KERN & Sohn GmbH Ziegelei 1 D-72336 Balingen email: info@kern-sohn.com Phone: +49-[0]7433- 9933-0 Fax: +49-[0]7433-9933-149 Internet: www.kern-sohn.com Operating instructions Density Determination Set for Analytical Balance KERN ABJ / ABS KERN ABS-A02 Version 1.
KERN ABS-A02 GB Version 1.0 04/2010 Operating instructions Density Determination Set for Analytical Balance KERN ABJ / ABS Contents: 1 INTRODUCTION ............................................................................................................................ 3 1.1 2 SCOPE OF SUPPLY .................................................................................................................... 3 PRINCIPLE OF DENSITY DETERMINATION........................................................
1 Introduction • In order to guarantee a safe and trouble-free operation, please read carefully the operating instructions. • These operating instructions only describe the operation of the density determination set. For further information on how to operate your balance please refer to the operating instructions supplied with each balance. 1.1 Scope of supply Ö Check packaging and density determination set immediately when unpacking for possible visible damage.
Fig. 2: Installed density set KERN ABS-A02 Fig. 3: Combination weighing trays A Upper sample dish (weight of the sample in air) B Lower sample dish (weight of the sample in measuring liquid) Fig.
2 Principle of Density Determination Three physical magnitudes are the volume and the mass of bodies as well as the density of matter. In density mass and volume are related. Density [ ρ ] is the relation of mass [ m ] to volume [ V ]. ρ= m V SI-unit of density is kilogram divided by cubic meter (kg/m³). 1 kg/m³ equals the density of a homogenous body that, for a mass of 1 kg, has the volume of 1 m³.
Determining density of liquids The density of a fluid is determined with the help of a sinker providing a known volume [ V ]. The sinker is weighed in air [ A ] as well as in the sample fluid [ B ]. According to the Archimedes’ Principle a body immersed in a fluid experiences a force of buoyancy. [ G ]. This force equals the weight force of the fluid displaced by the volume of the body. The volume [ V ] of the immersed body equals the volume of the displaced fluid.
3 Installing the density determination set • If necessary, carry out necessary adjustment before installation of the density set. • When the density set is installed, correct adjustment is not possible. • For reasons of adjustment, take away the density set and place the standard weighing plate. 1. Switch off balance and separate it from the power supply. 2. Remove standard weighing plate, screening ring and weighing plate carrier. 3. Insert balance tray holder carefully 4.
6. Close the glass doors. Connect balance to power supply, the balance will carry out a self-test. The balances of the ABJ series also carry out an adjustment with the internal adjustment weight. Wait until “off“ appears. 7. Press the ON/OFF key, the gram display will appear. 8. Fix the thermometer according to the illustration on the glass container. Fill the glass container with measuring or sample liquid. 9.
4 Density determination of solids for the density determination of solid material, the solid is weighed first in air and then in the measuring liquid. From the weight difference results the buoyancy from where the software calculates the density. 4.1 Activate function In the „Unit.SEL“ menu the density determination function for solid material „U- Td“ can be activated, which then will be available for the operator without needing to enter the menu each time.
4.2 Input „Density measuring liquid“ Ö In the gram display press the CAL/MENU button repeatedly until „SettinG“ appears. Ö Press the TARE/ button. Ö Press the CAL/MENU button repeatedly until “LSG SEt“ appears (Example) (Example) Ö Press the TARE/ button, the currently set density is displayed. In the upper part of the display panel, the symbol and the # symbol appear in order to indicate numerical input status. The first digit is flashing and can be changed.
4.3 Measurement „Density solid material“ 1. Repeatedly press the UNIT/ button until the balance is in density determination mode for solid material „Td". If the weight is measured in air, additionally a „g“ will be displayed. 2. Press the TARE/ dish. button. Place sample in the upper sample 3. When standstill control is complete, press the CAL/MENU button. 4. Place sample in the lower sifting bowl. When standstill control is complete, the density of the sample will be shown in the display.
