JPH05164774A - Gravitational acceleration measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a gravitational acceleration measuring instrument which can accurately measure gravitation acceleration. CONSTITUTION:A dropping device 101 outputs a start signal and, at the same time, releases an iron ball 108 in response to the operation of a start switch 113 and a noncontact switch circuit 104 outputs a detect signal upon detecting that the iron ball 108 passes through a detection coil 103. A trigger circuit 105 outputs a first trigger signal in response to the start signal and a second trigger signal in response to the detect signal. A timer circuit 106 measures the time until the second trigger signal is generated after the first trigger signal is generated. A personal computer 107 calculates gravitational acceleration based on the distance (an already known value) from the dropping device 101 to the point at which the inductance of the detection coil 103 becomes to have the maximum dynamic value and the time measured by the timer circuit 106.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravitational acceleration measuring device for measuring gravitational acceleration by allowing a magnetic member to fall naturally, and more particularly to a gravitational acceleration measuring device suitable for use in a school laboratory.

[0002]

2. Description of the Related Art Conventionally, a gravitational acceleration measuring device for measuring gravitational acceleration has been used in a school laboratory or the like. In the conventional gravitational acceleration measuring device, first,
An object is allowed to fall freely between two points with a known distance S, and the time T during which the falling object passes between the two points is measured.

Between the distance S and the time T, the gravitational acceleration is G
Then, since there is a relationship of S = 1/2 · G · T ² (1), the gravitational acceleration G is calculated based on the above relational expression.
Is calculated. In the conventional gravitational acceleration measuring device, as a time measuring device for measuring the passing time between two points,
The Boulanger timing machine and Nave's timing machine are used.

[0004]

In the conventional gravitational acceleration measuring device using the Le Boulanger timing machine or Nave's timing machine, many mechanical movable members such as pendulums are used, so that Since the reaction is slow and a large delay time is included, the measurement error is large. Therefore, there is a problem that it is difficult to perform highly accurate measurement.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a gravitational acceleration measuring device capable of measuring gravitational acceleration with high accuracy.

[0006]

A gravity acceleration measuring apparatus according to the present invention comprises a dropping device that opens a magnetic member and outputs a start signal in response to an operation of a start button, and a detection coil through which the magnetic member passes. An oscillation circuit that changes its oscillation state when the magnetic member passes through the detection coil, a detection circuit that detects a change in the oscillation state of the oscillation circuit and outputs a detection signal, and a response circuit to the start signal A trigger circuit that outputs a first trigger signal and outputs a second trigger signal in response to the detection signal; and a timing circuit that starts a clocking operation in response to the first trigger signal and responds to the second trigger signal. And a timer circuit for stopping the time counting operation, a distance from the dropping device to a position where the inductance of the detection coil takes a dynamic extreme value, and the timer circuit It is characterized in that an arithmetic circuit for deriving a gravitational acceleration based on the measurement with time and.

[0007]

The dropping device outputs a start signal in response to the operation of the start button and opens the magnetic member, and the detection circuit changes the oscillation state of the oscillation circuit by passing the dropped magnetic member through the detection coil. That is detected and a detection signal is output. The trigger circuit outputs a first trigger signal in response to the start signal and a second trigger signal in response to the detection signal. The timer circuit measures the time from the generation of the first trigger signal to the generation of the second trigger signal. The arithmetic circuit derives the gravitational acceleration based on the distance from the dropping device to the position where the inductance of the detection coil takes a dynamic extreme value and the time measured by the timer circuit.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a gravitational acceleration measuring apparatus of this embodiment. In FIG. 1, a drop device 101 having an electromagnet iron core 102 and a start button 113 is fixed to the upper part of a support frame 109, and an iron ball 108 as a magnetic member is attracted to the iron core 102 by magnetic force.
Scales 110 for measuring the vertical distance are fixed to the front, rear, left and right of the support frame 109. Support frame 10
A foot 115 with an adjusting screw is attached to the lower part of 9 for keeping the front, rear, left and right scales in the vertical direction by using a spirit level. A rail 111 extending in the vertical direction is fixed to the right side portion of the support frame 109, and a contactless switch circuit 104 is slidably held along the rail 111. The contactless switch circuit 104 includes a detection coil 103.
Are connected, and can be moved in the vertical direction as the contactless switch circuit 104 slides. In addition, the contactless switch circuit 104 includes a fine adjustment knob 112 and an LED.
114 is provided.

