KERN & Sohn GmbH
Ziegelei 1
D-72336 Balingen
E-Mail: info@kern-sohn.com
Phone: +49-[0]7433- 9933-0
Fax: +49-[0]7433-9933-149
Internet: www.kern-sohn.com
Operating instructions
Set for Density determination for
Analytical Balances KERN ACJ / ACS
KERN ACS-A03
Version 1.0
04/2012
GB
ACS-A03-BA-e-1210
2 ACS-A03-BA-e-1210
GB
KERN ACS-A03
Version 1.0 04/2012
Operating instructions
Density Determination Set for Analytical Balances
KERN ACJ / ACS
Contents:
1 INTRODUCTION ................................................................................................................................. 3
1.1 SCOPE OF DELIVERY .................................................................................................................. 3
2 PRINCIPLE OF DENSITY DETERMINATION ................................................................................... 5
2.1 INFLUENCING MAGNITUDES AND ERROR SOURCES ....................................................................... 6
3 INSTALLING THE DENSITY DETERMINATION SET ....................................................................... 7
4 DENSITY DETERMINATION OF SOLIDS ......................................................................................... 9
4.1 ACTIVATE "DENSITY DETERMINATION SOLID MATTER" MODE ......................................................... 9
4.2 CALCULATE DENSITY ...............................................................................................................11
4.3 DENSITY DETERMINATION OF SOLID MATERIAL WITH A DENSITY OF LESS THAN 1 G/CM3 ................12
5 DETERMINING DENSITY OF LIQUIDS ...........................................................................................13
5.1 DETERMINE VOLUME OF THE GLASS SINKER ..............................................................................13
5.2 CALL UP "DENSITY DETERMINATION FLUID" ................................................................................14
5.3 CALCULATE DENSITY ...............................................................................................................15
6 DATA-HOLD FUNCTION .................................................................................................................16
6.1 ACTIVATE FUNCTION ................................................................................................................16
6.2 HOLD / DELETE RESULT OF DENSITY DETERMINATION ON DISPLAY...............................................16
7 PRECONDITIONS FOR PRECISE MEASUREMENTS ................................................................17
7.1 CALCULATION OF RESULTS ......................................................................................................17
7.2 INFLUENCE FACTORS FOR MEASUREMENT ERRORS ..................................................................17
7.2.1 Air bubbles ........................................................................................................................17
7.2.2 Solid matter sample ..........................................................................................................17
7.2.3 Liquids ...............................................................................................................................18
7.2.4 Surface ..............................................................................................................................18
7.3 GENERAL INFORMATION ...........................................................................................................18
7.3.1 Density / Relative Density .................................................................................................18
7.3.2 Drift of Balance Display ....................................................................................................18
8 DENSITY TABLE FOR FLUIDS ....................................................................................................19
9 MEASUREMENT UNCERTAINTY DURING DENSITY DETERMINATION OF SOLID MATTER20
10 USER INSTRUCTIONS .................................................................................................................21
ACS-A03-BA-e-1210 3
1 Introduction
• In order to guarantee a safe and trouble-free operati on, pl ease
read carefully the operating instructions.
• These operating instructions only describe the operation of the
density determination s et. For further information on how to
operate your balance please refer to the operating instructions
supplied with each balance.
1.1 Scope of delivery
Check packaging and density determination set immediately when unpacking for
possible visible dam age.
Make sure that all parts are completely present.
Fig. 1 Scope of delivery
No. Description Number
(1) -1 Immer sion basket for descending solid matter (density > 1 g/cm³) 1
(1) -2 Immer sion basket for floati ng solid matter ( density < 1 g/cm³) 1
(2) Weighing tray holder 1
(3)
Glass container ∅ 90 mm, h = 60 mm
1
(4) Platform for glass c ontainer 1
(5)
Thermometer
1
(5) -1 Rubber stop for t hermometer 1
(6) Holder for thermometer 1
(7) Glass sinker 1
Operating instructions 1
(7)
4 ACS-A03-BA-e-1210
Fig. 2: Installed density set KERN ACS-A03
Fig. 3: Immersion basket for solid matter
A Upper sample dish (weight of the sample in air)
B Lower sample dish (weight of the sample in measuring liquid)
ACS-A03-BA-e-1210 5
ρ =
A
A-B
o
ρ
ρ =
m
V
2 Principle of Densi ty Determinati on
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 ].
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.