5 Determining density of liquids For density determination of liquids, a glass sinker is used, whose volume is known. The glass sinker is weighed first in air and then in the liquid whose density is to be determined. From the weight difference results the buoyancy from where the software calculates the density. 5.1 Activate function In the “Unit.
5.2 Determine volume of the glass sinker If the volume of the glass sinker is unknown, it must be determined and calculated as follows. Ö Fill water into the container and heat it until the temperature is constant. Read temperature on the thermometer. Ö If necessary, press the UNIT/ button until the gram display appears. Ö Remove the combination weighing tray if necessary. May be that „ol“ will be displayed, but in that step this isn’t any error message and can be ignored.
5.3 Enter volume of the glass sinker Ö In the gram display press the CAL/MENU button repeatedly until „SettinG“ appears. Ö Press the TARE/ button. Ö Press the CAL/MENU button repeatedly until „Sv SEt“ appears (Example) (Example) Ö Press the TARE/ button, the currently set volume is displayed. In the upper part of the display panel, the symbol and the # symbol appear in order to indicate numerical input status. The first digit is flashing and can be changed.
5.4 Measurement „Density liquid“ 1. Suspend the glass sinker. If no glass sinker is suspended, may be „oL“ will be displayed, however in this step it is no error message and can be ignored. 2. Repeatedly press the UNIT/ button until the balance is in density determination mode for liquids "d". If the weight is measured in air, additionally a „g“ will be displayed. 3. Press the TARE/ button. 4. When standstill control is complete, press the CAL/MENU button 5. Remove the glass sinker. 6.
6 Preconditions for Precise Measurements There are numerous error possibilities during density determination. Accurate knowledge and caution are required to achieve precise results when applying this density set in combination with the balance. 6.1 Calculation of Results The balance displays results for density determination by giving four decimal places. However, this does not mean that the results are accurate down to the last decimal place as this would be the case for a calculated value.
6.2 Influence Factors for Measurement Errors 6.2.1 Air bubbles A small bubble of, for example, 1mm3 will have a considerable influence on the measurement if the sample is small. Buoyancy will be increased by approximately 1mg resulting immediately in an error of 2 digits. Hence, it has to be ensured that no air bubbles cling to the solid immersed in the fluid. The same applies to the glass sinker that is immersed in the test fluid.
6.2.5 Glass Sinker for Measuring Fluids To save test fluids used for density determination of fluids, use a small glass beaker and an accordingly sized glass sinker. However, it needs to be pointed that a large glass sinker achieves higher accuracy. It is desirable that the buoyancy and the volume of the glass sinker are determined as accurately as possible. For the determination of fluid density these results are applied to the common denominator as well as the numerator of the formula. 6.
7 Density Table for Fluids Temperatur Density ρ [g/cm3] e [°C] Water Ethyl alcohol Methyl alcohol 10 0.9997 0.7978 0.8009 11 0.9996 0.7969 0.8000 12 0.9995 0.7961 0.7991 13 0.9994 0.7953 0.7982 14 0.9993 0.7944 0.7972 15 0.9991 0.7935 0.7963 16 0.9990 0.7927 0.7954 17 0.9988 0.7918 0.7945 18 0.9986 0.7909 0.7935 19 0.9984 0.7901 0.7926 20 0.9982 0.7893 0.7917 21 0.9980 0.7884 0.7907 22 0.9978 0.7876 0.7898 23 0.9976 0.7867 0.7880 24 0.9973 0.
8 Uncertainty of Measurement for Density Determination of Solids This table shows the approximate readability of the balance in connection with the density set. Observe that these values have only been determined by calculation and that influent parameters such as described in chapter 6 have not been taken into consideration. Approximate display at density measurements (when using a balance with a readability of 0.1 mg) Weight of sample (g) 1 5 10 100 200 300 1 0.001 0.0001 0.0001 0.0001 0.
9 User Instructions • To form a reproducible mean value several density measurements are necessary • Remove fat from solvent-resistant sample /glass sinker /beaker. • Regularly clean sample dishes/glass sinker/beaker, do not touch immersed part with your hands • Dry sample/glass sinker/pincers after each measurement. • Adjust sample size to sample dish (ideal sample size > 5 g). • Only use distilled water.
