WO2014112398A1

WO2014112398A1 - Electronic weighing device having flow calculation function

Info

Publication number: WO2014112398A1
Application number: PCT/JP2014/050003
Authority: WO
Inventors: 雄二深見
Original assignee: 株式会社エー・アンド・デイ
Priority date: 2013-01-16
Filing date: 2014-01-06
Publication date: 2014-07-24
Also published as: JP2014137250A

Abstract

Provided is an electronic weighing device, such as an electronic balance, having a flow calculation function, which is able to eliminate an error that occurs when the flow is calculated and accurately obtain an exact flow measurement result. An electronic weighing device having a flow calculation function comprises: a load sensor unit (1) which is provided with a weighing table (1a); a clock generation circuit (4) which generates a reference time signal; an A/D conversion unit (2) which converts an analog load signal outputted from the load sensor unit (1) into digital load data every time receiving the reference time signal; an arithmetic processing unit (3) which converts the load data outputted from the A/D conversion unit (2) into a weighed value by performing a correction operation every time receiving the reference time signal, calculates the change amount per unit time of the weighed value, and finds the flow amount; a display unit (6) which displays data such as the weighed value or a flow amount value outputted from the arithmetic processing unit (3); a memory (5) which stores various kinds of data; and an input/output unit which is composed of a key switch unit (7) and an interface unit (8) and to/from which the various kinds of data are inputted/outputted.

Description

Electronic weighing device with flow rate calculation function

The present invention relates to an electronic weighing device such as an electronic balance and an electronic balance, and more particularly to an electronic weighing device having a function of calculating a flow rate of a liquid or a granular material.

Conventionally, when it is desired to accurately measure a minute flow rate, an electronic weighing device, for example, an electronic balance, which is a highly sensitive measuring instrument, is often used. Specifically, for devices such as pumps that transfer liquids, the accuracy and stability of the flow rate are important as the performance of the device, so when measuring the flow rate for checking the performance of the device and adjusting each device. There is. In this case, particularly in a device with a very small flow rate, the flow rate is generally measured using an electronic balance and an external device such as a personal computer connected to the electronic balance.

And the measurement of the flow volume using an electronic balance is generally performed as follows.
First, when measuring the amount to be injected into a container, as shown in FIG. 4, the container is placed on a weighing platform of an electronic balance, and the mass of liquid injected from the tank into the container by a device such as a pump is determined. While the electronic balance is configured to be capable of weighing, an external device such as a personal computer connected to the electronic balance can record the weighing value of the electronic balance at regular intervals (recording interval: Δt). Then, the flow rate is calculated from the change in the mass of the liquid caused by the liquid injection and the recording interval (Δt). Second, when measuring the mass of the liquid discharged from the tank to the container, as shown in FIG. 5, the tank is placed on the weighing platform of the electronic balance, and the liquid in the tank is discharged in the same manner as described above. Calculate the amount.

Here, a specific method of calculating the flow rate by an external device such as a personal computer will be described. First, the external device records the measured value w ₀ at the measurement start time t ₀ . Next, the measurement w ₁ is similarly recorded at time t ₁ after the elapse of the recording interval (Δt) from time t ₀ . In this way, for each recording interval (Delta] t), the time _t _0, t _1, t metric _w 0 when the _{_{_{2 ··· t n, w 1,}}} w constantly records the 2 · · · _{w n} . Then, the flow rate Q _n at time t _n, by a "determined by the difference between the weight value and the previous weight value at that time", that determine the flow rate Q _n from the following equation at a predetermined time t _n it can.
Q _n = (w _n −w _n−1 ) / Δt

In addition, in cell culture and the like, in order to quantify the culture conditions, there are cases where it is desired to control the flow rate to a specified target when a culture solution or a chemical solution is charged into or discharged from the medium. In this case, in the configuration shown in FIG. 6, the current flow rate is obtained by the above-described method, and the flow rate is adjusted from the external device to the pump from the difference between the target flow rate and the current flow rate, so that the target flow rate is obtained. Control is performed.

Furthermore, not only liquids but also electronic balances with high sensitivity are used in measuring the flow rate when cutting out a small amount of powder (Patent Document 1).

