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Density Meter

Density meter used in laboratory

1. What is density meter?
    1.1 Working principle of density meter
    1.2 Application of density meter
2. Type of density meter
    2.1 Density measurement instrument
3. Use of density meter
    3.1 Precaution of density meter
4. How to buy density meter?

What is density meter?

Density meter is an instrument used to measure the density of an object. Laboratory densitometer is a type of instrument or device used in laboratories, laboratories, etc. to measure, analyze or study the density or concentration of a single specimen. It is characterized by high accuracy and requires careful operation and strict requirements for measurement conditions and environment.

The basic principle of density meter measurement is to measure the degree of darkening of the photographic material after exposure and development, i.e. blackness. In plate making, the silver bromide on the photographic material, subjected to the action of light, is reduced to metallic silver after the development, forming a certain degree of resistance to light. Blackness is large, high density; blackness is small, low density. A measuring meter with a filter can also measure the color density of color originals. The measurement principle is similar to the above basic principles.

There are two commonly used densitometers, one to measure the density of liquid density to pure water, called heavy table; the other to measure the density of the liquid in small water, called light table.

Working principle of density meter

The earth's gravity pulls the object toward the ground, but if the object is placed in a liquid, the buoyancy force will act on it in the opposite direction. The magnitude of the buoyancy force is equal to the gravity of the object draining the liquid.

Density meter is based on gravity and the balance of forces when an object is floating and Archimedes' principle. A fully functional densitometer can only be floating, so the force of buoyancy pushing upward is slightly greater than the force of gravity pulling downward. However, at equilibrium, the magnitude of the gravitational force on it is equal to the buoyancy force.

Because the gravity of the densitometer does not change, the volume of water discharged is the same. However, because it contains more water and becomes heavier. When the gravitational force is greater than the buoyant force, the densitometer will sink. The weight of the densitometer is less than the gravity of the same volume of water, so the densitometer refloats.

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 not uniform, sparse at the top, and dense at the bottom. When it is immersed in different liquids, the volume of the same sign changes, the densitometer bottom of the iron sand or lead particles is used to maintain the balance.

Measurement of fluid density of physical analysis instrument. Similarly, the specific gravity meter is an instrument for measuring the specific gravity of fluids. Density is the mass of a unit volume of material; specific gravity is the density ratio of a liquid or solid to water or gas to air at a specified temperature and pressure. The density of water and air at a certain temperature and pressure is known, therefore, the specific gravity and density under specified conditions are interchangeable. The density or specific gravity of a substance is related to the composition of the substance, so densitometers and specific gravity meters are commonly used to test the quality of, for example, alcohol, petroleum products, acid and alkaline solutions, gas, and natural gas. Densitometers can also be used for monitoring and controlling the production and processing of such products.

Density meter is mainly used to measure the concentration of hydrogen ions in liquids. To be precise, it measures the hydrogen ion activity and derives the value of acidity, neutrality, or alkalinity. Industrial liquid analyzers are widely used in tap water, river water, beverage, food, sewage, medical and chemical industries. The full range is 0-14pH, pH=7 is neutral, pH "7 is acidic, and pH close to 0 is strongly acidic. pH "7 is basic, and pH close to 14 is strongly basic.

Density meter uses the hydrogen ion activity of the liquid to be measured as the potential difference generated between the two electrodes and gets the transmission signal through the transmitter. The electrode that becomes the reference is called a glass electrode and is similar in appearance to a glass test tube. However, the front end is a thin film glass of tens of μmm made of special glass with an internal buffer and internal electrode built in. The internal electrode is essentially insulated from the liquid to be measured by a glass film. The electrode at the other end is called the comparison electrode (or reference electrode), and its structure is similar to that of the glass electrode, but there is a liquid junction at the front end, and the internal liquid is in contact with the liquid to be measured through a gap. The liquid junction has various forms, including glass fiber, small holes, ceramic, casing, etc., which are selected according to the specific purpose.

The impedance of the detection section is greater than 10MΩ due to the glass membrane separating them, so the transmission section needs a higher impedance, which must be 1GΩ or higher, and a highly insulated wire and terminal are also used between the amplifier and the electrode. The hydrogen ion activity of the measurement fluid causes a potential difference between the two sides of the film glass of the glass electrode. The potential on the inner side of the film glass of the glass electrode passes through the internal buffer and is exported through the inner electrode; while the potential on the outer side of the receiving liquid passes through the liquid to be measured - the reference electrode liquid interface - the internal liquid and is exported through the internal electrode of the reference electrode. The potentials generated between the internal electrode and the internal liquid of the two electrodes of the densitometer largely cancel each other out, so that the potentials on both sides of the glass of the film can be measured.

Application of density meter

A. Densitometer

Densitometers can determine the specific gravity of various fluids, semi-fluids, or mixtures. For example, cement slurry, sand slurry, mineral slurry, paper pulp, and random specific gravity in the process of chemical products and pharmaceutical products.

