings 9 and 10 symmetrically supported and tensioned between the lower end of the base shaft and the fixed part, and a first string including each of the pair of strings individually. and second oscillation sections 13, 14, and output circuit means 15, 16, 17 for deriving a signal according to the difference in oscillation frequency between the first and second oscillation sections.

(E) Effect In this inclinometer, when the base, that is, the fixed part, tilts, the base axis also tilts accordingly, and the weight creates ± tension on the pair of strings, which causes a difference between the first and second oscillation frequencies. arise. This frequency difference is proportional to the tilt angle θ. Therefore, by deriving a signal according to the oscillation frequency difference using the output circuit means,
The tilt angle θ can be detected. The leaf spring maintains the base shaft in the center of the pair of strings even when the instrument body is tilted, and also protects the strings from breaking when excessive tension is applied to them.

(f) Examples This invention will be explained in more detail with the following examples.

As shown in FIGS. 1 and 2, an inclinometer according to an embodiment of this invention has a base 2 supported by a fixed part 1 formed integrally with a case (not shown), and a band plate attached to the base 2. The base shaft 3 of the shape is inserted, and the base 2
A pair of leaf springs 4 and 5 are erected at both ends of the base 2, and the lower ends thereof are connected to each other, and the upper end of the base shaft 3 is connected to the upper ends of the leaf springs 4 and 5. Further, a weight 6 is provided at the lower end of the base shaft 3, a hole 7 is provided in the center of the base shaft 3, and a permanent magnet 8 is fitted into the hole 7. Furthermore, a pair of strings 9 and 10 are stretched between the base 2 and the weight 6 on the front and back sides of the plate surface of the base shaft 3, spaced apart from the base shaft 3.

Although not shown in FIGS. 1 and 2, both ends of the strings 9 and 10 are connected to respective oscillator circuits, so that current flows through the strings 9 and 10, respectively.

This oscillator utilizes the principle of a string gravimeter, and the principle of the string gravimeter will be explained below. When a weight is suspended under a thin string, the frequency f of its transverse vibration is given by f=SQR(F/σ)/(2L). In addition, F is the tension of the string, L is the length of the string, and σ
is the linear density of the string, and SQR is the root symbol.

When a permanent magnet or the like is used to apply a direct current magnetic field perpendicular to the string on which a weight is suspended, a voltage is generated at both ends of the string due to this magnetic field and the vibration of the string. When amplified by an amplifier and the amplified output is fed back positively to both ends of the string, this system will oscillate at the string's natural frequency.

The circuit section of the inclinometer shown in FIG. 3 utilizes the principle of this string gravimeter, and the strings 9 and 10 are
Oscillator 11, 1 consisting of an amplifier circuit and a positive feedback circuit
2, and constitute string oscillation sections 13 and 14 as a whole. Therefore, the string oscillator 13 oscillates at a natural frequency f ₁ determined by the tension of the string 9, and the string oscillator 14 oscillates at a natural frequency f ₂ determined by the tension of the string 10.

Frequencies f ₁ and f ₂ from oscillator 11 and oscillator 12
The oscillation signals are applied to frequency-voltage converters 15 and 16, and converted into voltages corresponding to each frequency.
The output voltages of the frequency-voltage converters 15 and 16 are further input to a differential amplifier 17, which derives a signal corresponding to the difference between the two voltages, that is, the frequency difference between the output signals of the oscillators 11 and 12. There is.

Next, the principle and operation of the inclinometer according to the above embodiment will be explained.

Example If the length of the strings 9 and 10 of the inclinometer is 2M and the weight of the weight 6 is 2M, and the base 2 is tilted by θ in the direction including the strings 9 and 10 as shown in FIG. 6, a tension of Mgcosθ+Mgsinθ...A/Z is generated in the string 9, and a tension of Mgcosθ−Mgsinθ··A/Z is generated in the string 10.

The second term in the above equation is expressed as follows: bending moment M _b , tension T, cross-sectional area A of the string, and section modulus Z of the string are T=M _b ×A/Z=M×g×SINθ××A/Z. I took advantage of being in a relationship.