JP 2011-58885 A

Conventionally, however, an external device such as a personal computer is time-controlled based on an internal clock (for example, a crystal oscillator), and records the weighing value of the electronic balance at every recording interval (Δt). On the other hand, the electronic balance is also time-controlled based on an internal clock (for example, a crystal oscillator), and updates the measurement every predetermined time and sends a measurement value request signal from an external device. Upon receipt, one of the predetermined measurement values immediately before reception or immediately after reception is sent to the external device. For this reason, it is practically impossible to synchronize the internal clocks of the external device and the electronic balance, and it is not possible to update the weighing in the electronic balance due to the difference between the internal clocks and transmit the weighing value request signal of the external device. There was an inconvenience that the flow rate could not be calculated accurately due to the timing shift.

The cause of this inconvenience is, for example, that the external device records the weighing value of the electronic balance every second (recording interval (Δt = 1 second)), and the updating interval of the weighing value of the electronic balance is 0. The case of 2 seconds (updated 5 times per second) will be described.
The external device performs processing of recording the weighing value of the electronic balance at the recording interval (Δt = 1 second) by the internal clock according to the following procedure.
(1) When the timing of the recording interval is reached, the external device issues a measurement value request signal that is an instruction to output a measurement value to the electronic balance.
(2) The electronic balance outputs the measured value when the measured value is updated next, or sends the measured value that was updated immediately before to the external device, according to the position determined in advance by the measured value request signal. Output to.
(3) The external device records the measurement value output from the electronic balance, and calculates the flow rate from the previously recorded measurement value and the recording interval according to the formula Q _n = (w _n −w _n−1 ) / Δt. Is calculated.

As shown in FIG. 7, the issuance of the weighing value request signal in the above (1) requests the electronic balance to output the weighing value accurately every second, and the updating interval of the weighing value of the electronic balance is If it is exactly 0.2 seconds, the measured value is output to the external device and recorded every time the measured value is updated five times. Therefore, the calculation of the flow rate according to the above formula is always performed correctly.

However, as described above, external devices and electronic balances perform time management based on individual clocks mounted on each device, and it is practically impossible to synchronize both clocks. As long as the clocks of the external device and the electronic balance are not synchronized, in the process of recording the measurement value at regular intervals by the external device, the deviation of the update value of the measurement value of the electronic balance once is several times. It is unavoidable in principle to occur. As a result, even if the actual flow rate is constant, the calculated flow rate changes periodically, making it difficult for the user to use.

For example, if the weight value of the electronic balance is not exactly 0.2 seconds but 0.15 seconds shifted by -5%, the external device weighs every second as shown in FIG. Even if the value request signal is issued, the measurement value update is recorded every 5 times due to a deviation of -5%, and there are cases where the measurement value is recorded every 6 times.
If the measurement value update is recorded 5 times, 0.19 seconds x 5 times = 0.95 seconds If the measurement value update is recorded 6 times, 0.19 seconds x 6 times = 1.14 seconds Thus, the external device cannot detect the change in the measurement value every second, and records the change in the measurement value every 0.95 seconds or every 1.14 seconds. Therefore, the calculated flow rate error is −5% when the update is performed 5 times, and + 14% when the update is performed 6 times.

Conventionally, as a method for reducing the error, two methods have been adopted: firstly, the update interval of the weighing value of the balance is shortened, and secondly, the interval of the measurement value recording by the external device is lengthened. .

That is, according to the first method, even when the external device similarly issues a weighing value request signal every second, the weighing value update interval of the electronic balance is 1 every 0.19 seconds to every 0.019 seconds. When the value is shortened to / 10, the measurement value recorded by the external device may be recorded every 52 times or every 53 times when the measurement value of the electronic balance is updated.

The actual recording interval of the measurement value at this time is 0.019 seconds × 52 times = 0.888 seconds when the update of the measurement value is recorded 52 times, and the update of the measurement value is 53 times. In the case of recording, it is 0.019 seconds × 53 times = 1.007 seconds. Therefore, for the target recording interval of 1 second, the update is -1.2% for 52 times and + 0.7% for 53 times, and the calculated flow rate error is also different from the actual flow rate. It becomes the same. Therefore, by shortening the update interval of the weighing value of the electronic balance, the calculated flow rate error is reduced.

In addition, according to the second method, the measurement value update interval of the electronic balance remains every 0.19 seconds, and the measurement value recording interval (measurement value request signal issuance interval) by the external device is 1 to 10 seconds. If the value is changed to, the weighing value recorded by the external device may be recorded every 52 times or every 53 times when the weighing value of the electronic balance is updated.

