KERN PBS-A03 User manual

KERN & Sohn GmbH
Ziegelei 1
D-72336 Balingen
email: [e-mail]
Phone: +49-[0]7433- 9933-0
Fax: +49-[0]7433-9933-149
Internet: www.kern-sohn.com
Operating instructions
Density Determination Set
KERN PBS-A03/A04
Version 1.3
01/2012
GB
PBS-A03/A04-BA-e-1213

2 PBS-A03/A04-BA-e-1213
GB
KERN PBS-A03/A04
Version 1.301/2012
Operating instructions
Set for density determination for precision balances
KERN PBJ/PBS
Contents:
1INTRODUCTION ............................................................................................................................ 3
1.1 SCOPE OF SUPPLY.................................................................................................................... 3
1.2 DIMENSIONS............................................................................................................................. 5
2INSTALLING THE DENSITY DETERMINATION SET.................................................................. 6
3PRINCIPLE OF DENSITY DETERMINATION............................................................................... 8
3.1 INFLUENCING MAGNITUDES AND ERROR SOURCES...................................................................... 9
4DENSITY DETERMINATION OF SOLIDS................................................................................... 10
4.1 ACTIVATE FUNCTION............................................................................................................... 10
4.2 INPUT „DENSITY MEASURING LIQUID“ ....................................................................................... 11
4.3 MEASUREMENT „DENSITY SOLID MATERIAL“............................................................................. 12
5DETERMINING DENSITY OF LIQUIDS ...................................................................................... 13
5.1 VOLUME DETERMINATION OF THE SINKER................................................................................. 13
5.2 DENSITY DETERMINATION AT KNOWN VOLUME OF THE SINKER................................................... 14
6PRECONDITIONS FOR PRECISE MEASUREMENTS............................................................... 16
6.1 CALCULATION OF RESULTS..................................................................................................... 16
6.2 INFLUENCE FACTORS FOR MEASUREMENT ERRORS ................................................................. 17
6.2.1 Air bubbles....................................................................................................................... 17
6.2.2 Solid body sample ........................................................................................................... 17
6.2.3 Liquids.............................................................................................................................. 17
6.2.4 Surface............................................................................................................................. 17
6.2.5 Sinker for liquid density measurement ............................................................................ 17
6.3 GENERAL INFORMATION.......................................................................................................... 18
6.3.1 Density / Relative Density................................................................................................ 18
6.3.2 Drift of Balance Display ................................................................................................... 18
7DENSITY TABLE FOR FLUIDS................................................................................................... 19
8UNCERTAINTY OF MEASUREMENT FOR DENSITY DETERMINATION OF SOLIDS............ 20
9USER INSTRUCTIONS................................................................................................................ 21

PBS-A03/A04-BA-e-1213 3
1 Introduction
KERN PBS-A03 KERN PBS-A04
•Set for density determination for
precision balances of the series
KERN PBJ/PBS with big weighing
plate (180 x 170 mm).
•Set for density determination for
precision balances of the series
KERN PBJ/PBS with small
weighing plate (105 x 105 mm).
•When using the density set, the
capacity of the balance is reduces
by approx. 100 g.
•When using the density set, the
capacity of the balance is reduces
by approx. 290 g.
•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
Fig. 1: Installed density set KERN PBS-A04

4 PBS-A03/A04-BA-e-1213
1. Weighing tray holder
2. Combination weighing tray
3. Container table
4. Container
5. Weighing tray carrier,
4 items
6. Glass sinker

PBS-A03/A04-BA-e-1213 5
1.2 Dimensions

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2 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.
•The following pictures show the density set KERN PBS-A03 at a balance with
big weighing plate. The density set KERN PBS-A04 must be installed at the
same way.
1. Switch off balance and separate it from the power supply.
2. Remove standard weighing plate.
3. Remove carrier of the standard
weighing plate and replace by
weighing tray carrier of the density
set.
4. Put balance tray holder according to
fig. into the four balance tray carriers.
Thereby observe the right position,
the openings on the upper side must
point forwards.

PBS-A03/A04-BA-e-1213 7
A
B
5. Place the container table in a way
that it does not touch the balance tray
holder.
6. Put the containers in the center of the
container table
7. Hook up the combination balance
tray according to illustration; ensure
that it does not touch the container.

8 PBS-A03/A04-BA-e-1213
ρ = A
A-B o
ρ
ρ =
m
V
3 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 ].
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:
1g
cm
3
,
1kg
m3
,
1g
l
The application of this density determination set in combination with the KERN PBS/PBJ
balances provides fast and safe determination of solids and fluids. Our set uses the
"Principle of Archimedes" 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:
Determining density of solid bodies
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
ρo = density of measuring fluid

PBS-A03/A04-BA-e-1213 9
ρ =
V
A-B L
ρ
+
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 test 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.
G = buoyancy of sinker
Buoyancy of sinker =
Weight of the sinker in air [ A ] -weight sinker in test liquid [ B ]
From this follows:
ρ= Density of test liquid
A = weight of sinker in air
B = weight of sinker in sample fluid
V = volume of sinker*
ρL = Air density (0.0012 g/cm³)
* If the volume of the sinker is unknown, this can be determined e.g. in water and be
calculated as follows, see chap. 5.1.
V = volume of sinker
A = weight of sinker in air
B = weight of sinker in water
ρW = density of water
3.1 Influencing magnitudes and error sources
Air pressure
temperature
Volume deviance of the sinker (±0,005 cm3)
Surface tension of the liquid
Air bubbles
Immersion depth of the sample dish of sinker
Porosity of the solid

10 PBS-A03/A04-BA-e-1213
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.
Prepare balance as described in chapter 2 "Installation of density determination
set".
Fill measuring liquid into the container. Filling height should be approx. ¾ of the
capacity. Heat measuring liquid until temperature is constant.
4.1 Activate function
Switch on balance
In weighing mode press repeatedly
MENU
CAL
until
„U“ flashes.
Press
TARE/
Press repeatedly
MENU
CAL
until „U-

d“ is
displayed.
From now on the balance is in density
determining mode for solids.