JPH0230456B2 - DENSHICHINKOTENBIN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sedimentation balance for measuring the particle size distribution of powders.

One method to measure the particle size distribution of powder is
The sedimentation balance method based on Stokes' law has been used for a long time. In conventional sedimentation balances, the completion of sedimentation of the sample is determined by drawing a sedimentation curve on recording paper, etc., based on the weight of the sample uniformly stirred in the medium and deposited on the sedimentation plate, and the elapsed time after the start of sedimentation. Analysis work was required to calculate the particle size distribution by calculating the sedimentation rate, etc., based on the sedimentation weight at the time the sedimentation was completed. Furthermore, changes in the recording time due to differences in the sedimentation speed of the sample to be measured are limited to a few steps depending on the feeding speed of the recording paper, which has the disadvantage that it may be difficult to decipher it during subsequent analysis. There is.

The present invention has been made in view of the above, and an object of the present invention is to provide an electronic sedimentation balance that can display elapsed time, sedimentation rate, etc. every moment during sedimentation without waiting for the completion of sedimentation.

A feature of the present invention is that the weight of the sample powder in the air is converted into the weight in the medium and stored, and at the same time the sample powder is diffused into the medium and a measurement start signal is issued, it is transferred to the sedimentation dish. The sedimentation rate is calculated by dividing the sedimentation weight by the above-mentioned converted weight of the sample in the medium, and the sedimentation rate is displayed moment by moment along with the elapsed time after the generation of the measurement start signal. Furthermore, by converting the above-mentioned elapsed time into particle size using Stokes' equation, the deposition rate for a given particle size,
It is possible to display the rate of change in sedimentation, etc.

Embodiments of the present invention will be described below based on the drawings.

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

The load detection unit 1 is provided with a weighing pan 2 and a settling dish 4 suspended from a lower hook 3 provided on the same line of load action as the weighing pan 2. 2 and settling plate 4 are detected, converted into digital signals at predetermined intervals, for example, every 0.2 seconds, and outputted to the control unit 5. The settling dish 4 is submerged in a settling container 6 filled with a medium, and a container 7 for containing sample powder is placed on the weighing dish 2. In this state, the load detection unit 1 is The output is set to 0. The control unit 5 is composed of a microprocessor, which includes a central processing unit CPU that executes processing programs and various calculations and controls each peripheral device, a read-only memory ROM that stores processing programs, and digital conversion from load detection 1. It consists of a random access memory RAM, etc., which has areas for storing data and areas for various registers, and these are connected to each other by bus lines. The control unit 5 includes a control unit 5
A display 8 for displaying elapsed time, sedimentation rate, rate of change in sedimentation, particle size, etc. based on commands from the controller, a keyboard 9 equipped with various operation keys such as a tare key, a numeric keypad for setting initial conditions, etc. are connected. has been done.

Next, the operation of the embodiment of the present invention will be explained along with the method of use.

FIGS. 2a and 2b are flowcharts showing a processing program according to an embodiment of the present invention.

