JPS5910604Y2 - Particle size distribution measuring device - Google Patents

Description

[Detailed description of the invention] This invention relates to an improvement of an apparatus for measuring the particle size distribution of powder by a sedimentation method in which particles naturally settle in a medium, and the measurement principle is well known (from Stokes' equation). V: Sedimentation velocity cm/sec ρS: Density of medium g/image H: Sedimentation distance crn ρf: Density of powder g/rm T: Sedimentation time sec η: Viscosity coefficient of medium g/cm.SeC g: Gravity There is a relationship where the acceleration cm/sec2 r is the radius of the particle cm, and from this equation, K is a constant determined by time T.

Therefore, the T of the liquid in which particles of various diameters were initially uniformly suspended
Looking at the state after time, at depth H from the liquid surface, r=
There are no particles with a diameter larger than Ki, and on the other hand, the density of each particle size in the suspension is constant regardless of time, so the difference between the specific gravity of the suspension at depth H and the specific gravity of only the medium is W is defined as W=/rw (r) dr, r=Kv'n ・・−, where w (r) is the specific gravity distribution of particles of each particle size in the medium.
...(.3).

Since W is a function of r and r is a function of H, W is a function of H, and if we characterize the relationship curve between W and H, we can find w(r), that is, the weight distribution of each particle size of the powder. It will be done.

Now, if we record W as a function of H, then dW/d
In order to obtain r=w(r), it is convenient to convert H to r from the beginning.

The procedure for recording the relationship between W and H (i.e., r) based on this principle is as shown in measurement section A in Figure 1, by suspending sinkers 6 at both ends of the balance 1 and suspending the sample powder for a certain period of time. The table 4 on which the sedimentation bottle 2 containing the aged suspension and the sedimentation bottle 3 containing only the medium are placed under both arms of the balance is moved at a relatively high speed (by the equation (2) above) using the motor 5. The sinking weight 6 is lowered into both liquids by raising T at a constant value (that is, within a time period that allows K to be considered constant), and the light source lamp 8 is used to correct the deflection of the pointer 7, that is, the unbalance caused by the density difference between the two liquids. This is detected by the photoelectric detector 9, and is amplified by the density difference measuring amplifier F. The output thereof controls the magnet 10 so that the pointer 7 points to the O position, and the current necessary for this control controls the suspension. The density of the powder inside is determined, and the amount of rise of the platform 4 (the amount of descent of the sinking weight from the liquid level) is taken as H on the horizontal axis, and the density obtained above is taken as the vertical axis, and W in the above formula (3) is calculated. Record it on the chart.

Figure 2 shows the records obtained in this way, T=O, Tl
, T2, ... shows the case of infinity.

Since H on the horizontal axis can be converted to the particle size r using the previous equation (3), it is convenient to convert the horizontal axis to r from the beginning.

Furthermore, since the particle size distribution width L is wider, the horizontal axis is usually set to logr in order to fit this into a practical chart length.

However, conventionally, the above-mentioned drop H from the liquid level is proportionally converted into an electric signal, and the signal proportional to H is directly logarithmically converted to logr=1ogK++ (1ogH)/2, which is calculated as logr=1ogK++ (1ogH)/2. I was getting numbers.

The amount directly obtained in this apparatus is H, and r
= KJFF, so in the region where r is small, the difference in r due to a slight change in H is large, and therefore the influence of the error in H is large.
If logr is calculated as (logH)/2, the error will be large where r is small.

In addition, the sinking weight has a size, and the density difference between the sample suspension and the medium starts from the height h when the sinking weight is completely submerged under the liquid surface, and the measurement does not start from H-0. Therefore, the following correction is necessary, but in the past, this correction was not performed manually.

One purpose of the present invention is to reduce the above error in a region where r is small.

Furthermore, H in the above equation (3) is the amount of descent of the sinker 6, but since the sinker 6 must be completely immersed in the liquid in order to actually measure the density, the density below the water surface cannot be measured from H=O. na<hc
m (usually about 1 cm), and for this reason, the actual travel distance H' to raise the platform 4 on which the sedimentation bottle is placed is not the theoretical H, but the relationship H = H' + h. ing.

The present invention attempts to simplify the device by performing the calculation of H'+h in the H→logr conversion means using a special addition device.

In order to achieve the above objectives, the present invention includes a balance that converts the buoyancy difference between the sample suspension and the sinker in the medium into an electrical signal, and a balance that outputs a voltage proportional to the route of the displacement of the slider. comprising a potentiometer having a resistance distribution, and a mechanism for integrally moving up and down a sedimentation tank containing a sample suspension and a medium tank, and interlocking the slider of the potentiometer with the up and down movement of the sedimentation tank, Connect the slider of the potentiometer to a logarithmic conversion circuit, connect the output terminal of this logarithmic conversion circuit to the X-axis signal terminal of the recorder,
The electric signal output terminal of the balance is connected to the Y-axis signal terminal of the recorder, and a voltage correction value corresponding to the depth at which the density difference measurement between the sample suspension and the medium is started is connected in series with the resistance of the potentiometer. The present invention provides a particle size distribution measuring device characterized in that a series resistance portion is added to give the following characteristics.

With the above structure, the amount of vertical movement of the settling tank and the medium tank is converted by the potentiometer into a signal proportional to the square root thereof, and the signal proportional to the square root of this vertical movement is logarithmically converted. Compared to directly logarithmically converting the amount of movement, changes in r are less sensitive to changes in the amount of vertical movement in a region where r is small. By connecting , the fact that the measurement cannot be started from H=0 can be corrected dynamically.

FIG. 1 shows an embodiment of the present invention.

