JPH0612291B2 - Method and apparatus for automatic measurement of fluid - Google Patents

Description

Description: TECHNICAL FIELD The present invention supplies a fluid such as powder or liquid such as granules from a hopper to a weighing body provided with a transducer, and the weight value thereof is measured by an electric method. The present invention relates to an automatic measuring device for a fluid, which is detected as a signal and sends the weight detection signal to a control device so as to stop the supply from the hopper when a desired weight value is reached.

2. Description of the Related Art Accuracy and speed are required for this type of automatic weighing device. However, the weight detection signal from the transducer fluctuates considerably due to the influence of the vibration of the mechanical system and the movement of the fluid to be measured in the measuring body at the time of measurement, and this fluctuation performs accurate measurement. Will be a big obstacle for. Therefore, in order to ensure the accuracy of weighing, it is necessary to suppress the vibration of the mechanical system that occurs during weighing and the movement of the fluid as the object to be weighed in the weighing body.
In order to carry out such control, it is necessary to reduce the supply amount of the fluid per unit time to reduce the impact degree of the fluid to the weighing body and the movement amount of the weighing body. Doing so impedes swiftness in weighing.

Therefore, in the past, in order to satisfy the above-mentioned contradictory requirements, at the initial stage of the supply of the fluid, the supply amount per unit time is maximized to satisfy the swiftness, and the measured value is the desired final measurement. When the value is close to the value, the supply amount per unit time is reduced to improve the accuracy, while the low-pass
A filter is used to remove fluctuations in the weight detection signal and further improve accuracy. In the present situation, the variation in the weight detection signal is removed by one low-pass filter from the start of supply to the desired final weight value. In this case, in order to perform accurate weighing, it is necessary to select a low-pass filter that is suitable for removing fluctuations near the final weighing value and that has the lowest lower limit of the cut range. A very low-pass filter with a lower limit of 0.5 Hz is used.

Problems to be Solved by the Invention However, when a low-pass filter having an extremely low lower limit of the cut range is used as in the conventional case, the characteristics are such that the supply amount per unit time is large at the initial stage and the middle period ( Especially, it does not match the fluctuation of the weight detection signal that occurs in the initial stage,
As shown in FIG. 4, the delay times TD ₁ and TD ₂ due to the delay in response increase the errors V ₁ and V _{2 in the} measured values. As described above, in the conventional case, since the characteristics of the filter do not match at the initial and middle stages of the supply, a stable weight detection signal cannot be obtained, so that the supply amount based on the weight detection signal cannot be obtained. The control could not be performed responsively, and the time required for one weighing could not be shortened unless the accuracy was sacrificed.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate such drawbacks and to provide an automatic measuring method for a fluid and a device therefor capable of high-speed and highly-accurate measurement.

Means for Solving the Problems A fluid, which is an object to be weighed including granules, is supplied from a hopper equipped with a supply amount control member such as a valve to a weighing body in which a transducer is linked, and the fluid is fed by the transducer. The weight of the fluid supplied to the measuring object is detected as an electric signal, and this weight detection signal is sent to any one of a plurality of low-pass filters with different characteristics to cause fluctuations caused by mechanical system vibrations. After removing the minutes
The weight detection signal from which this variation is removed is digitized by an A / D converter, and the digitized weight detection signal is sent to a control device, and if the digitized weight detection signal corresponds to a preset weighing value, the control is performed. A control signal is issued from the device to control the supply amount of the fluid from the hopper, while selecting one low-pass filter to which the predetermined weight detection signal is to be sent, out of a plurality of low-pass filters having different characteristics. It is an automatic weighing method that controls to do so.

The apparatus used in this automatic weighing method is provided with a supply amount control member such as a valve, a hopper that stores a fluid such as granules, which is an object to be weighed, and the fluid is supplied from this hopper. A measuring body, a transducer which is connected to the measuring body, detects the weight of the fluid supplied to the measuring body and converts it into an electric signal, and a vibration of a mechanical system in the weight detection signal from the transducer. A plurality of low-pass filters with different characteristics, which are selectively selected when the preset fluid weight is reached, in order to eliminate the fluctuations caused by it, and the low-pass filter which eliminates the fluctuations. An A / D conversion device for digitizing the weight detection signal from the filter and a weight detection signal digitized by this A / D conversion device are received, and the weight detection signal is used to detect the weight detection signal. When it is detected that the weighing value set by caulking is reached, a control signal is sent to the supply amount control member of the hopper to control the supply of the fluid from the hopper, and at the same time, the low-pass filters having different characteristics. And a control device for issuing a control signal to make an alternative selection.