Additional frequently applied units include:
, ,
The application of this density determination set in combination with the KERN
ABS/ABJ balances provides fast and safe determ ination of solids and fluids. O ur set
uses the "Principle of A rchim edes" to determine density:
BUOYANCY IS A FORCE. IT AFFECTS A BODY THAT IS IMMERSED INTO A FLUID. THE
BUOYANCY OF THE BODY EQUALS THE WEIGHT FORCE OF THE DISPLACED FLUID. THE
FORCE OF BUOYANCY ACTS VERTICALLY UPWARDS.
Thus, density is calculated according to the formulae below:
To determine the densit y of solid matter
Our balances enable weighing of solids in air [ A ] as well as water [ B ]. If the density
of the buoyancy medium is known [ ρo ] the density of the solid [ ρ ] is calculated as
follows:
ρ = density of sample
A = weight of the sample in air
B = weight of sample in measuring fluid
ρ
o
= density of measuring fluid
1
g
cm
3
1
kg
m
3
1
g
l
6 ACS-A03-BA-e-1210
ρ =
V
A-B
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 for ce equal s t he w eight force of the fluid displaced by
the volume of the body.
The volume [ V ] of the immersed body equals the volum e of the displaced fluid.
G = buoyancy of sinker
Buoyancy of sinker =
Weight of the sinker in air [ A ] - weight sinker in sample liquid [ B ]
From this follows:
ρ = density of sample fluid
A = weight of sinker in air
B = weight of sinker in sample fluid
V = volume of sinker*
* If the volume of the sinker is unknown, this can be determined by a solid body
density measurement e.g. in water and be calculated as follows.
V = volume of sinker
A = weight of sinker in air
B = weight of sinker in water
ρ
W
= density of water
2.1 Influencing magnitudes and error sources
Air pressure
Temperature
Volume deviation of the sinker
Surface tension of the liquid
Air bubbles
Immersion depth of the sample dish of sinker
Porosity of the solid
ACS-A03-BA-e-1210 7
3 Installing th e den sity 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. Place the platform for glass
containers in a way that it does not
touch the balance tray holder.
5. Mount the immersion basket; ens ur e
that it hangs centrically in the recess
of the weighing tray holder.
8 ACS-A03-BA-e-1210
6. Close the glass doors. Connect
balance to power supply, the balance
will carry out a self-test. The balances
of the ACJ 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 auxiliary or
sample fluid.
9. Take away the immersion basket and put the glass container in the center of the
platform.
10. Remount the immersion basket. Make sure that it does not touch the glass
container.
11. Heat the liquid, the instruments or the sinker until the temperature is constant.
Observe the warm-up time of the balance.
ACS-A03-BA-e-1210 9
4 Density determination of solids
for the density determination of solid material, the solid is weighed first in air and then
in the auxiliary liquid. From the weight difference results the buoyancy from where
the software calculates the density.
4.1 Activate "density determination solid matter" mode
1. Call up menu:
In weighing mode press the MENU button
twice
2. Press the navigation buttons ( )
repeatedly until „APL.FUNC“ is displayed.
3. Press PRINT
4. Press the navigation buttons ( )
repeatedly until „SG“ is displayed. To
confirm, press TARE, "SET" followed by your
current setting will be displayed.
5. Press the cursor keys ( ) repeatedly until
“S.SG“ ("density determination solid matter")
is displayed.
Confirm with TARE. "SET" followed by the
currently set auxiliary fluid will be displayed.
6. Press the cursor keys ( ) repeatedly until
the desired auxiliary fluid is displayed.
Display Auxiliary fluid
Destilled water
Ethyl alcohol
Methyl alcohol
To use a different auxiliary fluid of your choice, select "OTHER".
To confirm, press TARE, "SET" followed by the display used to enter
"temperature auxiliary fluid" will appear.
10 ACS-A03-BA-e-1210
7. Press TARE and the display will change to
numeric data input.
The temperature currently set will be
displayed if water, ethanol or methanol is
selected.
On selecting "OTHER" the currently set
density of the fluid
Either
When selecting water, ethanol or methanol,
read the temperature at the thermometer or
enter it, using the cursor keys.
or
When selecting "OTHER" enter density of
auxiliary fluid of your choice.
Numeric input
#
indicates that the weighing balance is in
numeric input mode. The first digit is
flashing and can be changed.
