Training Material for Balances(1) Prepared by R&D Division 1

A&D Company,Company Limited1ContentsThings you should know before using a balance --------------------------- P.3––––––––

Maximum Permissible Errors On Initial Verification & In Service ----- P.21––

1. Convection Flow ------------------------------ P.4
2. Tilting ------------------------------------------- P.6
3 Static Electricity ------------------------------- P.83.
P8
4. Magnetic Material ----------------------------- P.13
5. Air Current (Wind) ---------------------------- P.14
6. Vibration ---------------------------------------- P.15
7 A
7.
Accelerationl ti off Gravity
G it ----------------------- P.16
P 16
8. Buoyancy --------------------------------------- P.20
Example of GP-30K ----------------------------- P.22
Maximum Permissible Errors ------------------ P.23

Validations ----------------------------------------------------------------------- P.25–––

What Is Validation? ------------------------------ P.26
Items To Be Recorded --------------------------- P.27
IQ, OQ, PQ ---------------------------------------- P.28

2

Things you should know
before using a balance31. Convection FlowA)) Effects of Convection Flows
If the surface of the sample (object to be measured) ish tt thanhotter
th theth ambient
bi t temperature,tt
an ascending
di airicurrent will be generated near the sample.
A bi Temp.
Ambient
T20℃

40℃

Convection
Flow

Since this air current will lift up the sample, the balance
will display a weight that is lighter than the actualsample.
pAs the sample cools down and the convection flow
becomes weaker, the displayed weight will gradually
increase, making the balance appear unstable.
41. Convection FlowB)) Preventingg Convection FlowsWait until the sample and the tare are balanced with the ambient
temperature.
Refrain from directly touching the sample or the tare. Use tweezers
instead.
instead
Do not place the balance where there could be a rapid temperaturechangeg (e.g.
( g near a window,, under direct sunlight,g , etc.))
If a temperature change is inevitable, take countermeasures such as
shielding the balance from the surrounding heat, etc.

5

2. TiltingA) Effects of Tilting
When a balance
Whb lisi placedl d horizontally,h i t ll it detects
d t t theth gravitational
it ti l force
fthatth t isi
applied to the sample vertically.
oweve , if thet e balanceba a ce iss placedp aced ono a slope,s ope, thet e gravitationalg av tat o a forceo ce applied
app ed to thet e
However,sample will be broken down to the longitudinal and lateral directions of thebalance. As the balance detects only the longitudinal force, it will display a smaller
value than the actual weight of the sample.
sampleTh forceThefthatth t cannott beb detectedd t t dθ

Displayed value

Gravitational force = Displayed value

θ Gravitational force

62. TiltingB) To Avoid TiltingLevel the balance using its leveling feet.
If levelingl li isi difficult,diffi lt calibrate
lib t theth balanceb lin
i theth currentt
position.

73. Static Electricity
A) Problems due to Static Electricity
When the sample is electrostatically charged, the sample and the objects
surrounding the sample will attract each other. This makes an accurate
measurement difficult.
difficult Moreover,Moreover the static electricity moving into the air or
the weighing pan over time will cause a gradual change in the displayed value.
+‐

Attraction‐+‐

Attraction+++++ ++++ +

‐

‐

‐

‐

‐

‐

‐

Measuring acharged object

There is a charged
object nearby

When a charged object comescloser, the opposite electricity
will be generated in thesurrounding objects.
Consequently, the charged
object and the surrounding
objects will attract each other.
(Dielectric Polarization)
83. Static Electricity
In winter, for example, operators wearing sweaters can beelectrostatically charged. When electrostatically charged
operators use an electronic balance, the displayed value may
wellll becomebunstable.
t blA&D s analytical balances are equipped with a breeze break
A&D’s
whose surface has an evaporated thin metal layer to shield thechamber from outside static electricity. Our resin breeze
breaks are also coated with antistat.

9

3. Static Electricity
B) Causes of Static ElectricityContact electrification occurs when two objects make contact with each other.
Frictional electrification occurs when objects are rubbed together.
Peel electrification occurs when peeling something off from an object.
Impact electrification occurs when objects collide with each other.
Materials susceptible to static electricity- resin, glass, powder, insulators such as film and paper
Places where static electricity is easily generated- production lines or belt conveyers, dried places, etc.
It is widely believed that little static electricity occurs where the humidity is
kept higher than 45%RH. In actuality, static electricity often exists where
there is constant friction, such as on production lines and belt conveyers.