Operation By selecting several low pass filters with different characteristics depending on the supplied weight of the fluid,
A low-pass, which is optimally selected in stages for changes in the weight detection signal.
Filters can be used. Therefore, the third
As shown in the figure, the response is improved and the delay time TD
_{Since 1} and TD ₂ are greatly shortened, the errors V ₁ and V _{2 in the} measured values are almost eliminated even at the initial supply and during the middle supply.

Embodiment Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2 of the accompanying drawings.

Here, FIG. 1 is a block diagram showing a configuration of an automatic weighing device with a part omitted, and FIG. 2 is a flowchart of a weighing operation.

First, the structure of the automatic weighing device will be described with reference to FIG.

A hopper 1 in which a fluid, which is an object to be weighed of granules, is housed is provided with a valve 2 which is a supply amount control member, and a weighing body 4 having an opening / closing port 3 which can be opened and closed directly below the hopper 1.
Are arranged. The weighing body 4 is provided with a transducer 5 for detecting the weight of the fluid supplied from the hopper 1 to the weighing body 4 and converting it into an electric signal.
Is supported by an appropriate fixed object via.

The output end of the transducer 5 is connected to the input end of the input amplifier 6, and the weight detection signal output from the transducer 5 is input to the input amplifier 6. The output end of the input amplifier 6 is connected to the input end of an adjuster 7 for performing zero adjustment and gain adjustment for calibrating an indicator (not shown).

The output end of the adjuster 7 is selectively switched by the switcher 8 in order to eliminate the fluctuation of the weight detection signal caused by the vibration of the mechanical system or the movement of the fluid in the weighing body 4. 3 different low pass filters possible 9,10,
11 is connected. Then, the lower limit of the cut range of the low pass filter 9 is 10 Hz, and the low pass filter 1
The lower limit of the cut range of 0 is 5 Hz, low-pass filter 11
The lower limit of the cut area of is set to 0.1 Hz, respectively.

The weight detection signal from which the above-mentioned fluctuations have been removed by the low-pass filters 9, 10 and 11 is sent to the A / D conversion device 12 and digitized, and then the CPU 13 as a control device.
Sent to. C that received the digitized weight detection signal
The PU 13 is configured to send a control signal to the valve 2 of the hopper 1 according to the weight detection signal, open / close the valve 2 to control the supply of the fluid from the hopper 1. Further, the CPU 13 sends a control signal to the switching device 8 when the weight detection signal reaches the preset weight value of the fluid, and controls the low-pass filters 9, 10, 11 to selectively select them. Is configured.

Next, the automatic weighing method of the present invention using the above-mentioned device will be described with reference to FIG. In the present embodiment, the predetermined amount of the fluid to be weighed is set to 50 kg, and the valve 2 is fully opened at the start of the weighing (the flow rate of the fluid from the hopper 1 at this fully opening is 100%), while the low pass is performed.・ When the filter 9 is used and the measured value becomes 35 kg, the valve 2 is throttled to reduce the flow rate to 30%, while the low-pass filter 9 is switched to the low-pass filter 10 and the measured value becomes 45 kg. Valve 2
A description will be given of the case where the flow rate is reduced to 10% by narrowing down the flow rate while the low pass filter 10 is switched to the low pass filter 11 in advance. In addition, in the actual weighing, from the discharge port of the hopper 1 to the weighing body 4
The distance is calculated in consideration of the distance, that is, the head. However, in the present embodiment, it is assumed that the head is ignored and the weighing is performed without considering the head.

Prior to weighing, first, zero adjustment and gain adjustment of the adjuster 7 are performed to perform calibration work. Next, switch the switch 8 so that the low-pass filter 9 operates, and
Fully open the valve 2 of the hopper 1. As a result, the fluid in the hopper 1 is supplied to the weighing body 4 at a flow rate of 100%, and the supplied weight is detected by being converted into an electric signal by the transducer 5. The weight detection signal from the transducer 5 is applied to the vibration of the mechanical system and the weighing body 4
It includes the fluctuation caused by the movement of the fluid inside the chamber. This fluctuation is a characteristic that is compatible with the supply amount when the valve 2 is fully open. The lower limit of the cut range is 10 Hz. The low-pass filter 9 Removed by the A / D converter 12
To be digitized and further sent to the CPU 13.