Increase flashing dig it
Decrease flashing digi t
Digit selection to the right
Confirm entry
8. The weighing balance will display the
auxiliary fluid’s density at the entered
temperature for about 3 sec and will then
change to "density determination solid
matter" mode.
To change from density mode to weighing mode press MENU for 3 s.
ACS-A03-BA-e-1210 11
4.2 Calculate density
1. Check that "density determination solid
matter" mode is enabled (See chap. 4.1).
2. If weighing balance does not show Zero,
press TARE.
3. Put solid matter in top sample tray. The
weight of the „sample in air“ is displayed.
4. Wait un til stability display ( ) appears, then
press UNIT. "SINK" will be shown.
5. Put solid matter in lower sample tray and
press UNIT.
6. The weighing scale first determines, then
displays the solid matter’s density.
7. If you connect an optional printer you can
print the result.
8. Remove the sample. To carry out further
measuring, press UNIT, and then start with
step 2.
Printout example KERN YKB-01N:
KERN & Sohn GmbH
Company
TYPE ACS 320-4
Model
SN WB11AG0002
Serial no.
ID 1234
Balance identification no.
1.2188DS
Result
-SIGNATURE-
prepared by
- - - - - - - - - - - - - - - - -
12 ACS-A03-BA-e-1210
4.3 Density determination of solid material with a density of less than 1 g/cm
3
At solid material with density less than 1 g/cm3 , a density determ ination with two
different methods is poss ibl e.
Method 1:
As measuring density a liquid with less density than that of the solid material, e.g.
ethanol approx. 0.8 g/cm3.
This method should be applied when the density of the solid is just slightly different
from that of the distilled water.
Using ethanol is not recommended, when the solid material is being attacked.
When working with ethanol, you must observe the applicable safety regulations.
Method 2:
Here the sample is not placed upon, but under the lower sample dish. For this
purpose, use the immersion basket for floating solid matter [See chap. 1.1, no.(1)-2].
Activate "density determination solid matter" and enter the parameters for the
auxiliary fluid, see chap. 4.1.
Density measurement see chapter 4.2, in step 5 place the sample under the
sifting bowl. If the buoyancy of the sam ple is so much that the immersion basket
is lifted, place a dummy weight on it and tare it away when weighing in air.
ACS-A03-BA-e-1210 13
5 Determining densit y 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 Determine volume of the glass sinker
If the volume of the glass sinker is unknown, it must be determined and calculated as
follows.
1. Fill distilled water into the container and heat it until the temperature is constant.
Read temperature on the thermometer.
2. Call-up weighing mode. If weighing balance does not show Zero, press TARE.
3. Suspend the glass sinker. The weight of the drop shaft in air will be displayed.
4. Wait for the stability display ( ), then confirm by pressing TARE.
5. Place the water container on the platform and immerse the glass sinker. Wait for
stability display ( ). The balance displays the difference „weight in air – weight in
water“.
Note the value (without sign) and calculate the volume of the glass sinker according
to the following formula.
ρ
M
V =
V
= volume of glass sinker
M
= difference „weight in air – weight in water“
ρ
= density of water considering the temperature, see table 1.
Tab. 1: Density table of water
Temperature
[℃]
Density
ρ
[g/cm3]
Temperature
[℃]
Density ρ
[g/cm3]
Temperature
[℃]
Density ρ
[g/cm3]
10
0.9997
19
0.9984
28
0.9963
11
0.9996
20
0.9982
29
0.9960
12
0.9995
21
0.9980
30
0.9957
13
0.9994
22
0.9978
31
0.9954
14
0.9993
23
0.9976
32
0.9951
15
0.9991
24
0.9973
33
0.9947
16
0.9990
25
0.9971
34
0.9944
17
0.9988
26
0.9968
35
0.9941
18
0.9986
27
0.9965
14 ACS-A03-BA-e-1210
5.2 Cal l up "de nsity determination fluid"
1. Call up menu:
In weighing mode press the MENU button
twice.
2. Press the navigation buttons ( )
repeatedly until „APL.FUNC“ is displayed.
3. Press PRINT
4. Press the navigation buttons ( )
repeatedly until „SG“ is displayed. To
confirm, press TARE, "SET" followed by
your current setting will be displayed.
5. Press the cursor keys ( ) repeatedly
until “L.DENS“ ("density determination fluid"
mode) appears. Confirm with TARE. "SET",
followed by the display used to enter the
drop shaft volume will appear.
6. Press TARE and the display will change to
numeric data input.