As the inclinometer is tilted by θ, the tension of the strings 9 and 10 changes as described above, so the oscillation frequencies f ₁ and f ₂ of the string oscillation units 13 and 14 are f ₁ = 1/ 2√σ√＋・
・Z Also, using Maclaurin's expansion formula, f ₁ ≒√Mgcosθ/2√σ[1+1/2・sinθ・・
A/cosθ・Z −1/8 (sinθ・・A/cosθ・Z) ² 〕 f ₂ = 1/2√σ√−・
・Z Approximating in the same way as the previous equation, f ₂ ≒√Mgcosθ/2√σ[1-1/2・sinθ・・
A/cosθ・Z −1/8 (sinθ・・A/cosθ・Z) ² ] However, g: gravitational acceleration, σ: linear density of the string A: cross-sectional area of the string, Z: section modulus of the string b: Width, h: Can be expressed by the thickness of the string. Therefore, finding the difference f ₁ − _{f 2} between both frequencies, f ₁ − f ₂ =√Mgcosθ・sinθ・・A/2√σ・cos
θ・Z, and from this formula, tanθ√=2Z√σ(f ₁ − f ₂ )/A√Mg Here, strings 9 and 10 use rectangular splits with cross-sectional area A of b x h. , the section modulus Z is Z
= bh ² /6 = hA/6.

Therefore, the relationship of Z/A=h/6 and COS≒1
Using the approximation formula of tanθ≒θ, θ=h√σ(f ₁ −f ₂ )/3√Mg. If we set h√/3√=K (constant) here, then θ=K(f ₁ −f ₂ ). Therefore, from this, the vibration frequency of strings 9 and 10
By measuring f ₁ and f ₂ , the inclination angle θ of the base 2 can be determined. The leaf springs 4, 5 hold the base shaft 3 in the center of the strings 9, 10 even if the instrument body is tilted, and protect the strings 9, 10 from breaking when excessive tension is applied to them.
Note that the reaction force of the leaf springs 4 and 5 is the chord 9 and 1 due to the inclination.
It is designed so that there is no problem with tension changes of 0.

In this example inclinometer, the oscillating units 13 and 14 are caused to oscillate at frequencies f ₁ and f ₂ , and the frequencies f ₁ and f ₂ are converted into voltages by frequency-voltage converters 15 and 16, and the difference voltage is The voltage is obtained from the output of the dynamic amplifier 17, and a voltage corresponding to the tilt angle θ is derived from the differential amplifier 17.

In the above embodiment, a frequency-voltage converter is used to obtain a signal corresponding to the difference in the oscillation frequencies of the oscillation sections 13 and 14, but a counter and a subtracter may also be used.

(g) Effects of the invention According to the inclinometer of this invention, mechanically,
Since there are no mechanical friction parts, highly accurate measurements can be performed.

Furthermore, since the amount of movement of the string, weight, etc. due to inclination is minute, a wide range of initial inclination angles can be tolerated when installing the device, and a wide measurement range can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a front view of the essential parts of an inclinometer showing an embodiment of this invention, Fig. 2 is a side sectional view of the inclinometer, Fig. 3 is a circuit block diagram of the inclinometer, and Fig. 4 is a , is a side view for explaining the operation of the inclinometer. 1... Fixed part, 2... Base, 3... Base shaft,
4, 5...plate spring, 6...weight, 8...permanent magnet,
9, 10... string, 13, 14... oscillation section, 15,
16... Frequency-voltage converter, 17... Differential amplifier.

Claims (1)

[Scope of utility model registration request] A leaf spring whose lower end is attached to a fixed part and stands upright; a base shaft whose upper end is connected to the upper end of the leaf spring; a weight provided at the tip of the base shaft; and a lower end of the base shaft and the fixed part. A pair of strings supported and stretched symmetrically between them, a first and a second oscillating section that individually include the pair of strings, and a oscillating section that responds to the difference in oscillation frequency between the first and second oscillating sections. and output circuit means for deriving a signal.