As mentioned above, A is the measuring section, and sinking weights 6 are suspended from both arms of the balance 1, and are immersed in the liquid in the sedimentation bottles 2 and 3 placed on the table 4.

The liquid levels in the bottles 2 and 3 are made to be at the same height, and the stand 4 is moved up and down by a motor 5.

C is a vertical mechanism control unit that rotates the motor 5 in the normal direction to raise the platform 4 at a constant speed to a predetermined height, and then rotates the motor in the reverse direction to lower it to the original position.

Since bottle 2 contains the sample suspension and bottle 3 contains only the medium, the difference in weight of sinker 6 immersed in the liquid in each bottle is the same as that between both bottles. This corresponds to the difference in the density of the liquid at the depth at which the sinker 6 is immersed in the sample liquid, and this density difference corresponds to the difference in the density of the liquid contained in the same volume as the sinker at that depth in the sample liquid. is the weight W of the particles (formula (3) above).

The output of the density difference measuring amplifier F is the weight W converted into an electrical signal.

The rising speed of the platform 4 is sufficiently faster than the sedimentation speed of the particles in the sample liquid in the bottles 2, and until the sinking weight 6 reaches the bottom from the surface of the liquid in the bottles 2 and 3, the particles in the sample liquid are The distribution of particle diameters in the depth direction can be considered to be unchanging, and the above-mentioned K may be kept constant during that time.

R is a root function generating circuit, which is a potentiometer P as shown in FIG. 3, and its slider S is connected to a platform 4, and as the platform 4 moves up and down, the slider S slides on the resistance of the potentiometer P.

The vertical movement distance of the slider S matches the vertical movement distance of the table 4, and the slider S is located at the lower end of the potentiometer P in FIG. 3 when the table 4 is at its lowest position.

The lifting distance of the platform 4 from this position is the above-mentioned H'.

At the lowest position of the platform 4, the sinking weight 6 is completely immersed in the liquid in the bottles 2 and 3, and is at a height h below the liquid surface (
Pour the liquid into bottles 2 and 3 like that).

Therefore, the root function generating circuit R needs to output a signal proportional to v'n-1.

For this purpose, a resistor P is connected in series to the lower end of the potentiometer P.

The potentiometer P, including this resistance P', has a winding pitch of the sliding resistance wire at the bottom so that a voltage proportional to JH'+h is obtained on the slider S at the position where the slider S is raised by H from the bottom end of P. The pitch becomes coarser as it goes up.

With this structure, the root function generating circuit R outputs a voltage signal proportional to JH'+h at a position where the sinking weight 6 is submerged by H'+h from the liquid surface.

This voltage signal is applied to the logarithmic conversion circuit L, and a signal below log -, IFF = log v' is obtained from the circuit L.

Density difference measurement amplifier F while raising platform 4 from the lowest position.
When the output signal of is applied as a Y-axis signal to the recording section D using an XY recorder, and the output of the logarithmic conversion circuit L is applied as an X-axis signal, the horizontal axis is set to 10 gJ\I, and the vertical axis is set to W. A chart as shown in FIG. 2 is obtained.

A chart like this is shown at T1 after injecting the sample solution into bottle 2.
Take the sample after an appropriate time, such as after T2 hours.

The horizontal axis of the chart mentioned above is log! ' and its starting end (left end) starts from logJK.

Therefore, to find the particle diameter r from the reading on the scale of this horizontal axis, use the time T when the chart was taken (the elapsed time from when the sample liquid was injected into the bottle 2) to calculate the K calculated using the formula (2) above. After calculating logK from the value and adding it to the scale reading on the horizontal axis, the antilog of that number is calculated (antilogarithmic transformation).

When using paper with a logarithmic scale on the horizontal axis for the chart, the particle size can be immediately determined by multiplying the reading on the horizontal scale by K.

This method can also be applied to a type of particle size measuring device that detects concentration changes using a light transmission method while moving a sedimentation bottle upward.

As mentioned above, the present invention uses a potentiometer that converts the amount of descent of the sinking weight to convert the amount of descent of the sinking weight into an electrical signal to compensate for the fact that density measurement using a sinking weight cannot be performed from the liquid level, so no separate correction means is required. The device is simple, and the potentiometer is used not only for displacement voltage conversion but also for root conversion, and when converting the sinking weight drop into the logarithm of the particle size, root conversion is performed instead of direct logarithmic conversion. By inserting , the error due to the sensitivity of the change in r to the change in H in the small diameter region due to the relationship r=KV perspiration can be removed without adding any other means.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the device of the present invention, FIG. 2 is an example of a chart obtained by sedimentation method particle size measurement, and FIG. 3 is a circuit diagram of the root function generating circuit of the device of the present invention. DESCRIPTION OF SYMBOLS 1... Balance, 2... Sedimentation bottle for suspension, 3... Sedimentation bottle for medium, 4... Stand, 5... Motor, 6... Sinking weight, 7... Pointer, 8... Light source lamp, 9... Light source detector, 10... Magnet.

Claims (1)

[Scope of utility model registration request] A balance that converts the buoyancy difference between the sample suspension and the sinking weight in the medium into an electrical signal, a potentiometer that has a resistance distribution that outputs a voltage proportional to the route of the displacement of the slider, and the sample suspension. The slider of the potentiometer is linked with the vertical movement of the sedimentation tank, etc., and the slider of the potentiometer is connected to a logarithmic conversion circuit. and connect the output terminal of this logarithmic conversion circuit to the X of the recorder.
Connect the electric signal output terminal of the balance to the Y-axis signal terminal of the recorder, and start measuring the density difference between the sample suspension and the medium in series with the resistance of the potentiometer. A particle size distribution measuring instrument characterized by adding a series resistance part that gives a voltage correction value corresponding to the depth of the particle size distribution.