#
indicates that the weighing balance is in
numeric input mode. The first digit is
flashing and can be changed.
Using the cursor keys, enter the drop
shaft’s volume (See chap. 5.1).
Numeric entry
Increase flashing dig it
Decrease flashing digi t
Digit selection to the right
Confirm entry
7. The weighing balance will show “SET“ for
about 3 sec. after which it will change to
"density determinati on fluid" mode.
To change from density mode to weighing mode press MENU for 3 s.
ACS-A03-BA-e-1210 15
5.3 Calculate density
1. Pour test fluid into glass container.
Check that "density deter min at ion fl ui d "
mode is enabled (See chap. 5.2).
2. If weighing balance does not show Zero,
press TARE.
6. Suspend the glass sinker. The weight of the
drop shaft in air will be displayed.
7. Wait until stability display ( ) appears, then
press UNIT. "SINK" will be shown.
3. Put glass container with test fluid onto pan.
Immerse glass container completely in the
fluid, trying to avoid bubble formation. Press
UNIT.
4. The weighing balance will first determine
then display the fluid’s densit y .
5. If you connect an optional printer you can
print the result.
Printout example KERN YKB-01N:
KERN & Sohn GmbH
Company
TYPE ACS 320-4
Model
SN WB11AG0002
Serial no.
ID 1234
Balance identification no.
0.1109DL
Result
-SIGNATURE-
prepared by
- - - - - - - - - - - - - - - - -
For further measurements
Clean and dry container and glass sinker carefully.
Suspend again the glass sinker
Press the UNIT-key
Start with step 2
16 ACS-A03-BA-e-1210
6 Data-Hold function
The data hold function may be acti v at ed duri n g the density determination o f soli d
matter as well as during the density determination of fluids.
The displayed density value quite often fluctuates and is hard to read. By enabling
the data hold function, the density value will be kept on display after stationary
control until the UNIT key is operated.
6.1 Activate function
1. Call up menu:
In weighing mode press the MENU button
twice.
2. Press the navigation buttons ( )
repeatedly until „APL.FUNC“ is displayed.
3. Press PRINT
4. Press the navigation buttons ( )
repeatedly until „SG“ is displayed. To
confirm, press TARE, "SET" followed by
your current setting will be displayed.
5. Press the navigation buttons ( )
repeatedly until „SG HOLD“ is displayed.
Confirm with TARE.
The indicator shows that the data hold
function has been enabled.
6. To return to density determin ati on m ode ,
press ON/OFF repeatedly.
6.2 Hold / delete result of density determination on display
To carry out density determination, see chap.4.2 /step 6 or chap.5.3 /step 4.
“WAIT“, will be flashing for about 5 sec whilst weighing balance is determining
density.
[∗] indicates the recorded densi ty.
To delete the retained display value, press the UNIT key. The balance returns to
density determination mod e.
ACS-A03-BA-e-1210 17
ρ =
A
o
ρ
7 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.
7.1 Cal culation 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. Therefore all weighing results
used for calculations have to be examined closely.
Example for density determination of solids:
To ensure high-grade results, numerators as well as common denominators of the
formula below must show the desired accuracy. If either of them is instable or flawed,
the result, too, will be instable or flawed.
ρ = density of sample
A = weight of the sample in air
B = weight of the sample in the aid liquid
ρ
o
= density of the aid liquid
7.2 Influence Factors for Measurement Errors
7.2.1 Air bubbles
A small bubble with a diameter of 1 mm results in a raise of 0.5 mg, while those with
2 mm Ø already produce a raise of 4 mg.
Therefore, make sure that no air bubbles adhere on the solid object or sinker that is
immersed in the liquid.
An oily surface causes air bubbles when immersing in the liquid, so
Remove grease from solvent resistant solid matter sample
clean all parts that are immersed regularly and don't touch them with bare
fingers
Don't lay solid samples (particularly flat objects) outside of the liquid on the sample
bowl, because this results in air bubbles by the joint immersion.
7.2.2 Solid matter sample
A sample possessing too great a volume that is immersed in fluid will r esul t in an
increase in fluid level inside the glass pitcher. As a result, part of the suspension
bracket of the sample dish will also be immersed causing buoyancy to increase. As a
consequence the weight of the specimen in the fluid will drop.
Samples that change the volume or assimilate fluid are unsuitable for measurement.