103. Static Electricity
C) Preventing Static Electricity
Two principal measures to prevent static electricity are removal
and shielding.
Metal shield‐‐

Attraction+++‐+++‐



+‐



Eliminate the static electricity using
AD-1683
Enclose the charged object with a metal
tare to block the electricity
Apply an antistatic agent
Raise the humidity (not lower than45%RH)
11

3. Static Electricity
D) Troubles caused by Static Electricity(Case 1)
IIn a production
d ti line
li off secondary
dbatteries,b tt i frictionalf i ti l electrificationl t ifi ti tookt k placelbetweenb t
thethstainless secondary batteries and resin jigs, causing a zero drift on AD-4212A-200. Simply
placing AD-1683 near the weighing sensor solved the problem.

(Case 2)In an application process of cream solder where the discharge rate was periodicallychecked with AD-4212A-100, there was a resin breeze break near the weighing sensor.
This breeze break was electrostatically charged and was making the weighing value
unstable. Again, AD-1683 solved the problem.

(Case 3)We received a complaint from a GP-12K user saying that the counting mode was not stableenough, and that even A&D’s repair service did not fix the problem. It was later found thatthey were counting resin components placed in a resin bowl,
bowl near the entrance of abuilding. In addition to avoiding the wind from the entrance, we recommended using AD1683, wrapping the bowl with an aluminum foil, or applying antistat.

12

4. Magnetic MaterialA) Influence of Magnetic MaterialsWhen measuring a magnetic material or a magnetized sample, it may attract
and be attracted to the surrounding components of the balance, or be influenced
byy the magnetic
gforce of the sensor coil. This will lead to inaccurate weighing
g gresults.

B) Measures
Mto counter M
Magnetici M
Materials
i l
Keepp a distance between the sample
p and the balance.
- Use the underhook and increase the distance between thesample and the balance.
- CoverCtheth sample
l withith highly
hi hl permeable,
bl soft
ft magnetic
ti material,t i lsuch as permalloy (magnetic shielding).
13

5. Air Current (Wind)
A) Influence of Air Currents
Weighing becomes unstable when the weighing pan or the sample are subject
to wind. Even an air current that is too weak for a human to sense can easily
make the measurement unsteady.
Places where Air Currents often occur
Near an air conditioner, near a doorway, near a passageway, wherever there is attemperaturetchangehB) Measures to counter Air Currents
Change the location and install the balance where the influence of the air
current is insignificant.
Att h a breeze
Attachbbreakb k andd preventt theth direct
di t contact
t t off theth wind.
i d(Caution: There is a possibility of static electricity depending on the material
the breeze break is made from.)

14

6. VibrationA) Influence of Vibrations
Weighing becomes unstable when the balance is subject to vibrations. Low
Lowfrequency vibrations are especially troublesome.
Situations in which Vibrations often occur- On the 2nd floor or higher of a building- Windy days
- In an earthquake
earthquake-proof
proof building after there is an earthquake- Unstable ground (reclaimed land, riverside, seaside, etc.), especially on a windy day- Seaside, on a day of high waves

B) Measures to counter Vibrations


Set the response speed at “SLOW”
Install the balance on an anti-vibration table, such as AD-1685
15

7. Acceleration of Gravity
A) What is Gravity?
NorthPoleCentrifugal force

Universal
gravity
Gravitationalforce
E tEquator

Objects on the earth are constantly
subject to the “universaluniversal gravity,”
gravity,which attracts them toward thecenter of the earth, as well as the“centrifugal force” caused by therotation of the earth.
The gravitational force is theresultant of the universal gravity
and the centrifugal force.
force
16

7. Acceleration of Gravity
The “magnitude of the gravitational force” (F) is the product of the““accelerationl ti off gravity”
it ” (g)( ) andd theth “mass“off theth object”
bj t” (m).
( )

F=mg
g
In fact, what electronic balances measure is the gravitational force on
the sample
sample. Therefore,
Therefore if the acceleration of gravity varies,
varies thedisplayed value will also vary.

The acceleration of gravity varies with latitude and altitude.

17

7. Acceleration of GravityB) Changes in the Acceleration of Gravity
Changes by latitude
Earth’s rotation generates the centrifugal force, which counteracts theuniversal gravity. The centrifugal force becomes larger closer to theequator.
t InI contrast,t t theth accelerationl ti off gravity
it becomesbsmallerll closer
ltot
the equator.

Changesg byy altitude

Altitude
Earth’s radius

If the latitude is the same, the higher the altitude, the longer the distancefrom the center of the earth. Hence, the acceleration of gravity is alsosmaller. For instance, if a weight measured on the ground is 500g, is thenmeasured at an altitude of 100m,2
Earth' s radius  499.9843 g
500.000 g Earth' s radius  100m 2* On the premise that the earth’s radius is 6,371,000m
18

7. Acceleration of GravityC) Influence of the Acceleration of Gravity
What happens
ppwhen a balance calibrated with a 100.0000gg weightg at our Kensei
factory is brought to a different location?