The actual measurement interval of the measured value at this time is 0.19 seconds × 52 times = 9.88 seconds when the update is 52 times, and the elapsed time when the number is 53 times is 0. 19 seconds × 53 times = 10.07 seconds. Therefore, for the target recording interval of 10 seconds, the update is -1.2% for 52 times, and + 0.7% for 53 times, and the calculated flow rate error with respect to the actual flow rate. Is the same. Therefore, the error in the calculated flow rate is reduced by increasing the recording interval of the measurement value by the external device.

However, according to the first method, the electronic balance needs to be updated more frequently, and a design that enables high-speed processing is required, leading to an increase in the cost of the electronic balance body. There is an inconvenience. In addition, according to the second method, since the measurement time until the flow rate is calculated becomes long, there is a disadvantage that the response to the actual flow rate change is deteriorated and the detection of the flow rate change is delayed. In addition, both the first and second methods are methods for reducing an error that occurs when the flow rate is calculated, and the error cannot theoretically be completely eliminated.

The present invention eliminates all of these conventional inconveniences, eliminates the problem of error that occurs when calculating the flow rate with an external device in flow measurement using an electronic weighing device such as an electronic balance, and accurately measures the flow rate. An object of the present invention is to provide an electronic weighing device having a flow rate calculation function capable of obtaining a result.

In order to achieve this object, an electronic weighing device having a flow rate calculation function according to claim 1 of the present invention includes a load sensor unit, a clock unit that generates a reference time signal, and a reference time signal from the clock unit. When received, the analog load signal output from the load sensor unit is converted into digital load data, and when the reference time signal is received from the clock unit, the A / D converter outputs the analog load signal. An arithmetic processing unit that corrects load data and converts it to a measured value, calculates the amount of change per unit time of the measured value to obtain a flow rate, and a display unit that displays predetermined data output from the arithmetic processing unit And a storage unit for storing various data necessary for arithmetic processing in the arithmetic processing unit, and an input / output unit for inputting / outputting various data between the arithmetic processing unit and an external device.

According to a second aspect of the present invention, there is provided an electronic measuring apparatus having a flow rate calculation function according to the first aspect, wherein the storage unit is newly converted by a reference time signal from a clock unit in the arithmetic processing unit. The measured value is recorded every time the measured value is updated a predetermined number of times, and the arithmetic processing unit calculates the difference between the measured value previously recorded in the storage unit and the currently recorded measured value for each measured value that is a unit time. The flow rate is obtained by dividing by the recording interval.

Furthermore, in the electronic weighing apparatus having a flow rate calculation function according to claim 3 of the present invention, in the configuration of claim 1 or 2, the predetermined data displayed on the display unit is a measured value and a flow rate value. It is characterized by.

With the above configuration, the load sensor unit of the electronic weighing device outputs an analog load signal to the A / D conversion unit, and the A / D conversion unit is generated at a constant time interval (update interval), that is, at the clock unit. Each time the reference time signal is received, the load signal is digitally converted into load data and output to the arithmetic processing unit. Every time the arithmetic processing unit receives the reference time signal generated by the clock unit, it performs a correction operation on the load data output from the A / D conversion unit to convert it into a measured value, and a unit time of this measured value More specifically, the difference between the measured value recorded last time in the storage unit and the calculated value recorded this time is divided by the recording interval of each calculated value to obtain the flow rate. The measurement value and the flow rate value output from the arithmetic processing unit are displayed on the display unit.

Thus, the arithmetic processing unit mounted on the electronic weighing device has a function of calculating the flow rate from the measured value, and the update interval of the measured value is determined to be unique depending on the design of the electronic weighing device. Specifically, the measurement value update interval is determined depending on the processing based on the reference time from the clock unit made of a crystal oscillator, for example, mounted in the electronic weighing device and the design of the parts, etc. The update interval of the measured value can be obtained based on the accuracy of the logically mounted clock unit. The accuracy of the clock unit is in the order of ppm in the crystal oscillator, and the time error factor in calculating the flow rate is small enough to be ignored. In this way, the calculation of the flow rate that was conventionally performed by an external device such as a personal computer is performed by the electronic weighing device itself, and the flow rate value is displayed on the display unit of the electronic weighing device, or the external flow rate data is displayed. By transmitting this flow rate data from the electronic metering device to an external device when requested by the controller, there is no error due to the reference time not being synchronized, and the flow rate can be accurately calculated.

