JPH09178640A - Specific gravity measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the highly accurate specific gravity measurement without the requirement for a complicated circuit constitution for temperature measurement and the like and without the effects of the purity of liquid used by the simple constitution. SOLUTION: A sample 5 is mounted on a suspended tray 3, which is suspended from a balance 2, and a liquid-tank lifting and lowering mechanism 10 is moved up and down. Thus, the weight when the sample 5 is located in the air and the weight when the sample 5 is in liquid 7 are measured, and the specific gravity of the sample is computed. The density of the liquid 7 used in the computation can be accurately obtained by measuring the weight of a reference deadweight 8, whose mass and volume are known.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specific gravity measuring device for measuring the specific gravity of a solid sample or the like by measuring the weight in air and in a liquid of known density.

[0002]

2. Description of the Related Art In a conventional specific gravity measuring apparatus, a balance such as an electronic balance for measuring the weight of a sample by hanging the sample and a liquid tank filled with a liquid such as water having a known density under the balance. It has a mechanism for moving up and down, and is configured to be able to measure each weight when the sample is in the air and when it is submerged in the liquid by moving the liquid tank up and down. The buoyancy applied to the sample to be measured is measured by measuring the weight of the sample to be measured in air and the weight when the sample is submerged in the liquid by raising the liquid tank. The specific gravity of the sample is determined from the volume of the sample and the weight (mass) of the sample in the air.

This calculation requires that the density of the liquid be known. If the type of liquid is decided, its density can be known from the physical property table, etc., but since the density of liquid changes relatively greatly depending on its temperature, the temperature of the liquid is measured with a thermometer for precise specific gravity measurement. The liquid density value was corrected according to the temperature and used for calculating the specific gravity of the sample.

[0004]

As described above, in the conventional device, in order to determine the liquid density, the type of liquid and its temperature characteristics are stored in advance in the device, and the temperature of the liquid is measured at the time of actual measurement. The indirect method of measuring and calculating was used. However, this method not only complicates the circuit because it requires a sensor for temperature measurement and a temperature acquisition circuit, but also has the problem that the management of the liquid itself is troublesome because the purity of the liquid affects the measurement accuracy. Was there.

An object of the present invention is to provide a highly accurate specific gravity measuring device having a simple structure which does not require a complicated circuit structure such as temperature measurement, and which is not affected by the purity of the liquid used.

[0006]

In order to solve the above-mentioned problems, the present invention has a weighing scale and a liquid tank raising / lowering mechanism for moving a liquid tank filled with liquid up and down, and In a specific gravity measuring device for measuring the specific gravity of this sample from the weight and the weight in the liquid, a standard weight whose mass and volume are known is provided in the liquid tank, and the weight of the liquid of this standard weight is measured by measuring the weight of the liquid. The density was calibrated and this liquid density value was used to calculate the specific gravity of the sample.

Since the density of the liquid is calibrated in-situ using a reference weight whose mass and volume are known, the density of the liquid at that time can be accurately calculated even if the temperature of the liquid is different from the normal temperature, so that the sample The liquid temperature does not affect the calculation of the specific gravity of. Moreover, even if the purity of the liquid is slightly poor and the density is different from that of the pure liquid, the effect can be removed by the calibration with the reference weight.

When the temperature of the liquid is different from the normal temperature, the temperature of the reference weight contained in the liquid is also different from the normal temperature and some volume change occurs. Since the volume change is smaller than the volume change of liquid such as water, its influence can be ignored.

The specific gravity of an object is usually the same volume of 4 ° C.
The ratio of the weight of the object to the weight of pure water is the specific gravity in this specification, which is synonymous with the mass of the object per unit volume, that is, the density of the object.

[0010]

FIG. 1 shows an embodiment of a specific gravity measuring apparatus embodying the present invention. A balance 2 for measuring the weight is placed on an upper part of a gantry 1, and a hanging pan 3 for hanging a sample 5 is hung below the balance 2. As the balance 2, an electronic balance or the like is used, but any other type of balance such as a load cell type balance may be used as long as it can weigh.
Further, the hanging tray 3, which serves as the load, is hung from the bottom of the balance 2 in a suspended manner. A liquid tank raising / lowering mechanism 10 is installed at the bottom of the gantry 1, and a table 11 that moves up and down is provided.
A liquid tank 6 filled with a liquid 7 such as pure water is placed on the above.
As the upper and lower tables 11 of the liquid tank raising / lowering mechanism 10 move up and down, the liquid tank 6 moves up and down, and the sample 5 placed on the hanging tray 3 sinks into the liquid 7 or comes out of the liquid 7. Furthermore, a reference weight 8 for calibrating the density of the liquid 7 is placed in the liquid tank 6. A hook 9 is made upward from the reference weight 8 with a fine wire or the like, and the hook 9 is engaged with the bar 4 fixed to the hanging tray 3. The reference weight 8 also moves up and down according to the vertical movement of the liquid tank 6, and when the liquid tank 6 is upward, the hook 9 and the bar 4 are separated from each other, so that the load of the reference weight 8 is not applied to the balance 2 (Fig. 1 shows this state), and when the liquid tank 6 is lowered to the lowermost stage, the weight of the reference weight 8 is loaded on the balance 2 by the hook 9 being caught by the bar 4, and the liquid 7
The weight of the reference weight 8 inside will be measured.