18 ACS-A03-BA-e-1210
7.2.3 Liquids
Solids are generally not sensitive to temperature changes, so that the corresponding
density changes are not relevant. However, since you work with an aid liquid by the
density determination of solids, according to the "Archimedean Principle", its
temperature is taken into account. The temperature change effects liquids greater
and causes changes in the density in order of 0.1 to 1 ‰ per °C. Hereby, the third
digit after the decimal point is a ffec te d.
7.2.4 Surface
The suspension bracket of the sample dish penetrates the surface of the fluid. This
state undergoes continuous change. If the sample or the sinker is relatively small, the
surface tension will impair repeatability. Adding a small amount of Tensid (detergent)
makes surface tension negligible and increases reproducibility.
7.3 Ge neral information
7.3.1 Density / Relative Density
Relative density follows from the weight of a specimen divided by the weight of water
(at 4° Celsius) of the same volume. For this reason relative density does not have a
unit. Density equals mass divided by volume.
The application of the relative density instead of the density of a fluid in a formula
produces an incorrect result. In the case of fluids only their density is
physically meaningful.
7.3.2 Drift of Balance Display
The drifting of a balance does not influence the final result of the density
determination although the shown weight of weighing in air is affected. Accurate
values are merely required if the density of fluids is determin ed by means of a sinker.
When changing the ambient temperature or location, an adjustment of the balance is
necessary. For this purpose, remove the density set and carry out adjustment using
the standard weighing pan.
ACS-A03-BA-e-1210 19
8 Density Table for Fluids
Temperature
[°C]
Density ρ [g/cm
3
]
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
0.7859
0.7870
25
0.9971
0.7851
0.7870
26
0.9968
0.7842
0.7861
27
0.9965
0.7833
0.7852
28
0.9963
0.7824
0.7842
29
0.9960
0.7816
0.7833
30
0.9957
0.7808
0.7824
31
0.9954
0.7800
0.7814
32
0.9951
0.7791
0.7805
33
0.9947
0.7783
0.7896
34
0.9944
0.7774
0.7886
35
0.9941
0.7766
0.7877
20 ACS-A03-BA-e-1210
9 Measurement uncertainty during density
determination of solid matter
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 parameter s such as described in chapter 7 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)
Density of sample [g/cm3]
1 5 10 100 200 300
1 0.001 0.0001 0.0001 0.0001 0.0001 0.0001
3 0.002 0.0004 0.0003 0.0001 0.0001 0.0001
5 0.003 0.001 0.0004 0.0002 0.0002 0.0002
8 0.004 0.001 0.0006 0.0003 0.0003 0.0003
10 0.005 0.001 0.0008 0.0004 0.0003 0.0003
12 0.006 0.002 0.001 0.0004 0.0004 0.0004
20 0.01 0.003 0.001 0.001 0.001 0.001
Reading example for table:
In a balance with a resolution of 0.0001 g and a sample with a weight of 5 g, whose
density is 3 g/cm3, the display graduation is at 0.0004 g/cm3.
ACS-A03-BA-e-1210 21
10 User Instructions
• To form a reproducible mean value several density measurement 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.
• When immersing for the first time, lightly shake sample dishes and sinker, in order
to Dissolve air bubbles.
• Always ensure that, when re-immersing into the liquid no additional bubbles
adhere; it is better to use pincers to place the sample.
• Remove firmly adherent air bubbles with a fine brush or a similar tool.
• To avoid adherent air bubbles smoothen samples with rough surface.
• Take care that no water drips onto the upper sample dish when weighing with the
help of tweezers.
• In order to reduce the surface tension of water and the friction of the liquid on the
wire, add three drops of a common detergent (washing-up liquid) to the
measuring liquid (density modification of dest. water occurring due to the addition
of tensides can be ignored).
• Oval samples can be held more easily with pincers when you cut grooves into
them.
• The density of porous solids may only be determined approximately. Buoyancy
errors occur when not all the air is eliminated from the pores during immersion in
the measuring fluid.
• To avoid great vibrations of the balance, place sample carefully.
• Avoid static charge, e. g. dry glass sinker with cotton cloth only.
• If the density of your solid only deviates slightly from that of distilled water,
ethanol may be used as measuring fluid. However, check beforehand whether the
sample is solvent-proof. In addition you must observe the applicable safety
regulations when working with ethanol.
• Handle glass sinker with care (no warranty claims in case of damage ).
• To avoid corrosion, don't leave the density set immersed in liquid for a long time.
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