What instrument to use to measure density How does a density meter measure density

I use the most principled measurement method.

Prepare an electronic scale.

Prepare a bucket of water.

Place the measured object in the water and find the volume.

The weight of the object to be measured is electronically weighed.

Density = weight volume.

1. Definition of densityDensity refers to the weight of a substance per unit volume.

D w v is also known as d wa (wa ww), which is usually represented by g cm3.

wa: The weight of the sample in air.

ww: The weight of the sample in water.

2. Determination of density1. Simple geometric shapes:

Solid cylinder.

bc = d/vc = d/(pr2h)

Rectangular rods or flat plates.

br = d/vr = d/(lwh)

BC, BR and VC, VR are the overall density and volume, respectively.

d: is the weight of the body being tested r: is the radius, h: is the height l: is the length, w: is the width p =.

2. Objects with complex shapes:

w: weight of the sample in air ww: weight of the sample in water.

However, the bulk density required for porous products is tested with three variables, wa (wb-ww). Also known as bulk density.

wa: The weight of the sample in air.

wb: The weight of the sample in air after waterproofing.

ww: The weight of the sample in water after waterproofing.

Nowadays, most of them use electronic density meters to measure density, and Dahong Meituo electronic density meter is a new type of density testing instrument developed by combining modern microelectronic technology with Archimedes' principle.

First of all. Estimate the possible range of the measured liquid density values and select the density meter according to the required accuracy

Secondly. Carefully clean the density meter When measuring the density of liquid, hold the part above the highest engraved line of the dry pipe with your hand and pick it up vertically

And then. After the container is cleaned, slowly pour in the liquid to be measured, and stir continuously so that there are no bubbles in the liquid, and then put it into the density meter The liquid part of the density meter should not be attached to the liquid part

And then. The density meter should be washed and cleaned before use After the density meter is immersed in liquid, if the meniscus surface is abnormal, the density meter should be washed again

At last. When reading, the lower part of the meniscus is subject to the inscription As shown in the figure When reading, the density meter should not be in contact with the wall, bottom of the container and the agitator For opaque liquids, only the upper edge of the meniscus can be read.

The density measurement method is as follows:

1. Weighing method. Equipment: balances, graduated cylinders, water, metal blocks, strings.

Steps: Weigh 1 and weigh the mass of the metal block with a balance; Scale 2 and inject an appropriate amount of water into the graduated cylinder, and the reading volume is v1; Weigh 3 with a thin string to tie the metal block into a graduated cylinder, immersion, and read the volume of v2. Called the calculation expression:

m/(v2-v1)。

2. Weigh the proportional cup method. Weighing equipment: beaker, water, metal block, balance.

Steps: Weigh 1 and fill the beaker with water, put it on the balance and weigh the mass as m1; Weigh 2, gently put the subordinate block into the water, overflow part of the water, and then put the beaker on the balance to weigh the mass as m2; Weigh 3 Take out the metal block, place the beaker on the balance and weigh out the mass of the beaker and the remaining water m3. Called the calculation expression:

Water. >3. Called Archimedes' Law. Weighing equipment: spring scales, metal blocks, water, strings.

Steps: Weigh 1 to tie the metal block with a string, and weigh the gravity g of the metal block with a spring scale; Weigh 2 completely immerse the metal block in water, and weigh the apparent weight g of the metal block in the water with a spring scale; Called the calculation expression: =g water (g-g).

4. Weigh the buoyancy method (1). Weighing equipment: wooden blocks, water, fine needles, graduated cylinders.

Steps: Weigh 1 and inject an appropriate amount of water into the graduated cylinder, and the reading volume is V1; Weigh 2 put the wooden block into the water, float, and read the volume v2 after being stationary; Scale 3 is inserted into the wooden block with a fine needle, the wooden block is completely immersed in water, and the reading volume is v3. Water.

5. Weighing buoyancy method (2): equipment: scale, cylinder cup, water, small plastic cup, small stone.

Steps: Weigh 1 Put an appropriate amount of water in the cylinder cup, then gently put the mouth of the plastic cup upward, let it float, and measure the height of the water in the cup h1 with a scale; Weigh 2, gently put the small stone into the cup, float, and measure the height of the water h2 with a scale; Take the small stone out of the cup, put it in the water, sink it, and measure the height of the water h3 with a scale. Evaluate Expressions:

Water (H2-H1) (H3-H1).

6. Density meter method: equipment: eggs, density meter, water, salt, glass.

Steps: Weigh 1 Pour an appropriate amount of water into the glass, gently put the eggs in, and sink the eggs; Weigh 2 and gradually add salt to the water, stir with a density meter while adding until the egg floats, and measure the density of the brine with a density meter, that is, wait for the density of the egg.

Density = mass volume, e.g. density of water = 1 ton cubic meter.

The mass is reversed, the volume is more, and different shapes are calculated differently. The simplest length*width*height = cube volume.

The law of change in density.

Generally speaking, no matter what substance it is in, no matter what state it is in, with the change of temperature and pressure, the volume or density will also change accordingly. The relationship between the three physical quantities of temperature t, pressure p, and density (or volume) is called the equation of state. The volume of a gas varies significantly depending on the pressure it is subjected to and the temperature it is subjected to.

For an ideal gas, the equation of state is where r is the gas constant, equal to m2 (sec2*keon). If its temperature does not change, the density is proportional to the pressure; If its pressure is constant, the density is inversely proportional to the temperature. For general gases, if the density is not large and the temperature is far away from the liquefaction point, its volume changes with pressure and is close to the ideal gas; For gases with high density, the above equation of state should also be appropriately modified.

