JP2687607B2 - Electromagnetic balance type balance - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronic balance, and more particularly to an electromagnetic force balance type balance.

[Prior Art] A conventional electromagnetic force balance type balance is configured as shown in FIG.

The weighing dish 1 is engaged with the fall-over-preventing Roberval mechanism 2,
The force applied to the weighing dish 1 is applied to the lever 5 via the force point 3. Then, the lever 5 rotates about the fulcrum 4 as a rotation center, the slit 6 at the end moves, and an electric signal is generated in the two photosensors 7 that detect the moving amount and moving direction of the slit 6. This signal is sent to the PID control circuit 1 via the differential amplifier 8.
2 so that the position of the lever 5 returns to the original balanced position, that is, the output of the differential amplifier 8 becomes zero, current flows from the control circuit 12 to the coil 10, and the lever 5 is balanced. Returned to position. This current is simultaneously input to the MPU (Micro Processing Unit) circuit 17 via the amplifier 15 and the AD converter 16 and converted into a load value, and the load value is displayed on the display unit 18.

At this time, the output of the differential amplifier 8 is as shown in FIG. That is, in the equilibrium state where the load on the weighing pan is stable, a large amount of high frequency components having a frequency equal to the natural vibration frequency of the feedback system are generated as shown in FIG. When the load on the pan is gradually increasing, the high frequency component decreases as shown in FIG. 4 (b). Further, when the load on the weighing pan is greatly increased and the differential output is saturated, the state becomes as shown in FIG. 4 (c), and the high frequency components are reduced to the pan.

[Problems to be Solved by the Invention] In a conventional electromagnetic force balance type balance, it takes about 2 to 3 seconds until the lever equilibrium state is obtained. Therefore, use the electromagnetic force balance type balance in a production line or the like. It was practically difficult to obtain an equilibrium state within 1 second and measure a precise mass.

Further, in the equilibrium state in which the load is stable as shown in FIG. 4 (a), the display fluctuates due to the disturbance such as the high frequency component.

The present invention was devised in order to solve the above-mentioned drawbacks of the prior art, and an object thereof is to obtain a balanced state at a high speed and suppress display fluctuation in the balanced state.

[Means for Solving the Problem] In order to achieve the above object, the electromagnetic force balance type balance according to the present invention causes a large amount of high frequency components in the unbalanced output at the time of equilibrium as shown in FIG. In this state, the high frequency component is reduced, and the frequency separation circuit that separates the load unbalanced output into a low frequency component and a high frequency component, and an amplifier whose gain is controlled by the high frequency component from the frequency separation circuit have.

Further, in order to improve the balance of the equilibrium points, another embodiment has a PID control circuit controlled by the high frequency component from the frequency separation circuit.

[Operation] In the electromagnetic force balance type balance configured as described above, the load unbalanced output from the sensor is input to the frequency separation circuit and separated into the high frequency component and the low frequency component, and the low frequency component is controlled by the control circuit and the amplifier. Is input to the coil via the, and the amplification degree of the amplifier is controlled by the high frequency component.

In another embodiment, the low frequency component is input to the PID control circuit, and the high frequency component causes the PID control circuit to operate.
PID allocation is changed.

[Example] An example will be described with reference to Figs. 1 and 2.
Since 1 to 10 are the same as those of the prior art shown in FIG. 3, description thereof will be omitted.

In FIG. 1, the output of the differential amplifier 8 is input to the frequency separation circuit 11 and separated into a low frequency component and a high frequency component. Then, the low frequency component from the frequency separation circuit 11
The control circuit 12 inputs the control current from the PID control circuit 12 to the amplifier 14, and the high frequency component from the frequency separation circuit 11 controls the gain of the amplifier 14 via the rectifier circuit 13. The output of the amplifier 14 is fed back to the coil 10 to return the lever 5 to the balanced position, and the amplifier 15, AD
The load value is input to the MPU circuit 17 via the converter 16 and the load value is displayed on the display unit 18.

As a result, the high frequency component is small as shown in FIG. 4 (b) or (c). In the non-equilibrium state, the amplification degree of the amplifier 14 is large, and it is possible to bring the state of equilibrium closer to the equilibrium state more quickly than in the case of using only a PID circuit. Also, the fourth
In the equilibrium state where there are many high frequency components as shown in FIG. 6A, the amplification degree of the amplifier 14 becomes small, and extra hunting can be suppressed.

In the embodiment shown in FIG. 2, the low frequency component from the frequency separation circuit 11 is input to the PID control circuit 12, and
The high frequency component from the frequency separation circuit 11 is input to the control circuit 19 via the rectifier circuit 13. And by the control circuit 19
When the amplifier 20 of the PID control circuit 12 is controlled and, for example, the high frequency component is small as shown in FIG.
Is increased, and when there are many high-frequency components as shown in FIG. 4 (a), the distribution of PID is changed so as to increase I. As a result, the balance at the equilibrium point can be improved as compared with the case where the amplification degree of the amplifier is changed.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to obtain an equilibrium state of an electromagnetic force balance type balance at high speed and suppress fluctuations of the display unit due to disturbance.

[Brief description of the drawings]

1 is a configuration diagram showing an electromagnetic force balance type balance according to the present invention, FIG. 2 is a configuration diagram showing another embodiment of the present invention, FIG. 3 is a configuration diagram showing a conventional electromagnetic force balance type balance, Figure 4 is the third
It is a wave form diagram which shows the load imbalance output of the electromagnetic force balance type balance of the figure. 1 ... Weighing pan, 2 ... Roberval mechanism, 3 ... Power point, 4
...... Support point, 5 ...... Lever, 6 ...... Slit, 7 ...... Photo sensor, 8 ...... Differential amplifier, 9 ...... Magnet, 10 ...... Coil, 11 ...... Frequency separation circuit, 12 ...... PID control circuit ,13…
… Rectifier circuit, 14 …… Amplifier, 15 …… Amplifier, 16 …… AD converter, 17 …… MPU, 18 …… Display, 19 …… Control circuit, 20
……amplifier

Claims (2)

(57) [Claims] 1. A load balance current required for generating an electromagnetic force for holding a movable coil interlocking with a weighing dish in a static magnetic field and canceling a load applied to the weighing dish is supplied to the movable coil. By holding the weighing pan at a predetermined equilibrium position, and calculating and displaying the value of the load from the value of the load balancing current at this time, in the electromagnetic force balance type balance, the frequency separation circuit to which the load unbalanced output is input. And a control circuit to which the low-frequency component output from the frequency separation circuit is input, and an amplifier whose gain is controlled by the high-frequency component output from the frequency separation circuit as well as the load balancing current from the control circuit is input. Electromagnetic force balance type balance characterized by. 2. A load balancing current required for generating an electromagnetic force for holding a movable coil interlocking with a weighing dish in a static magnetic field and canceling a load applied to the weighing dish is supplied to the movable coil. By holding the weighing pan at a predetermined equilibrium position, and calculating and displaying the value of the load from the value of the load balancing current at this time, in the electromagnetic force balance type balance, the frequency separation circuit to which the load unbalanced output is input. And the low frequency component output from the frequency separation circuit is input, and the PID that outputs the load balancing current
An electromagnetic force balance type balance having a control circuit and a circuit for controlling the operation of the PID control circuit by the high frequency component output from the frequency separation circuit.