According to the electronic weighing device according to the inventions of claims 1 and 2 of the present application, it is possible to eliminate an error that occurs at the time of flow rate calculation and to provide an accurate flow rate measurement result with high accuracy. In addition, according to the electronic weighing device according to the invention of claim 3 of the present application, it is possible to visually confirm the accurate measurement value and flow rate value displayed on the display unit.

The block diagram which shows an internal structure at the time of applying this invention to an electronic balance. The schematic block diagram which similarly shows the flow volume calculation state of a liquid. The flowchart which similarly shows processing operation. Schematic which shows the structural example in the case of measuring the injection quantity to the conventional container. Schematic which shows the structural example in the case of measuring the discharge | emission amount to the conventional container. Schematic which shows the example of a structure in the case of performing the conventional flow control. The timing chart which shows the example which the reference time signals of an electronic balance and an external apparatus are synchronizing. The timing chart which shows the example which the reference time signal of an electronic balance and an external apparatus is not synchronizing.

Hereinafter, preferred embodiments of the present invention will be described.
As shown in FIGS. 1 and 2, the electronic balance 10 includes a load sensor unit 1 including a weighing table 1 a on which a container 21 for injecting a liquid to be weighed, an A / D conversion unit 2, and an arithmetic processing unit 3. A clock generation circuit 4 that is a clock unit having a crystal resonator that outputs a reference time signal and an analog load signal output from the load sensor unit 1 are digitally converted into load data every time the reference time signal is received. The load data output from the A / D converter 2 and the A / D converter 2 is converted into a measured value every time a reference time signal is received, and the amount of change per unit time of the measured value is calculated to obtain a flow rate. An arithmetic processing unit 3 composed of a CPU for obtaining the data, a memory 5 that stores various data necessary for arithmetic processing in the arithmetic processing unit 3, a display unit 6 that displays data such as measurement results, and various data Input / output Consisting of radical 19 serving as a key switch unit 7, and the interface unit 8.

Note that in the case where the A / D conversion unit 2 and the arithmetic processing unit 3 have a configuration corresponding to the clock generation circuit 4, it is not necessary to provide the clock generation circuit 4 independently. In addition, commands such as so-called “tare” and “measurement value output” to the electronic balance 10 are performed by the operator via the key switch unit 7, and these command signals are input to the arithmetic processing unit 3. It is processed. Further, when the flow rate value is output to an external device (not shown) such as a personal computer, or the command from the external device is performed via the interface unit 8, these command signals are input to the arithmetic processing unit 3. It is processed. Further, as shown in FIG. 2, the liquid in the tank 22 is injected into the container 21 by a pump 23.

Next, processing operations relating to flow rate calculation performed by the arithmetic processing unit 3 will be described with reference to FIG.
After the initial processing of the arithmetic processing unit 3, the recording interval (T), which is a unit time for calculating the flow rate, is input by the key operation of the key switch unit 7 by the operator (step 101). The measured value update count (m) corresponding to the recording interval and the actual recording interval (Δt) are calculated from the recorded recording interval (T) and the measured value update interval (t _R ) specific to the electronic balance 10. (Step 102). The recording interval (T) may be a rough guide rather than a strict value. For example, when the input recording interval (T) is 1 second and the measurement value update interval (t _R ) is 0.19 seconds, The number of measurement value updates is T / t _R = 5.26... And the measurement value is recorded every five measurement value updates (m = 5). The actual recording interval (Δt) is Δt = t _R × m = 5 times × 0.19 seconds / times = 0.95 seconds. The measurement value update count (m) corresponding to the recording interval and the actual recording interval (Δt) are recorded in the memory 5 for use in later processing.

When the operator operates the pump 23 to start the injection of the liquid to be measured from the tank 22 into the container 21 on the weighing platform 1a, and the flow measurement start instruction signal is input from the key switch unit 7, A flow rate measuring operation is started (step 103).

When the reference time signal from the clock generation circuit 4 is received, the load data output from the A / D converter 2 is corrected and converted into a measured value, and this measured value is updated every time the reference time signal is received. . Metric is updated (step 104), as the first metric _{w 0} at the start of measurement, recorded in the memory 5 (step 105). The counter (hereinafter referred to as CNT) of the arithmetic processing unit 3 adds +1 every time the measured value is updated, and is used to record the measured value every m times of the updated measured value. Is initialized to zero to record the metric value after m times (step 106).

