First, let's take a brief look at the principle of using Cohen's balance to measure solid density:
1. The density of an object is its mass to volume ratio.
2. Density measurement is based on the Archimedes principle. This principle states that each solid immersed in a liquid loses the weight equal to the weight of the liquid it vents.
3. Solid density measurement usually uses a liquid of known density (eg water or ethanol) as an auxiliary liquid, which can be calculated by weighing the solids to be tested successively in air (A) and auxiliary liquid (B). Find its density.
Before making density measurements, Shangdao Han teaches you the following preparations:
1. Cohen balance. The accuracy of the electronic balance should be selected according to the specific requirements of the accuracy of the measured density data, and the capacity of the electronic balance should be selected according to the volume and weight of the sample to be tested. Before the test, it is necessary to preheat the prepared electronic balance for a long time and make necessary corrections to ensure the accuracy of the measurement data.
2. Test the components. It is necessary to select a suitable test component. For example, for some materials that are large in size and cannot be placed in the weighing chamber, the under-hook test component should be selected.
3. Sample to be tested. In order to measure the accuracy of the density in consideration of the influence of the surface tension of water, it is recommended that the weight of the sample to be measured be greater than 1 g. In order to improve the measurement accuracy, it is recommended to select a sample with a shape rule and a small surface roughness.
4. Select the appropriate auxiliary liquid. Generally chooseable: water, alcohol, and others. When testing the auxiliary liquid, it is necessary to select according to the nature of the specific test sample. For example, if it is easy to react with water, alcohol can be selected as the auxiliary auxiliary liquid.
Once you have the equipment and samples you need, follow these steps:
1. Open the left or right side of the electronic balance and remove the weighing pan and insert the density bracket into the electronic balance.
2. Place the bracket in the appropriate position above the bracket to ensure that the bracket does not come into contact with the bracket.
3. Place the beaker in the center of the stand. The Thermometer is inserted into the beaker to measure the current temperature of the liquid.
4. Inject a reference liquid of known density (usually water or alcohol) into the beaker to ensure that the solid to be tested can be fully immersed by the liquid more than 1 cm.
5. Place the hanging basket on the fixed bracket to ensure that there is no air bubble on the surface and does not touch the beaker or thermometer (see Figure 2 below).
6. Open the electronic balance switch 7. Close the windshield and remove the tare weight;
8. Open the electronic balance windshield and place the measured solid on the weighing arm of the fixed bracket or the weighing pan at the top of the hanging basket; if the mass of the measured solid in the air is greater than 20g, place it on the top of the hanging basket. Weighing in the weighing pan;
Note: For solids with a density less than the auxiliary liquid density, the weighing net at the bottom of the hanging basket should be reversed to press the object under test. If the buoyancy of the solid is greater than the weight of the hanging basket, the weighing must be assisted by placing an additional weight on top of the hanging basket. After loading the additional weight, the electronic balance is peeled and the weighing is started again. As shown in Figure 3 above.
9. Turn off the electronic balance windproof, after the electronic balance is stable, the electronic balance will automatically record the weighing result A (as shown in Figure 4 below);
10. Open the electronic balance windproof door, remove the solid to be tested, close the windproof door and remove the tare weight;
11. Open the electronic balance windproof door and place the measured solid in the weighing net at the bottom of the hanging basket, and ensure that no bubbles adhere to the solid surface (the surface bubbles can be removed with a small brush);
12. Close the electronic balance windproof door. After the electronic balance is stable, the electronic balance will automatically record the weighing result B. And calculate the density of the solid to be tested according to the density formula.
Note: For electronic balances such as Cohen AES and AEJ have been set up in the electronic balance software, the density data can be read directly, without manual calculation, and more healthy.
Electronic balances with density direct reading function: AEJ, industrial electronic balance, DE, FCE; electronic balance with density measurement function:
Improve the accuracy of the solid density measurement results 1. The surface tension of the auxiliary liquid The adhesion of the liquid to the hanging basket will increase the surface quality by 3 mg. When the hanging basket is immersed in the auxiliary liquid in the two weighings of the solid (in the air and the auxiliary liquid), the effect of the increase in the amount caused by the surface tension of the auxiliary liquid is negligible. Because the electronic balance is peeled off before each measurement. In order to reduce the effect of the bubbles and to ensure the possible accuracy of the large zoi, a few drops of wetting agent (not provided) can be used and added to the auxiliary liquid.
2. Temperature solids are generally not particularly sensitive to temperature changes, but when working with auxiliary liquids during density measurement, the greater influence of temperature on the liquid must be considered.
The change in density is generally caused on the order of 0.1 ° C to 1 ° C. This will affect the change in the third decimal place in the measurement result. It is recommended that the temperature of the auxiliary liquid be always taken into account during the solid density measurement.