The output terminal of the drop device 101 and the output terminal of the contactless switch circuit 104 are respectively a trigger circuit 105.
Is connected to the first input terminal and the second input terminal. The output terminal of the trigger circuit 105 is a personal computer (personal computer) that constitutes an arithmetic circuit via the timer circuit 106.
It is connected to 107. The operation of the gravitational acceleration measuring device configured as described above will be briefly described.

First, as a pre-measurement step, adjustment is performed to prevent the occurrence of a detection error. This is shown in FIG. 2 and FIG.
Will be explained. In FIG. 2, the detection coil 103
Is composed of circular or rectangular coil frames 202 and 204 and a coil winding 203 sandwiched between them. Iron ball hung with thread 201 (the same iron ball as the falling ball) 1
When the lower end of 08 and the upper surface of the coil frame 202 are lowered to the position of the iron ball 108 ₁ and adjusted so that the oscillation of the oscillation circuit is stopped at this position, statically considering the iron ball 108 1. Iron ball 10 whose center is in the center of coil winding 203
It is considered that the inductance becomes maximum at the position of 8 ₂ , that is, the position of L ₁ , and the inductance of the detection coil 103 becomes minimum at the position of the iron ball 108 ₃ where the upper end of the iron ball 108 and the lower surface of the coil frame 204 coincide.

However, as a result of the experiment, as shown in FIG.
As shown in, after adjusting so that the oscillation is stopped at the position of the iron ball 108 ₁ , the iron ball 108 is lowered,
The upper end of the coil frame 204 is slightly smaller than the lower surface X
It has been found that the oscillation resumes when the position of the iron ball 108 _{5 is} lowered (for example, 0.003 m), and the inductance of the detection coil 103 becomes the maximum at the position of the iron ball 108 ₄ , that is, it takes an extreme value. .. That is, it has been discovered that the relationship of FIG. 2 does not hold under the dynamic condition that the iron ball 108 moves in the detection coil, but the relationship of FIG. 3 holds.

From the falling device 101 to the iron ball 1 which is a ferromagnetic material
When 08 passes through the detection coil 103, at which position
Knowing whether the shaking condition changes is also important in terms of measurement accuracy.
This is the most important issue. The position where the oscillation state changes is detected
Dynamics that maximize the inductance of the coil 103
This is the position where the extremum occurs, that is, the position where the Q value is the minimum. this
If the position is considered statically as described above, the detection coil of FIG.
Iron ball 108 located in the middle of Le 103₂Position of L₁of
The position. However, the ferromagnetic iron ball 108
When placed in a magnetic field, electromagnetic induction inside the conductor
There are eddy currents and heat loss of electromagnetic energy.
Magnetization may be delayed due to eddy current or resonance.
Therefore, the iron ball 108 approaches the detection coil 103 and passes through it.
If it goes over, the magnetization will be delayed while being delayed by the external magnetic field.
At the same time, the magnetic field from the iron ball 108 is superimposed on the external magnetic field.
Therefore, the center of the iron ball 108 is located at the position L1 in FIG.
In the state that has reached the state, the state where the magnetization is not most advanced,
Further, it goes to the lower side where the external magnetic field is strong and L₂When
Iron ball 108_FourMagnetization becomes maximum at the position
03 has the maximum inductance, that is, the dynamic extreme value
It Therefore, the inductance of the detection coil 103 is
The position of the maximum iron ball 108, that is, the inductance is dynamic
The position of the iron ball 108, which has such an extreme value, is L₁To L₂Went down
It will be. When the iron ball 108 is further lowered,
The reverse process also proceeds with the same delay, and the iron ball 108 in FIG._FivePosition of
The oscillating operation of the oscillating circuit stops and the LED 114 lights up.
The state will change from the off state. Detection coil 10
Iron ball 108 from the bottom of the lower frame of 3 _FiveThe length of the thread to the upper end is
(L₁-L₂) Is equivalent to.

The above phenomenon is caused by using the pulley to quiet the iron ball 108.
The explanation was given using the case of lowering the
Even if the iron ball 108 falls freely in G, the detection coil 103
The position where the inductance of
Position is position L₂When the center of the iron ball 108 comes to
Iron ball 108_FourThere is no change in the position. Therefore, FIG.
Lower end of the iron core 102 and the iron ball 108 of FIG._FiveThe lower end of
The distance between the
From the value, (A + 2A '+ B + C) (A is the thickness of the winding 203)
Only A'is the thickness of the coil frames 202 and 204, and B is the iron ball 1.
08 ₁And iron ball 108₃Is an iron ball 108₂Length of the part that overlaps with
Sa and iron ball 108_FourIs an iron ball 108_FiveLength of the part that overlaps with
(C is the diameter of the iron ball 108)
Iron ball 108 having maximum maximum or dynamic extreme value_FourUntil
The fall distance S of is calculated.