Here, when the operator operates the pump 23 to stop injecting the liquid and inputs the process stop of the flow measurement from the key switch unit 7 to the electronic balance 10 (step 107), the flow measurement ends. (Step 108) On the other hand, if the flow measurement stop instruction is not input, the process is continued.

Metric is updated (step 109), CNT is incremented by one (step 110), the weighing value of the update and reaches m times (step 111), the memory 5 the weight value at that time _{(w i)} (Step 112). This measured value (w _i ) may be displayed on the display unit 6. Since the next measurement value is recorded when the measurement value is updated again m times, the CNT value is cleared to zero (step 113).

Next, the flow rate (Q _i ) is calculated from the previously recorded measurement value (w _i-1 ), the current measurement value (w _i ), and the recording interval (Δt) (step 114), and the calculated flow rate value (Q _i ) Is displayed on the display unit 6 (step 115).

If there is a request to output the flow rate value (Q _i ) to an external device (step 116), the flow rate value is output via the interface unit 8 (step 117). After that, or when there is no request for output of the flow value, the process returns to Step 107, and if the stop of the liquid flow process is not input from the key switch unit 7, the operation from Step 109 to Step 117 is repeated while it is input. The processing operation is terminated (step 108).

The input of the recording interval (T) for calculating the flow rate (see step 101), the flow measurement start instruction (see step 103), and the flow measurement stop instruction (see step 107) are received from the key switch unit 7. Instead of the input, it may be performed by a command from an external device connected to the interface unit 8. In addition, regarding the display of the flow rate on the electronic balance 10, if there is an extra space in the electronic balance 10, a display unit different from the display unit 6 may be provided there, but there is an extra display space. If not, for example, by operating the key switch unit 7 of the electronic balance or a separately provided switching key (not shown), the display unit 6 is temporarily or temporarily replaced with the display unit 6 instead of the original mass display. The flow rate value may be continuously displayed until a switching signal is input. Further, the output of the flow rate from the electronic balance 10 to an external device such as a personal computer may be performed by an output command from the external device or a key operation mounted on the electronic balance 10. Furthermore, if you want to check whether the target flow rate is within the allowable range, set the upper and lower limit values for the target flow rate. When the flow rate exceeds the upper limit value or falls below the lower limit value, a buzzer sound or warning is displayed. If the alarm action is performed, the convenience will be improved.

In addition, in the flowmeter using the electronic balance 10, the measured flow rate is “mass / hour”, but if the liquid can be specified, the mass is converted to the unit of “volume / hour” by correcting the density with the density. It is also possible. As this variation, the density of a plurality of liquids is stored in the memory 5 of the electronic balance 10 in advance, density correction data is read out by selecting the liquid during flow rate measurement, and the flow rate is output in “volume / time” It becomes possible to do.

DESCRIPTION OF SYMBOLS 1 Load sensor part 1a Weighing base 2 A / D conversion part 3 Operation processing part 4 Clock generation circuit 5 Memory 6 Display part 7 Key switch part 8 Interface part 10 Electronic balance 21 Container 22 Tank 23 Pump

Claims

A load sensor unit, a clock unit that generates a reference time signal, and an A / D conversion that converts an analog load signal output from the load sensor unit into digital load data upon receiving a reference time signal from the clock unit And a reference time signal from the clock unit, the load data output from the A / D converter is corrected and converted into a measured value, and a change amount of the measured value per unit time is calculated. An arithmetic processing unit for obtaining a flow rate, a display unit for displaying predetermined data output from the arithmetic processing unit, a storage unit for storing various data necessary for arithmetic processing in the arithmetic processing unit, and the arithmetic processing unit, An electronic weighing device having a flow rate calculation function, comprising: an input / output unit that inputs and outputs various data to and from an external device.
The storage unit records each time a measurement value newly converted by a reference time signal from the clock unit in the arithmetic processing unit is updated a predetermined number of times, and the arithmetic processing unit is recorded in the storage unit last time. 2. The electronic weighing apparatus having a flow rate calculation function according to claim 1, wherein the flow rate is obtained by dividing a difference between the measured value and the currently recorded measured value by a recording interval of each measured value which is a unit time.
3. The electronic weighing apparatus having a flow rate calculation function according to claim 1, wherein the predetermined data displayed on the display unit is a measured value and a flow rate value.