1. The density of an object is its mass to volume ratio.
2. Density measurement is based on the Archimedes principle. This principle states that each solid immersed in a liquid loses the weight equal to the weight of the liquid it vents.
3. Solid density measurement usually uses a liquid of known density (eg water or ethanol) as an auxiliary liquid, which can be calculated by weighing the solids to be tested successively in air (A) and auxiliary liquid (B). Find its density.
Before making density measurements, Shangdao Han teaches you the following preparations:
1. Cohen balance. The accuracy of the electronic balance should be selected according to the specific requirements of the accuracy of the measured density data, and the capacity of the electronic balance should be selected according to the volume and weight of the sample to be tested. Before the test, it is necessary to preheat the prepared electronic balance for a long time and make necessary corrections to ensure the accuracy of the measurement data.
2. Test the components. It is necessary to select a suitable test component. For example, for some materials that are large in size and cannot be placed in the weighing chamber, the under-hook test component should be selected.
3. Sample to be tested. In order to measure the accuracy of the density in consideration of the influence of the surface tension of water, it is recommended that the weight of the sample to be measured be greater than 1 g. In order to improve the measurement accuracy, it is recommended to select a sample with a shape rule and a small surface roughness.
4. Select the appropriate auxiliary liquid. Generally chooseable: water, alcohol, and others. When testing the auxiliary liquid, it is necessary to select according to the nature of the specific test sample. For example, if it is easy to react with water, alcohol can be selected as the auxiliary auxiliary liquid.
Once you have the equipment and samples you need, follow these steps:
1. Open the left or right side of the electronic balance and remove the weighing pan and insert the density bracket into the electronic balance.
2. Place the bracket in the appropriate position above the bracket to ensure that the bracket does not come into contact with the bracket.
3. Place the beaker in the center of the stand. The Thermometer is inserted into the beaker to measure the current temperature of the liquid.
4. Inject a reference liquid of known density (usually water or alcohol) into the beaker to ensure that the solid to be tested can be fully immersed by the liquid more than 1 cm.
5. Place the hanging basket on the fixed bracket to ensure that there is no air bubble on the surface and does not touch the beaker or thermometer (see Figure 2 below).
6. Open the electronic balance switch 7. Close the windshield and remove the tare weight;
8. Open the electronic balance windshield and place the measured solid on the weighing arm of the fixed bracket or the weighing pan at the top of the hanging basket; if the mass of the measured solid in the air is greater than 20g, place it on the top of the hanging basket. Weighing in the weighing pan;
Note: For solids with a density less than the auxiliary liquid density, the weighing net at the bottom of the hanging basket should be reversed to press the object under test. If the buoyancy of the solid is greater than the weight of the hanging basket, the weighing must be assisted by placing an additional weight on top of the hanging basket. After loading the additional weight, the electronic balance is peeled and the weighing is started again. As shown in Figure 3 above.
9. Turn off the electronic balance windproof, after the electronic balance is stable, the electronic balance will automatically record the weighing result A (as shown in Figure 4 below);
10. Open the electronic balance windproof door, remove the solid to be tested, close the windproof door and remove the tare weight;
11. Open the electronic balance windproof door and place the measured solid in the weighing net at the bottom of the hanging basket, and ensure that no bubbles adhere to the solid surface (the surface bubbles can be removed with a small brush);
12. Close the electronic balance windproof door. After the electronic balance is stable, the electronic balance will automatically record the weighing result B. And calculate the density of the solid to be tested according to the density formula.
Note: For electronic balances such as Cohen AES and AEJ have been set up in the electronic balance software, the density data can be read directly, without manual calculation, and more healthy.
Electronic balances with density direct reading function: AEJ, industrial electronic balance, DE, FCE; electronic balance with density measurement function:
Improve the accuracy of the solid density measurement results 1. The surface tension of the auxiliary liquid The adhesion of the liquid to the hanging basket will increase the surface quality by 3 mg. When the hanging basket is immersed in the auxiliary liquid in the two weighings of the solid (in the air and the auxiliary liquid), the effect of the increase in the amount caused by the surface tension of the auxiliary liquid is negligible. Because the electronic balance is peeled off before each measurement. In order to reduce the effect of the bubbles and to ensure the possible accuracy of the large zoi, a few drops of wetting agent (not provided) can be used and added to the auxiliary liquid.
2. Temperature solids are generally not particularly sensitive to temperature changes, but when working with auxiliary liquids during density measurement, the greater influence of temperature on the liquid must be considered.
The change in density is generally caused on the order of 0.1 ° C to 1 ° C. This will affect the change in the third decimal place in the measurement result. It is recommended that the temperature of the auxiliary liquid be always taken into account during the solid density measurement.
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