FIG. 2 is a view for explaining how the relative positions of the sample 5, the liquid 7 and the reference weight 8 change depending on the vertical movement of the upper and lower tables 11. 2 (a) shows a state in which the tray 3 is not contained in the liquid 6 and the hook 9 of the reference weight 8 is not hooked on the bar 4 of the tray, and FIG. 2 (b) is a reference weight on the bar 4 of the tray. It costs 8 and the standard weight 8
Is separated from the bottom of the liquid tank and the weight in the liquid is measured. Further, in FIG. 2 (c), the pan 3 and the sample 5 placed thereon sink into the liquid and the weight of the sample in the liquid is measured. In this state, the hook 9 of the reference weight 8 is not hooked on the bar 4 of the hanging tray at this time.

The specific gravity is measured by the following procedure. First, Figure 2
Before placing the sample 7 on the pan 3 in the state of (a), the balance 2
Tare (setting the balance 2 to zero) is performed, and then the sample 7 to be measured is placed on the pan 3 and the sample 5
The weight W10 in the air of is calculated. Next, the liquid tank raising / lowering mechanism 10
2 is used to lower the liquid tank 6 mounted on the upper and lower tables 11 to obtain the value obtained by adding the weight W10 of the sample 5 to the weight W10 of the reference weight 8 in the liquid 7 to the state shown in FIG. 2B. . Next, the liquid tank 6 is raised, and the sample 5 is submerged in the liquid 7 as shown in FIG. 2C, and the weight W11 of the sample 5 in the liquid 7 is obtained. The specific gravity ρ of the sample 5 is calculated.

[0013]

(Equation 1)

[0014]

(Equation 2) The meaning of each symbol is as follows. ρ: specific gravity (density) of sample 5 W10: weight of sample 5 in air W11: weight of sample 5 in liquid 7 W20: weight of reference weight 8 in liquid 7 W3: weight of liquid 7 in lifting tray 3 D: Density of the liquid 7 W: Weight (mass) of the reference weight 8 V: Volume of the reference weight 8 contained in the liquid 7 S: Density of air

Here, the weight W of the reference weight 8, the volume V of the reference weight 8 and the density S of air are known values in advance, and the weight W3 of the liquid 7 in the tray 3 is also measured in advance. Keep it.

The calculation of the liquid density does not necessarily have to be performed every time, and may be performed only once at the start of measurement, or may be performed every fixed number of times of measurement. Alternatively, it may be performed only when a calibration command is given by the operator's judgment.

The liquid used is, for example, pure water, and its density is known to be about this value in a certain temperature range. Therefore, the result of calculating the liquid density by the above formula (2) is a predetermined value. If it is out of the range, it is judged that there is a high possibility that some kind of measurement error has occurred, and the fact is notified by blinking the indicator or turning on the dedicated display lamp.As a liquid density used for calculating the specific gravity. May use a specified value stored in advance.

Since the apparatus of the present invention can be used as an apparatus for measuring liquid density without adding special accessories, it is convenient to prepare a specific gravity measuring mode and a liquid density measuring mode as measuring modes. When the liquid density measurement mode is used, the liquid layer is filled with the liquid whose density is to be measured, and the hanging tray 3 is in a state of nothing.
As shown in (c), the liquid layer is lowered and the reference weight in this liquid 8
Is calculated, and the density of the liquid is calculated by the equation (2).

[0019]

Since the specific gravity measuring apparatus of the present invention calibrates the density of a liquid in-situ using a reference weight whose mass and volume are known, even if the temperature of the liquid is different from the normal one, the liquid at that time is calibrated. Since the density of is accurately calculated and the liquid temperature does not influence the calculation of the specific gravity of the sample, the specific gravity can always be measured with high accuracy regardless of the liquid temperature. Further, even if the purity of the liquid is somewhat poor and the density is different from that of the pure liquid, the effect can be removed by calibration with the reference weight, and the liquid can be easily prepared and managed. Further, the specific gravity measuring device of the present invention can be used as a liquid density measuring device without using a special accessory, and the range of use of the device is expanded.

[Brief description of the drawings]

FIG. 1 is an example of a specific gravity measuring apparatus embodying the present invention.

FIG. 2 is a diagram for explaining how the relative positions of a sample, a liquid, and a reference weight change depending on the vertical direction of a liquid tank.

[Explanation of symbols]

 1 ... Stand 2 ... Balance 3 ... Lifting pan 4 ... Bar 5 ... Sample 6 ... Liquid tank 7 ... Liquid 8 ... Standard weight 9 ... Hook 10 ... Liquid tank vertical mechanism 11 ... Vertical table

Claims (1)

[Claims] 1. A specific gravity measuring device having a weighing scale and an up-and-down mechanism for moving up and down a liquid tank filled with a liquid, and for measuring the specific gravity of the sample to be measured from the weight in air and the weight in liquid of the sample to be measured. In, a standard weight whose mass and volume are known is provided in a liquid tank, the density of the liquid is calibrated by measuring the weight of the standard weight in the liquid, and the specific gravity of the sample is calculated using this liquid density value. A specific gravity measuring device characterized by the above.