First, prior to measurement, various constants such as sample density ρf, medium density ρs, medium viscosity η, etc. are input from the keyboard 9 (ST1). next,
When a desired weight of sample powder is placed in the container 7 on the weighing pan 2, the digital conversion data from the load detection section 1 becomes a value corresponding to the weight and is sent to the random access memory RAM of the control section 5 at predetermined intervals. be taken in. The random access memory RAM has a maximum of n+1 data storage areas, and every time the latest data _d0 is taken in, the oldest data dn is discarded (ST2, ST3). random access memory
Among the data taken into the RAM, an average value W ₀ is calculated from the latest i pieces of data (for example, 3 pieces) and displayed on the display 8 (ST5, ST8, ST9).
In this way, when the sample powder to be measured is placed on the weighing pan 2, its weight (in air) is displayed every moment. In this state, if you press the 100% key on the keyboard 9, the average value W ₀ (sample weight in air) is determined by the following equation (1) using the sample and medium density ρf and ρs. The sample weight Wd in the medium is converted and stored in the deposition amount register, and the deposition rate Q ₀ is calculated by the following equation (2) (ST7, ST10). And Wd=W ₀ ×ρf−ρs/ρf……(1) Q ₀ =Wd/Wd×100%……(2) In this case, the deposition rate Q ₀ is 100% and above the weighing pan 2 In order to confirm that the weight Wd of the sample placed in the medium is the maximum deposition amount, the value
100% is displayed on the display 8, and the 100% key ON flag is set (ST11, ST9). After 100% is displayed, when the sample powder in the container 7 on the weighing pan 2 is uniformly dispersed into the medium in the sedimentation container 6 and the tare key is pressed, the load detection unit 1 at that point is
The average value W ₀ of the output from the tare weight register is stored as the tare weight amount t, and at the same time, tare weight subtraction processing is performed. The deposition rate Q ₀ is calculated by dividing the tared average value W ₀ by the above-mentioned Wd (ST6, ST12, ST13). Pressing this tare key means a command to start sedimentation measurement of the sample powder dispersed in the medium, and the calculated sedimentation rate Q ₀ and
The elapsed time of 0 seconds is displayed on the display 8, and
Set the tare subtraction ON flag and reset the 100% key flag (ST14). Deposition rate at this point
Q ₀ is the average value W ₀ after tare processing is 0, so
Of course it is 0%. As time passes, particles with larger diameters start to be deposited in the sedimentation pan 4, but after the tare subtraction key is pressed, the detection data d ₀ output from the load detection unit 1 at predetermined intervals is equal to the tare weight described above. The tare weight is subtracted by the amount t (ST15), and the counter S
is incremented by one count (ST16). The tared data d ₀ is the weight of the sample powder deposited in the sedimentation dish 4 in the medium, and the sedimentation rate Q ₀ is calculated by dividing this value by Wd (ST17). Then, the unit for displaying the elapsed time on the display 8 is selected in accordance with the deposition rate Q ₀ when the value of the counter S reaches 5, that is, when 1 second has elapsed after the start of the measurement. For example, if the deposition rate Q ₀ at that point is 1% or more, 1
The optimal time display unit is selected according to the sedimentation speed of the sample, such as seconds, 10 seconds for 0.1 seconds or more and less than 1 second, and 1 minute units for less than 0.1 seconds, and S ₀ according to the selection. , S ₁ and M flags are set (ST22, ST23, ST24, ST25, ST26,
ST27). Thereafter, the elapsed time and deposition rate Q ₀ in that time unit are displayed moment by moment on the display 8 (ST30,
ST35). Detection of the elapsed time T is based on the counter S that is incremented by 1 every time data is captured (every 0.2 seconds), and if 1 second is selected as the display time unit, the counter S reaches 5. Each time, the counter S0 is reset to 0, the counter _S0 is incremented by 1, and the value of the counter _S0 is displayed on the display 8 (ST19, ST36, ST37).
If seconds or 1 minute are selected, counter S will be 50.
Or, each time it reaches 300, reset the counter S to 0 and increase the counter _S1 or M by 1,
The value of the counter _S1 or M is displayed on the display 8 (ST20, ST40, ST41, ST21, ST44, ST45).
If 1 second or 10 seconds is selected as the display time unit, the counter _S0 or _S1 is reset to 0 every time the elapsed time reaches 60 seconds, and the minute counter M is counted by 1. Up (ST38,
ST39, ST42, ST43). A state in which the elapsed time T and the deposition rate Q ₀ are displayed on the display 8 is shown in FIG. 3a. In Figure 3a, the elapsed time after the start of sedimentation is 9 minutes and 53 seconds, and the sedimentation rate at that time is 86.2%.
It is displayed that it is. In this way, while the elapsed time T and the deposition rate Q ₀ are displayed moment by moment, the elapsed time T is calculated as shown below derived from Stokes' equation.
It is converted to the sedimented particle diameter Dj using equation (3) (ST47).

Dj=√K/T……(3) However, K=18ηH/g (ρf−ρs) H: Distance from the medium liquid level to the sedimentation plate g: Acceleration of gravity And, the value of the particle diameter Dj is determined in advance. When the set value reaches an integer multiple of an arbitrary value such as 0.1 μm, 0.15 μm, 0.2 μm, etc., or its vicinity,
From the deposition rate Q ₀ at that point, subtract the deposition rate Q ₁ at the time when the set particle size is reached immediately before,
The sedimentation change rate ΔQ ₀ is calculated. Then, the above-mentioned deposition rate _Q0 is stored in the first deposition rate register, and the first display pass flag is set (ST48,
ST49). Note that the previous deposition rate Q ₁ is stored in the first deposition rate register when the particle diameter Dj reaches the previous set value, and if the particle diameter Dj reaches the set value for the first time, the previous deposition rate Q ₁ is stored in the first deposition rate register. The value is 0. The calculated particle diameter Dj and deposition rate Q ₀ are displayed for 1 second together with auxiliary display symbols (ST29, ST50, ST31, ST32,
(ST33, ST34, ST51, ST35, ST52, ST53), Dj and deposition change rate ΔQ ₀ are displayed for 1 second together with auxiliary display symbols (ST28, ST55, ST31,
ST53, ST52, ST32, ST54, ST35, ST33).
A state in which this Dj and the sedimentation change rate ΔQ ₀ are displayed on the display 8 is shown in FIG. 3b. In Fig. 3b, an auxiliary display symbol indicating that the particle diameter Dj and deposition change rate ΔQ ₀ are displayed is displayed, and the previously set particle diameter (e.g.
15μm) and the currently set particle size of 10μm, 23.1
% particle size distribution. After the deposition rate Q ₀ and the deposition change rate ΔQ ₀ are displayed together with the particle diameter for one second each, the elapsed time T and the deposition rate Q ₀ are displayed again every second. keyboard 9
When the call key provided _in The sedimentation rate Q ₁ at the time of pressing the key is subtracted to calculate the sedimentation change rate ΔQ ₀ and displayed in the same procedure as when the set particle diameter is reached (ST57). Note that the deposition rate Q ₀ when this call key is pressed is stored in the second deposition rate register, and is used as Q ₁ when the call key is pressed next. FIG. 3c shows a state in which the particle diameter Dj and the deposition rate _Q0 at that time are displayed by operating the call key. In Fig. 3c, there is an auxiliary display symbol indicating that the display was caused by pressing the call key, and the settled particle diameter at the time the call key was pressed was 28.3 μm, and particles larger than 28.3 μm were distributed at 52.3%. There is a sign indicating that it is. When the sedimentation progresses and the sedimentation rate _Q0 reaches a predetermined value, for example 90%, the contents of all flags and registers are cleared (ST18, ST58), and therefore from ST4 to ST5, ST6,
The average value W ₀ (sedimented weight) is displayed by ST7 and ST8, indicating that the measurement is complete.

