JPH0454912B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a gravimeter, and particularly relates to a string vibration type gravimeter.

(b) Prior Art Conventionally, weigh scales of this type have a string connected to a rigid support, and this string is installed through a permanent magnet.
A weight is suspended from the bottom end of this string. When a current is passed through this string, an electromotive force is generated because the string is passing through a magnetic field, and this signal is amplified and fed back to the string, causing the string to self-oscillate at a predetermined frequency. do. Gravity G is calculated from the fact that this frequency is proportional to √.

However, in this gravimeter, the string is directly connected to the support, so the number of
It had the disadvantage of having a natural resonance point of 100Hz.
In other words, the rigid support body vibrates due to external factors, and the strings are somehow affected by this vibration.

Therefore, a process to eliminate this resonance is required, and one possible method for this is to separate the string from the rigid support. Therefore, there are devices in which the string is connected to a leaf spring attached to a rigid support, and an electromagnetic damper is attached to the lower part of the weight. This leaf spring forms a low-pass filter, preventing high frequencies from being transmitted to the strings. Further, the electromagnetic damper is made up of a copper ring fixed to a weight and surrounded by permanent magnets, and when the copper ring moves, this movement is suppressed so that vibrations are not transmitted to the strings.

In this gravimeter, the weight is supported by a zero-cross plate spring formed by connecting two plate springs in a cross shape, and supports the weight so that it does not fluctuate.

However, since the tip of the leaf spring to which the string is connected is displaced due to temperature changes, the weight may fluctuate. At this time, a moment is applied to the weight by the zero-cross leaf spring. In other words, the spring force of the zero-cross leaf spring acts to return the weight to its original position, and the tension of the weight acting on the string differs from the actual weight of the weight. With this, there was a problem that accurate gravity G could not be measured.

Conversely, in order to prevent the moment of the zero-cross leaf spring from acting on the weight, the spring force of the zero-cross leaf spring must be made extremely weak. This resulted in insufficient support for the weight, which caused the problem that it could not withstand transportation.

(c) Purpose This invention was made in view of the above points, and it is possible to perform accurate gravity measurement and to prevent the weight from changing even if the leaf spring to which the string is connected is affected by temperature. To provide a gravimeter that allows accurate support.

(d) Configuration In order to achieve the above-mentioned object, the present invention has the following features:
A leaf spring is attached to the support horizontally at its base end, a string is connected to the tip of the leaf spring, the string passes through a magnet, a weight is suspended from the lower end of the string, and a weight is attached to the weight. An electromagnetic damper having a conductor located in a magnetic field is provided, and a stationary holding means for supporting the cone in a stationary state is connected thereto, and a pressing member is provided in contact with the top surface of the tip of the leaf spring, and the pressing member The pressing force of the leaf spring acts on the member within a preset temperature range, and the leaf spring is supported in the horizontal direction by the pressing member against the pressing force of the leaf spring, so that the string The string is made to vibrate by passing an oscillating current through it, and gravity is measured from this frequency.

(e) Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

As shown in FIGS. 1 and 2, reference numeral 1 is a gravimeter of the string vibration type, which measures gravity based on the frequency of the string 2.

The upper end of this string 2 is connected to a leaf spring 3, and a weight 4 is suspended from the lower end. Further, the string 2 is provided through a permanent magnet 5, and the permanent magnet 5 is formed in a substantially U-shape in plan view with a vertical groove 5a, and is attached to a support body 6. In this vertical groove 5a, the string 2
is located vertically across the magnetic field.

The leaf spring 3 has its base end attached to the support body 6, the string 2 connected to its tip end, and extends substantially horizontally. This leaf spring 3 constitutes a low pass filter.

Furthermore, this leaf spring 3 is formed in a shape in which the tip is slightly curved upward in a predetermined temperature atmosphere, and when a preset minute temperature increase change occurs, the leaf spring 3 changes from a curved state to a horizontal state. It is composed of

Above the tip of the leaf spring 3 is a holding member 7 (rigid body).
is attached to the support 6. The lower surface of this holding member 7 is in contact with the tip of the leaf spring 3, and holds the leaf spring 3 in a horizontal state. That is, even if the leaf spring 3 is urged upward in a predetermined temperature state, it is controlled by the pressing member 7 and maintained in a horizontal state, and within a preset temperature change, the leaf spring 3 is always maintained in a horizontal state. It's becoming like that.