The operation in the case of performing measurement based on the above principle will be schematically described with reference to FIGS. 1 and 3. First, the contactless switch circuit 104 is moved up and down along the rail 111 to move the detection coil 103 constituted by the coil frames 202 and 204 and the coil winding 203 to a desired position. Then, by using the pulley or the like coupled to the thread 201, iron ball 108 an iron ball and the same dummy iron ball 108 to drop ₁
To the position (the lower end of the iron ball 108 matches the upper surface of the coil frame 202), and in this state, the oscillation circuit (not shown in FIGS. 1 and 3) in the contactless switch circuit 104 oscillates. Fine adjustment knob 11 so that the operation stops just
Rotate 2 to adjust. The stop of the oscillation operation of the oscillation circuit can be confirmed by turning on the LED 114. At the position of the iron ball 108 ₁ , the fine adjustment knob 112 is turned in one direction to turn off the LED 114, and then in the reverse direction until the LED 114 is just turned on. Turn it and adjust. Next, the position of the iron ball 108 ₅ at which the oscillation is restarted (the coil frame 204
The iron ball 108 is lowered to a position (slightly lower than the lower surface part). Resumption of oscillation is confirmed by turning off the LED 114. At this time, the distance L between the lower end of the iron ball 108 _{5 and} the lower end of the iron core 102 is measured by the scale 110.
Iron ball 1 that maximizes the inductance of the detection coil 103
The drop distance S to the position of 08 ₄ is S = L− (A + 2
A '+ B + C).

Since a measurement error may occur due to various factors such as fluctuations in the external magnetic field, the adjustment for stopping the oscillation at the position of the iron ball 108 ₁ and the measurement of the distance L are performed for each measurement. Make sure to prevent measurement errors from occurring. However, the adjustment performed by lowering the iron ball 108 to the position of the iron ball 108 _{5 in} the detection coil 103 is performed by the iron ball 10
It is not necessary to do this every time because it is considered that 8 is magnetized and becomes harmful.

After the above preparation, as shown in FIG. 1, the iron core 108 is attracted to the iron ball 108, and the start button 11 is pressed.
3 is pressed. When the start button 113 is pressed, the iron core 102 loses the attraction force.
8 starts free fall. At the same time, the dropping device 101 outputs a start signal to the first input terminal of the trigger circuit 105 in response to the pressing operation of the start button 113. The trigger circuit 105 outputs a first trigger signal in response to the start signal. The timer circuit 106 starts the time counting operation in response to the first trigger signal.

When the iron ball 108 passes through the detection coil 103, the oscillation of the oscillation circuit stops, and the contactless switch circuit 10
4, the detection signal is output to the second input terminal of the trigger circuit 105. The trigger circuit 105 responds to the detection signal with the second signal.
Output the trigger signal. The timer circuit 106 stops the time counting operation in response to the second trigger signal and completes the measurement of the time T. The personal computer 107 derives the gravitational acceleration G by substituting the distance S and the time T into the equation (1) and displays it on the screen (not shown). This completes the gravitational acceleration measurement operation.

Next, the configuration and operation of this embodiment will be described in detail. FIG. 4 is a detailed block diagram of this embodiment, and the same parts as those in FIG. 1 are designated by the same reference numerals. In the contactless switch circuit 104, the output terminal of the oscillation element 418 that constitutes the oscillation circuit 428 together with the detection coil 103 and the variable resistor 419 has the LED 422 of the photocoupler 421 via the oscillation detector 420 to which the LED 114 is connected.
It is connected to the. Oscillation detector 420 and photo coupler 4
Reference numeral 21 constitutes a detection circuit. The resistance value of the variable resistor 419 is changed by the operation of the fine adjustment knob (112 in FIG. 1), the oscillation is stopped or started, and the oscillation state of the oscillation circuit 428 is changed. The collector terminal of the phototransistor 423 of the photocoupler 423 is connected to the power supply + V _DD ,
The emitter terminal is connected to the Schmitt circuit 426 and also connected to the power supply -V _DD via the resistor 424.

In the trigger circuit 105, the output terminals of the Schmitt circuits 425 and 426 are exclusive NOR circuits 42.
7 to the input terminal of the timer circuit 106. The output terminal of the timer circuit 106 is connected to the input terminal of the personal computer 107. FIG. 5 is a waveform diagram for explaining the operation of the embodiment of FIG. The operation will be described below with reference to FIGS. 1 and 3 to 5. The adjustment before the start of measurement is assumed to be completed as described above.