In this way, the weight of the sample placed on the weighing pan in the air is converted to the weight in the medium, and the amount of the sample diffused in the sedimentation container and deposited on the sedimentation pan is divided by the above-mentioned weight of the sample in the medium. The deposition rate is calculated and displayed moment by moment along with the elapsed time. Further, the elapsed time is converted into a sedimentation particle size, and each time the value reaches a predetermined value, the particle size, sedimentation rate, and sedimentation change rate are held and displayed for a certain period of time. Furthermore, if the call key is pressed at any elapsed time, the settled particle diameter is calculated from the elapsed time at that point, and is held and displayed for a certain period of time together with the sedimentation rate and sedimentation change rate at that point.

As explained above, according to the present invention, the elapsed time and sedimentation rate are displayed immediately after the start of measurement and can be read directly, and there is no need to wait until all sedimentation is completed as in the conventional method. Furthermore, since the optimal display unit for elapsed time is selected depending on the sedimentation rate at the initial stage of sedimentation, there is no need to make any adjustments even if the samples have different sedimentation rates. Furthermore, each time the settled particle size calculated from the elapsed time reaches a preset value, the particle size, sedimentation rate, and rate of change in sedimentation are displayed for a certain period of time, allowing you to check the status of the particle size distribution of the sample. It is grasped sequentially during the measurement, and the conventional analysis work after the measurement is completed can be omitted. Furthermore, by operating the call key, it is possible to obtain the deposition rate for any elapsed time, that is, the particle size, which is particularly useful when obtaining information on the desired particle size and its distribution range.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention, FIGS. 2 a and b are flowcharts showing the processing program, and FIGS. 3 a, b, and c are respectively display states of the display device of the embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Load detection part, 2... Scale pan, 4... Sedimentation dish, 5... Control part, 6... Sedimentation container.

Claims (1)

[Scope of Claims] 1. A weighing pan, a settling dish suspended in a medium in a settling container, and the loads on the weighing dish and settling dish are detected, and are digitally converted and output at predetermined time intervals. a load detection unit; a means for converting the weight of the sample powder placed on the weighing pan into a sample weight in the medium using pre-input sample density and medium density; Means for calculating the weight of the sample deposited on the sedimentation dish by using the detected load when the sample powder on the weighing pan is diffused in the medium as a tare amount, and subjecting subsequent load detection values to tare subtraction processing. and means for calculating a sedimentation rate by dividing the sedimentation weight by the weight of the sample in the medium after the measurement start signal is issued, and displaying the sedimentation rate moment by moment along with the elapsed time from the generation of the measurement start signal. An electronic sedimentation balance equipped with means for 2 The above elapsed time T is calculated by the following formula to calculate the particle diameter.
Convert to Dj, and each time the particle size reaches a preset value, calculate by subtracting the particle size at that point, the sedimentation rate, and the sedimentation rate at the time when the immediately previous set particle size is reached from the sedimentation rate at that point. 2. The electronic sedimentation balance according to claim 1, wherein the electronic sedimentation balance is configured to hold and display the sedimentation change rate for a certain period of time. Dj=√18ηH/g(ρf−ρs)・T where η: Medium viscosity coefficient H: Distance from the medium liquid surface to settling plate g: Acceleration of gravity ρf: Sample density ρs: Medium density 3 Arbitrary Claims 1 or 2 are characterized in that, during the elapsed time, the particle diameter, sedimentation rate, and sedimentation change rate at that point in time are calculated by key operation, and are held and displayed for a certain period of time.
Electronic sedimentation balance as described in section. 4. Claims 1 and 2 are characterized in that the display unit of the elapsed time can be changed in accordance with the value of the sedimentation rate after a predetermined time has elapsed from the time when the measurement start signal is generated. or the electronic sedimentation balance described in paragraph 3. 5. Claims 1 and 2, characterized in that the measurement start signal is configured to be generated when the tare subtraction command key is set.
3. The electronic sedimentation balance according to item 1, 3 or 4.