The weight detection signal from the transducer 5 is 35
When the value corresponding to kg is reached, the control signal is issued from the CPU 13 to the switch 8 and the valve 2, respectively, and the switch 8 causes the low-pass filter 9 to pass the low-pass filter 9.
While being switched to the filter 10, the valve 2 is throttled so that the flow rate becomes 30% and the supply amount of the fluid per unit time is reduced (see FIG. 3). This decrease in the supply amount is compatible with the characteristic of the low-pass filter 10, that is, the lower limit of 5 Hz in the cut region.

The supply of the fluid from the hopper 1 to the weighing body 4 further progresses, and the weight detection signal from the transducer 5 becomes
When the value corresponds to 45 kg, the CPU 1
A control signal is issued from the switch 3 to the switch 8 and the valve 2, respectively.
While switching from 0 to the low-pass filter 11, the valve 2 is also throttled again to bring the flow rate to 10%,
The amount of fluid supply per unit time is further reduced (see Figure 3). The decrease of the supply amount is compatible with the characteristic of the low-pass filter 11, that is, the lower limit of the cut range of 0.1 Hz.

When the weight detection signal from the transducer 5 reaches a value corresponding to a predetermined final weighing value of 50 kg, the CPU 13 issues a control signal to the switch 8 and the valve 2 to close the valve 2 as described above. Then, the supply of the fluid from the hopper 1 to the weighing body 4 is stopped, and one weighing operation is completed.

Then, the fluid of a predetermined weight in the weighing body 4 is stored in a predetermined container when the opening / closing port 3 is opened, and is prepared for the next weighing operation.

The present invention is not limited to the above-described embodiment, and the number of low-pass filters 9, 10, 11 is not limited to three, and the lower limit of the cut range is 10 Hz, 5 Hz for each characteristic. , Not limited to 0.1 Hz.
Further, as the supply amount control member, various configurations such as a plate-shaped shutter can be adopted in addition to the valve 2.

Effects As is apparent from the above description, according to the present invention,
By switching the low-pass filters having different characteristics according to the supply amount of the fluid, it is possible to obtain an effect that an accurate and speedy measuring work can be performed.

[Brief description of drawings]

FIG. 1 shows a preferred embodiment of the present invention, a block diagram showing a part of the structure of an automatic weighing device, FIG. 2 is a flow chart of the same weighing operation, and FIG. FIG. 4 is a graph showing the relationship between the measured weight of the object and the measured time, and FIG. 4 is a graph showing the relationship between the measured weight of the object to be measured and the conventional measuring time. 1 ... Hopper, 2 ... Valve, 4 ... Metering body, 5 ...
Transducer, 8 ... Switch, 9, 10, 1
1 ... Low-pass filter, 13 ... CPU

Claims (2)

[Claims] 1. A fluid, which is an object to be weighed, is supplied from a hopper provided with a supply amount control member to a weighing body linked with a transducer, and the weight of the fluid supplied to the weighing body by the transducer is converted into an electric value. Detected as a signal,
This weight detection signal is sent to any one of a plurality of low-pass filters having different characteristics to remove the fluctuation caused by the vibration of the mechanical system, etc. The D / D converter digitizes and sends the digitized weight detection signal to the controller. When the digitized weight detection signal corresponds to a preset weight value, the controller issues a control signal to output from the hopper. One of the low-pass filters that sends the predetermined weight detection signal among the low-pass filters having different characteristics while controlling the supply amount of the fluid.
A method for automatically measuring a fluid, comprising controlling to select a filter. 2. A hopper provided with a supply amount control member for accommodating a fluid as an object to be weighed, a weighing body to which the fluid is fed from the hopper, and a hopper connected to the weighing body and supplied to the weighing body. A transducer that detects the weight of the fluid being generated and converts it into an electric signal, and a preset amount of the above-mentioned transducer that is set in advance in order to remove a variation caused by vibration of a mechanical system in the weight detection signal from the transducer. A plurality of low-pass filters having different characteristics that are selectively selected when the measured value of the fluid is reached, and an A / D converter that digitizes the weight detection signal from the low-pass filter that eliminates this variation. When the weight detection signal digitized by the A / D converter is received and it is detected by the weight detection signal that the preset weight value is reached, the hopper And a control device for sending a control signal to the supply amount control member of the hopper to control the supply of the fluid from the device, and for issuing a control signal to selectively select the low-pass filters having different characteristics. An automatic metering device for fluids, characterized in that