In FIG. 4, it is assumed that the switches 401, 410 and 412 are in the closed state and the switch 405 is in the open state as the initial state. In this state, each section of the relay 404 is in the position shown in FIG. 4, and the terminals 2 and 5 are connected and the terminals 3 and 6 are connected.
Since the LED 415 is in the light emitting state, the output of the photocoupler 408 is at a high level, and the LED 403 is in the off state. The DC power source 404, the terminal 3 of the relay 404, the terminal 6, the coil 414, and the switch 410 form a closed circuit, and a current flows through the coil 414, so that the iron ball 108 is placed on the iron core 102 as shown in FIG. Assume that it has been adsorbed. Since the oscillation circuit 428 is in the oscillating state, the LED 114 is in the off state and the photocoupler 42 is in the off state.
The output of 1 shall be at a high level.

In this state, when the start switch 405 is closed by pressing the start button (113 in FIG. 1) at time T ₀ , the relay 404
The terminal 5 is connected to the terminal 1, and the terminal 3 is connected to the terminal 7. As a result, the switch 405, the terminal 4, the resistor 4
07, terminal 8, DC power supply 406, switch 401 resistance 4
02, the LED 403 and the terminal 1 form a closed circuit, so that the LED 403 lights up and the start of measurement is displayed. Further, since no current flows through the coil 414, the attraction force to the iron ball 108 disappears and the switch 410,
Since the DC power supply 409, the terminal 3, the terminal 7, the variable resistor 411, the switch 412 and the coil 413 form a closed circuit, a current flows through the coil 413 and a magnetic field that cancels the residual magnetic flux by the coil 414 is generated. As a result, the iron ball 108 can be completely dropped. At the same time, since no current is supplied to the LED 408, the photocoupler 408 is turned off and the photocoupler 408 is turned off.
Output V ₁ of the transition to the low level and the start signal is output to the Schmitt circuit 425.

In response to the start signal, the Schmitt circuit 4
Since the low level signal is output from 25 and the high level signal is output from the Schmitt circuit 426, the exclusive NOR circuit 427 outputs the signal transited from the high level to the low level. The timer circuit 106 starts the time counting operation in response to the signal transiting from the high level to the low level.

When the iron ball 108 falls freely and reaches the position of the iron ball 108 _{1 in} FIG. 3, the oscillation circuit 418 stops oscillating, and when it reaches the position of 108 ₅ , it starts oscillating again. When the position of the iron ball 108 ₄ is reached, the detection coil 10
The inductance of 3 becomes the maximum value, and the photocoupler 42
The output of 1 becomes low level. Therefore, since the Schmitt circuit 426 outputs a low level signal and the Schmitt circuit 425 also outputs a low level signal, the exclusive NOR circuit 427 outputs a signal transiting from a low level to a high level. It The timer circuit 106 is
In response to the signal transiting from the low level to the high level, the time counting operation of the time T is ended.

The personal computer 107 calculates the gravitational acceleration G based on the equation (1) using the distance S and the time T, and displays the calculated value. This completes the measurement operation. By the way, when the fall distance is 0.400m, the set fall distance is 0.001m.
If there is an error of, the fall time will increase by about 3 / 10,000 seconds and the gravitational acceleration should be measured as 9.79 m / s ^2.
It is measured as 9.77m / s ² . When measured using the gravitational acceleration measuring apparatus of this example, the gravitational acceleration could be measured at a value within an average of 9.79 ± 0.015 m / s2.

Since an electromagnet is used in this embodiment, the measurement of the fall distance within 0.2000 m can be performed with high accuracy by lengthening the non-sensing time, but the fall distance is 0.300 m to 0.600m is the best. In the present embodiment, iron balls were used as falling objects, but the present invention is not limited to this, and other magnetic members may be used.

Even when a useless pulse is generated in the vicinity of the detection coil 103, highly accurate measurement can be performed by setting a dead time of about 40 msec. As described above, according to the gravity acceleration measuring device of the present embodiment, the iron ball 10
High accuracy measurement is possible without being affected by the position shift of 8. Moreover, since the free fall time of the iron ball 108 is electrically detected, a measurement error does not occur and highly accurate measurement is possible.

Further, since the two coils 413 and 414 wound in mutually opposite directions are used for the electromagnet for adsorbing and releasing the iron ball 108, hysteresis of the electromagnet does not occur and the iron ball 108 It is possible to freely drop 108, and highly accurate measurement is possible.