Location
Helsinki
Paris
Kensei Factory
T kTokyoSingapore

Acceleration
off Gravity
G it(m/sec 2 )Displayed
Value(g)Difference fromKensei Factory
（ｇ）

9.819
9.809
9.800
9 798
9.798
9.781

100.1939
100.0918
100.0000
99 9796
99.979699.8061

0.19390.09180.0000-0.0204
0 0204-0.1939

To avoid these variances,variances a balance with a high resolution needs calibration at the pointof use. In case of a scale with a lower resolution, select a preset acceleration of gravity
according to the area of use.

19

8. Buoyancy
Air has a density of approximately 1.2kg/m3 and therefore analytical balances
are affected by buoyancy.
Ex)

Measuring a 200g stainless steel weight (density 8g/cm3) when barometricpressure is 1000hPa and air density is 0.0012g/cm3
Effect of Buoyancy  Air Density  Volume of the Weight 0.0012g/cm 3  200g  8g/cm 3
 0.03g

If barometric pressure changes to 980hPa, the error due to buoyancy is:
Error due to Buoyancy  0.03g  0.03g 980hPa
1000hPa 0.6mg

For example, suppose we calibrate a balance using a 200g weight when the barometricpressure isi 1000hPa.
1000hP If th
the nextt dday th
the bbarometrict i pressure iis 980hP
980hPa, th
the bbalancelwillill
display 200.0006g for the same 200g weight.
20

Maximum Permissible Errors
On Initial Verification & In Service

21

Example of GPGP-30K*
Accuracy Class of GP-30K- Maximum Capacity:
Max = 30kg
Max.
- Verification Scale Interval:
e = 1g- Actual Scale Interval:
d = 0.1g- NumberN b off VVerification
ifi ti Scale
S l Intervals:
I tl
n = 30,000g/1g
30 000 /1 = 30,000
30 000(n = maximum capacity/verification scale interval)
According to the principles of classification prescribed by the OIML, if theVerification scale interval is:
N b off verification
Numberifi ti scalel intervals
i tl is:i0.1g ≤ e
5 000 ≤ n ≤ 100,000
5,000
100 000

then the accuracy class should be Class II.

* Verification model22

Maximum Permissible Errors
For Class II(GP-30K: Max. = 30kg, e = 1g, d = 0.1g)

Number of Verification Scale Intervals
0 ≤ n ≤ 5,000
5,000 < n ≤ 20,00020,000 < n ≤ 100,000

0kg ~ 5kg
5kg ~ 20kg
20kg ~ (31kg)

Maximum Permissible Errors
On Initial Verification
In Service
0.5e
1.0e
1.5e

0.5g
1.0g
1.5g

1.0g
2.0g
3.0g

23

Maximum Permissible Errors
For corner (eccentric) loading, the indications must meet the maximum
permissible errors on initial verification when a load corresponding to 1/3 of themaximumicapacity
i is
i appliedli d at fourfpositions,ii
half
h lf theh distancedifromf
theh center(e.g. 10kg for GP-30K).
The maximum permissible errors in service shall be twice the maximum
permissible errors on initial verification.
3.0g
g

3.0gg

2.0g

2.0g

1.0g

1.0g

0g

0g

-1.0g

-1.0g

-2.0g

-2.0g

-3.0g

-3.0g
10kg

20kg

On initial verification

30kg

10kg

20kg

In service

30kg

24

Validations

25

What Is Validation?
Requirements come from Pharmaceutical Industries
All drugs sold in the U.S. must be certified by the FDA (U.S. Food and Drug
Administration) and be manufactured in compliance with GMP. Hence, GMP
has become the national standard for all pharmaceutical companies.
 GLP– Good Laboratoryy Practice– Regulation related to the safety inspection of medicine– GLP assures quality and reliability of inspection data.
 GMP– Good Manufacturing Practice– Standard related to the pproduction of medicine and quality
qy control– GMP assures that products have a certain level of quality.
26

Items To Be Recorded Why, how and by whom the work was done Who was in control
 What equipment was used
 What results were obtained What problems were encountered How those problems were overcome

IQ =OQ =PQ =Installation Qualification
Operational Qualification
Performance Qualification
27

IQ, OQ, PQ
Installation Qualification– Check if…
 The
Th deliveredd lid equipment
iisi ini accordancedwithi h theh requestedd design
d iand specifications.
 The equipment has been installed under proper conditions.
 The
Th environment
it isi adequate
dt forf theth equipment.
it

Operational Qualification– Check if…
 The equipment, installed under proper conditions, operates properly(not required to satisfy the manufacturer’s specifications).

Performance Qualification– Prove that the equipment consistently maintains a certain level ofperformance when it is used for inspecting actual samples– Assure that the equipment consistently provides reliable andaccurate measurements in daily analyses

28