An electromagnetic damper 8 is provided below the weight 4, and this electromagnetic damper 8 is composed of a permanent magnet 8a and a copper ring 8b. This permanent magnet 8a
is installed on the support body 6 with a circumferential groove 8c. The copper ring 8b is drilled on the lower surface of the weight 4 and is located in the circumferential groove 8c. When the copper ring 8b moves due to the high vibration of the support 6, this copper ring 8b crosses the magnetic field. Movement is suppressed, and damping of the string 2 is prevented.

Further, a stationary holding means 9 is connected to the weight 4, and this stationary holding means 9 is connected to a zero cross plate spring 9.
The zero-cross leaf spring 9a is composed of two leaf springs connected in a cross shape.
One end of this zero-cross plate spring 9a is attached to the support body 6, and the other end is attached to the weight 4 via a connecting member 9b, so that the weight 4 is supported without any external load acting on it.

Next, the gravity measuring operation of this gravimeter 1 will be explained.

When a current is passed through the string 2 on which the weight 4 is suspended, the string 2 passes through the magnetic field generated by the permanent magnet 5, so
This string 2 will vibrate. Then, this tension is derived as an electric signal, amplified by an amplifier in a feedback circuit (not shown), and then returned to the string 2 and an oscillating current is passed through it, causing the string 2 to self-oscillate at a predetermined frequency.

This oscillation frequency f is expressed by the following equation.

f=1/2√ : Length of string 2 ρ : Linear density M of string 2 : Mass of weight 4 G : Gravitational acceleration Therefore, by finding the frequency f, we can measure the gravitational acceleration G (simply referred to as gravity). .

In this gravimeter 1, even if the instrument itself vibrates at its natural resonance point (for example, several 100 Hz), high frequencies are removed by the leaf spring 3, while low frequencies are removed by the copper ring 8b.
will be suppressed and removed by the movement of string 2.
The resonant frequency for is removed.

On the other hand, although the leaf spring 3 curves upward at a predetermined temperature, it is regulated by the holding member 7 and supported in a horizontal state, and furthermore, the tip does not displace within a preset temperature change. . In other words, upward displacement is regulated by the pressing member 7, while downward displacement only reduces the predetermined upward pressing force and does not occur below the horizontal state. Therefore, the leaf spring 3 is always held in a horizontal state, the weight 4 is always held in a fixed position, and the action of external loads is prevented.

It should be noted that the temperature change allowed by the leaf spring 3 is minute, and any further temperature change is controlled externally of the entire instrument.

Further, although a zero-cross plate spring is used as the stationary holding means 9 in this embodiment, the present invention is not limited to these, and any spring may be used as long as it can support the weight without a load.

(F) Effect As described above, according to the gravimeter of this invention, the leaf spring to which the string is connected does not change due to temperature changes, so the weight does not change, and gravity can be accurately measured from the string's vibration frequency. can be measured. for example,
Since a resolution of several μGAL can be obtained, accuracy can be significantly improved.

Further, since fluctuation of the weight can be prevented while maintaining the function of the leaf spring as a low-pass filter, reliability can be further improved.

Further, when a zero-cross leaf spring is used, the spring force of the leaf spring can be increased, so that the mechanical strength of the meter itself can be increased.

[Brief explanation of the drawing]

The drawings show one embodiment of the invention, and the first
The figure is a schematic side view of the gravimeter, and FIG. 2 is a schematic front view thereof. 1: Gravimeter, 2: String, 3: Leaf spring, 4: Weight,
5: Permanent magnet, 6: Support, 7: Holding member,
8: Electromagnetic damper, 8a: Permanent magnet, 8b: Copper ring, 9: Stationary holding means, 9a: Zero cross plate spring.

Claims (1)

[Scope of Claims] 1. A leaf spring is horizontally attached to the support at its base end, a string is connected to the tip of the leaf spring, the string passes through a magnet, and a weight is suspended from the lower end of the string. An electromagnetic damper having a conductor located in a magnetic field is provided on the weight, and a stationary holding means for supporting the weight in a stationary state is connected to the weight. A member is provided,
A pressing force of a leaf spring acts on this pressing member within a preset temperature range, and the leaf spring is supported in the horizontal direction by the pressing member against the pressing force of the leaf spring, A gravimeter characterized in that an oscillating current is passed through the string to cause the string to vibrate, and gravity is measured from the frequency of the vibration. 2. The gravimeter according to claim 1, wherein the stationary holding means is constituted by a zero cross plate spring formed by connecting two plate springs in a cross shape.