The density of a solid or liquid substance changes only slightly when temperature and pressure change. For example, around 0, the temperature coefficient (the rate of change in the volume of an object when the temperature increases by 1) is mostly around 10-9 for various metals. The pressure in deep water and the pressure under water** can reach several hundred atmospheres, or even higher (1 atmosphere = 101325 Pa), and the change in density with pressure must be taken into account.

Cole recommends the following equation of state:

where p0 is the density of water at atmospheric pressure. If n and b are taken as 7 and 3000 atmospheres, then up to 105 atmospheres, the errors of the above equations and measured data are within a few percent.

In nature as a whole, extreme pressures can cause the density of matter in some celestial bodies to vary greatly from the usual density, such as neutron stars, which can reach a density of 10 grams3.

Determination of density steps:

1. Measure the mass of the object.

2. Measure the volume of the object.

3. Divide the mass of the object by its volume.

The density of an object is determined by its mass per unit volume. In geology, metallurgy and other physical sciences, density is one of the characteristic properties of rocks, minerals and metals. Density is also used to calculate whether an object can float in a known liquid.

1. Measure the mass of the object. The mass of an object, in simple terms, is how much it contains. You can weigh the object with a scale or a spring scale to know its mass.

If the object is weighed in a container, such as a liquid or powder in a graduated cylinder, then the mass of the container must be measured when it is empty, so that the mass of the object in the container is its total mass minus the mass of the container.

2. Measure the volume of the object. The volume of an object is the space it occupies. Different object volumes can be measured by different methods depending on the characteristics of the object:

If the object is a solid with a regular shape, measure its length, width, and height (or the length and diameter of a cylinder), and we can calculate the volume from its shape. Different shapes of objects such as boxes, cylinders, and cones have different formulas for calculating volume.

3. Divide the mass of the object by its volume. This value is the density of the object, which is measured in mass per unit volume. For example, for an object with a volume of 20 cm with a mass of 5 g, its density is 4 g cm.

A density meter is an instrument that measures the density of a liquid.

The density meter is a glass tube with a special shape marked with a scale on the upper part, and a small lead pellet is encapsulated in the glass bubble at the bottom of the tube, and when it is placed in the liquid, the density of the liquid can be directly read according to the depth of the density meter immersed in the liquid.

The density meter is made according to the balance of gravity and the force of the object when floating and the Archimedes' principle. A functioning density meter can only be floating, so the buoyancy pushes upwards slightly more than the gravity pulls downward. But in equilibrium, the gravitational force is equal to the buoyant force.

Because the gravity of the density meter does not change, the volume of water it discharges is the same. However, it becomes heavier because it contains more water than it contains. When gravity is greater than buoyancy, the density meter sinks.

The weight of the density meter is less than the gravity of the same volume of water, so the density meter floats again. The reading of the density meter is large at the bottom and small at the top, and the scale value from top to bottom is gradually increasing, but the scale is uneven, and the top is sparse and the bottom is dense.

Types of density meters

1. Float density meter.

The working principle is that the buoyancy experienced by an object in a fluid body is related to the density of the fluid, and the greater the density of the fluid, the greater the buoyancy. If the temperature of the sample to be measured is specified, the instrument can also use the specific gravity value as a scale value. The simplest of these instruments is the visual float type glass hydrometer, referred to as the glass hydrometer.

2. Hydrostatic density meter.

The working principle is that the static pressure of a liquid column at a certain height is directly proportional to the density of the liquid, so the density of the liquid can be measured according to the static pressure value measured by the pressure measuring instrument. The diaphragm cassette is a commonly used pressure measuring cell, and the density meter that directly measures the static pressure of the sample liquid column is called a diaphragm hydrostatic density meter.

Another commonly used type is a single-tube blow-off density meter. It measures air pressure instead of directly measuring liquid column pressure. The blowing tube is inserted to a certain depth below the liquid level of the liquid to be measured, and the compressed air continuously escapes from the bottom of the tube through the blowing tube.

In this case, the pressure of the air in the tube is equal to the pressure of the sample column at that height, and the pressure value can be converted into density.

The method of measuring the degree of the secret car is as follows:1. Weighing method:

Equipment: balances, graduated cylinders, water, metal blocks, strings.

Steps: 1. Use the balance to weigh the mass of the metal block;

2. Inject an appropriate amount of water into the graduated cylinder, and the reading volume is V1;

3. Tie the metal change block with a string and put it into a graduated cylinder, immerse it, and read the volume as V2;

Evaluate expression: =m (v2-v1).

Second, the gravity cup method:

Equipment: beaker, water, metal block, balance.

Steps: 1. Fill the beaker with water and put it on the balance to weigh the mass as m1;

2. Gently put the subordinate block into the water, overflow part of the water, and then put the beaker on the balance to weigh the mass as m2;

3. Take out the metal block, put the beaker on the balance and weigh the mass m3 of the beaker and the remaining water;

Calculation expression: = water (m2-m3) (m1-m3).

3. Archimedes' Law:

Equipment: spring scales, metal blocks, water, strings.

Steps: 1. Tie the metal block with a string, and weigh the gravity g of the metal block with a spring scale;

2. Completely immerse the metal block in water, and weigh the apparent weight g of the metal block in the water with a spring scale;

Calculation expression: =g water (g-g).

Fourth, the density meter method:

Equipment: eggs, density meter, water, salt, glass.

Steps: 1. Pour an appropriate amount of water into the glass, gently put the egg into the closed dig, and the egg sinks;

2. Gradually add salt to the water, stir with a density meter while adding until the egg floats, and measure the salt water with a density meter;

The density is equal to the density of the egg.