[0028]

As described above, according to the present invention, a drop device that opens a magnetic member and outputs a start signal in response to an operation of a start button, and a detection coil through which the magnetic member passes are provided. An oscillating circuit whose oscillating state changes as the magnetic member passes through the detection coil,
A detection circuit that detects a change in the oscillation state of the oscillation circuit and outputs a detection signal; and a first trigger signal that outputs a first trigger signal in response to the start signal and a second trigger signal that outputs a detection signal in response to the detection signal. A trigger circuit for outputting and the first
A timer circuit that starts a timing operation in response to a trigger signal and stops the timing operation in response to the second trigger signal; and a position from the dropping device to a position where the inductance of the detection coil has a dynamic extreme value. Since the arithmetic circuit for deriving the gravitational acceleration based on the distance and the time measured by the timer circuit is provided, the gravitational acceleration can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining the operation of the present invention.

FIG. 3 is an explanatory diagram for explaining the operation of the present invention.

FIG. 4 is a detailed block diagram showing an embodiment of the present invention.

FIG. 5 is a waveform diagram for explaining the operation of the present invention.

[Explanation of symbols]

 101 ... Dropping device 103 ... Detection coil 104 ... Contactless switch circuit 105 ... Trigger circuit 106 ... Timer circuit 107 ... Personal computer as arithmetic circuit 108 ... As magnetic member Iron ball 420 ... Oscillation detector 421 constituting detection circuit 421 ... Photocoupler 428 constituting detection circuit ... Oscillation circuit

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 14, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

From the falling device 101 to the iron ball 1 which is a ferromagnetic material
When 08 passes through the detection coil 103, at which position
Knowing whether the shaking condition changes is also important in terms of measurement accuracy.
This is the most important issue. The position where the oscillation state changes is detected
Dynamics that maximize the inductance of the coil 103
This is the position where the extremum occurs, that is, the position where the Q value is the minimum. this
If the position is considered statically as described above, the detection coil of FIG.
Iron ball 108 located in the middle of Le 103₂Position of L₁of
The position. However, the ferromagnetic iron ball 108
When placed in a magnetic field, electromagnetic induction inside the conductor
There are eddy currents and heat loss of electromagnetic energy.
Magnetization may be delayed due to eddy current or resonance.
Therefore, the iron ball 108 approaches the detection coil 103 and passes through it.
If it goes over, the magnetization will be delayed while being delayed by the external magnetic field.
At the same time, the magnetic field from the iron ball 108 is superimposed on the external magnetic field.
Therefore, the center of the iron ball 108 is located at the position L1 in FIG.
In the state that has reached the state, the state where the magnetization is not most advanced,
Further, it goes to the lower side where the external magnetic field is strong and L₂When
Iron ball 108_FourMagnetization becomes maximum at the position
03 has the maximum inductance, that is, the dynamic extreme value
It Therefore, the inductance of the detection coil 103 is
The position of the maximum iron ball 108, that is, the inductance is dynamic
The position of the iron ball 108, which has such an extreme value, is L₁To L₂Went down
It will be. When the iron ball 108 is further lowered,
The reverse process also proceeds with the same delay, and the iron ball 108 in FIG._FivePosition of
The oscillating operation of the oscillating circuit stops and the LED 114 lights up.
The state will change from the off state. Detection coil 10
Iron ball 108 from the bottom of the lower frame of 3 _FiveThe length of the thread to the upper end is
(L₂-L₁) Is equivalent to.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

Since a measurement error may occur due to various factors such as fluctuations in the external magnetic field, adjustment for stopping the oscillation at the position of the iron ball 108 ₁ is performed for each measurement, and the measurement error is generated. Try to prevent it. However, iron ball 108
The adjustment performed by lowering the inside of the detection coil 103 to the position of the iron ball 108 ₅ is considered to be harmful because the iron ball 108 is magnetized. Therefore, it is not necessary to perform the adjustment every time when the measurement error is large. ..

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (1)

[Claims] 1. A dropping device for releasing a magnetic member and outputting a start signal in response to an operation of a start button,
An oscillation circuit that includes a detection coil through which the magnetic member passes, and an oscillation circuit that changes its oscillation state when the magnetic member passes through the detection coil, and detects that the oscillation state of the oscillation circuit has changed and outputs a detection signal. A detection circuit, a trigger circuit that outputs a first trigger signal in response to the start signal and outputs a second trigger signal in response to the detection signal, and starts a timing operation in response to the first trigger signal. And a timer circuit that stops the timing operation in response to the second trigger signal, a distance from the dropping device to a position where the inductance of the detection coil has a dynamic extreme value, and a time measured by the timer circuit. And a calculation circuit for deriving the gravitational acceleration based on the gravitational acceleration.