B. Concentrimeter

Concentrimeter can determine the percentage concentration (or proportion) of a solution or mixture. For example, the concentration of various solutions, mineral slurry, slurry, mortar, beverage flotation agent, etc. In conjunction with the flow meter, the instantaneous mass flow rate of dry minerals and the accumulated amount can be easily calculated.

Type of density meter

Density measurement instrument

A. Float densitometer

Float densitometer works on the principle that the buoyancy force on an object within a fluid is related to the density of the fluid, and the greater the density of the fluid, the greater the buoyancy force. If the temperature of the sample to be measured is specified (e.g., 25°C 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 specific gravity meter, abbreviated as glass specific gravity meter.

B. Hydrostatic density meter

Hydrostatic density meter works on the principle that the static pressure of a column of liquid at a certain height is proportional to the density of that liquid, so the density of the liquid can be measured according to the value of the static pressure measured by the pressure measuring instrument. A membrane box (see diaphragm and membrane box) is a commonly used pressure-measuring element, it directly measures the static pressure of the sample liquid column densitometer called the membrane box static pressure densitometer. Another commonly used is a single tube blowing densitometer. It measures air pressure instead of directly measuring the liquid column pressure. The blowing tube is inserted into the measured liquid surface below a certain depth, and compressed air through the blowing tube constantly escapes from the bottom of the tube. At this time, the pressure of the air inside the tube is equal to the pressure of the sample column at that height, and the pressure value can be converted to density.

C. Vibrating densitometer

Two famous Austrian scientists Hans Stabinger and Hans Leopard discovered the measuring principle of an oscillating tube densitometer. If a U-shaped glass tube is filled with a certain volume of liquid sample, the change of its vibration frequency or amplitude will reflect the mass or density and specific gravity of a certain volume of sample liquid. Two scientists later designed the prototype and handed it over to Mr. Urich Santner and his company Anton Paar to design the first digital liquid density meter in 1967. Fully automatic liquid densimeters are based on the principle of the U-shaped oscillating tube.

D. Radioisotope densitometer

The radioisotope densitometer is equipped with a radioisotope radiation source. Its radioactive radiation (e.g. γ-rays) is picked up by the radiation detector after passing through a certain thickness of the sample to be measured. The amount of radiation absorbed by a sample of a certain thickness is related to the density of that sample, and the signal of the ray detector is related to that absorption and therefore reflects the density of the sample.

Use of density meter

a. Clean the electrode with triple distilled water before using the densitometer, and pay attention to the glass electrode not to touch broken.

b. Prepare to put the NAOH liquid and HCL liquid next to the platform densitometer for adjustment.

c. Take out the fixed PH liquid (PH=7.0) in the refrigerator and put it on the platform.

d. Open the densitometer, adjust the PH value, press the ︿﹀ key to select PH and CAL options, select the CAL item, adjust the insertion into the PH liquid (PH = 7.0), press the " " key to select the data value to 7.0 at the appearance of a small eight fork can be.

e. Insert the glass electrode into the solution to be measured, then put in another electrode and stir the liquid surface appropriately (Note: do not touch the broken glass electrode).

f. When using the electronic unit of the densitometer the operator must pay attention to the protection of the circuit. When the PH value measurement is not carried out, the input of the densitometer should be short-circuited to avoid damage to the densitometer.

g. The glass electrode socket of the densitometer must be kept clean, clean and dry, and cannot be exposed to harmful gases such as salt spray and acid mist, while it is strictly forbidden to have any aqueous solution on the glass electrode socket to avoid high input impedance of the densitometer.

h. Be careful to add NaOH liquid or HCL liquid when the required PH value is not reached. (According to the different adjustment ranges, you can choose different concentrations of adjusting liquid; you can add it quickly when the concentration is small, and add it slowly when the concentration is large).

i. Be careful not to exceed the required constant volume when adding liquid.

Precaution of density meter

a. In general, the densitometer instrument in continuous use, is to be calibrated once a day; generally, within 24 hours the instrument does not need to be calibrated again.

b. Before use, pull down the rubber sleeve at the upper end of the densitometer electrode to expose the small hole at the upper end.

c. The buffer solution for calibration is generally pH=6.86 for the first time, and the buffer solution close to the pH of the measured solution is used for the second time.

d. When measuring, the introduction lead of the electrode should be kept static, otherwise it will cause unstable measurement.

e. Electrodes should never be immersed in distilled water. If the electrode used in the densitometer is new or has not been used for a long time, it must be soaked in distilled water for several hours before use, so that the asymmetric potential of the densitometer electrode can be reduced to a stable level, thus reducing the internal resistance of the electrode.

f. When the densitometer is used for PH measurement, it is important to ensure that the bulb of the electrode is completely inside the measured medium so that more accurate measurement results can be obtained.

How to buy density meter?

ANTITECK provide lab equipment, lab consumable, manufacturing equipment in life sciences sector.
If you are interested in our density meter or have any questions, please write an e-mail to, we will reply to you as soon as possible.

    AntiTeck Life Sciences Limited

    A1-519, XingGang GuoJi, Yingbin Road, Huadu, Guangzhou, China, 510810
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