SIST EN ISO 8655-6:2002

SLOVENSKI STANDARD
SIST EN ISO 8655-6:2002
01-november-2002
9ROXPHWULþQHQDSUDYHGHOXMRþHQDEDWGHO*UDYLPHWULþQHPHWRGH]D
GRORþHYDQMHQDSDNHSULPHUMHQMX,62
Piston-operated volumetric apparatus - Part 6: Gravimetric methods for the determination
of measurement error (ISO 8655-6:2002)
Volumenmessgeräte mit Hubkolben - Teil 6: Gravimetrische Prüfverfahren zur
Bestimmung der Messabweichung (ISO 8655-6:2002)
Appareils volumétriques a piston - Partie 6: Méthodes gravimétriques pour la
détermination de l'erreur de mesure (ISO 8655-6:2002)
Ta slovenski standard je istoveten z: EN ISO 8655-6:2002
ICS:
17.060 Merjenje prostornine, mase, Measurement of volume,
gostote, viskoznosti mass, density, viscosity
71.040.20 Laboratorijska posoda in Laboratory ware and related
aparati apparatus
SIST EN ISO 8655-6:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 8655-6:2002

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SIST EN ISO 8655-6:2002
EUROPEAN STANDARD
EN ISO 8655-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2002
ICS 17.060
English version
Piston-operated volumetric apparatus - Part 6: Gravimetric
methods for the determination of measurement error (ISO 8655-
6:2002)
Appareils volumétriques à piston - Partie 6: Méthodes Volumenmessgeräte mit Hubkolben - Teil 6:
gravimétriques pour la détermination de l'erreur de mesure Gravimetrische Prüfverfahren zur Bestimmung der
(ISO 8655-6:2002) Messabweichung (ISO 8655-6:2002)
This European Standard was approved by CEN on 13 July 2002.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 8655-6:2002 E
worldwide for CEN national Members.

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SIST EN ISO 8655-6:2002
EN ISO 8655-6:2002 (E)
Foreword
This document (ISO 8655-6:2002) has been prepared by Technical Committee ISO/TC 48
"Laboratory glassware and related apparatus" in collaboration with Technical Committee
CEN/TC 332 "Laboratory equipment", the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication
of an identical text or by endorsement, at the latest by March 2003, and conflicting national
standards shall be withdrawn at the latest by March 2003.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the
United Kingdom.
Endorsement notice
The text of the International Standard ISO 8655-6:2002 has been approved by CEN as a
European Standard without any modifications.
NOTE Normative references to International Standards are listed in Annex ZA (normative).
2

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SIST EN ISO 8655-6:2002
EN ISO 8655-6:2002 (E)
Annex ZA (normative)
Normative references to international publications with their relevant European
publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and
the publications are listed hereafter. For dated references, subsequent amendments to or
revisions of any of these publications apply to this European Standard only when incorporated
in it by amendment or revision. For undated references the latest edition of the publication
referred to applies (including amendments).
NOTE Where an International Publication has been modified by common modifications,
indicated by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
EN ISO 3696 1995 Water for analytical laboratory use - ISO 3696 1987
Specification and test methods
3

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SIST EN ISO 8655-6:2002

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SIST EN ISO 8655-6:2002
INTERNATIONAL ISO
STANDARD 8655-6
First edition
2002-09-15
Piston-operated volumetric apparatus —
Part 6:
Gravimetric methods for the determination
of measurement error
Appareils volumétriques à piston —
Partie 6: Méthodes gravimétriques pour la détermination de l'erreur de
mesure

Reference number
ISO 8655-6:2002(E)
© ISO 2002

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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
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©
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 2
5 Test liquid . 2
6 Test conditions . 2
7 Procedure . 3
8 Evaluation . 8
9 Test report . 10
Annexes
A Calculation of volumes from balance readings . 12
B Assessment of the uncertainty of the delivered volume. 13
Bibliography. 14
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 8655 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 8655-6 was prepared by Technical Committee ISO/TC 48, Laboratory glassware and
related apparatus, Subcommittee SC 1, Volumetric instruments.
ISO 8655 consists of the following parts, under the general title Piston-operated volumetric apparatus:
— Part 1: Terminology, general requirements and user recommendations
— Part 2: Piston pipettes
— Part 3: Piston burettes
— Part 4: Dilutors
— Part 5: Dispensers
— Part 6: Gravimetric methods for the determination of measurement error
The following part is under preparation:
— Part 7: Non-gravimetric methods for the determination of measurement error
Annex A forms a normative part of this part of ISO 8655. Annex B is for information only.
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
Introduction
ISO 8655 addresses the needs of:
— suppliers, as a basis for quality control including, where appropriate, the issuance of supplier's declarations;
— test houses and other bodies, as a basis for independent certification;
— users of the equipment, to enable routine checking of accuracy.
The tests specified should be carried out by trained personnel.
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SIST EN ISO 8655-6:2002

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SIST EN ISO 8655-6:2002
INTERNATIONAL STANDARD ISO 8655-6:2002(E)
Piston-operated volumetric apparatus —
Part 6:
Gravimetric methods for the determination of measurement error
1 Scope
This part of ISO 8655 specifies the reference method for conformity testing of piston-operated volumetric apparatus,
whereby errors of measurement are determined gravimetrically. The tests are applicable to complete systems
comprising the basic apparatus and all parts selected for use with the apparatus, disposable or reusable, involved in
the measurement by uptake (In) or delivery (Ex) process.
NOTE General requirements and definitions of terms of piston-operated volumetric apparatus are given in ISO 8655-1. For the
metrological requirements, maximum permissible errors, requirements for marking and information to be provided for users for
piston-operated volumetric apparatus, see ISO 8655-2 for piston pipettes, see ISO 8655-3 for piston burettes, see ISO 8655-4 for
dilutors and see ISO 8655-5 for dispensers. Alternative test methods such as photometric and titrimetric methods will be the
subject of a future Part 7 to ISO 8655.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 8655. For dated references, subsequent amendments to, or revisions of, any of these publications do
not apply. However, parties to agreements based on this part of ISO 8655 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated references,
the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of
currently valid International Standards.
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 8655-1:2002, Piston-operated volumetric apparatus — Part 1: Terminology, general requirements and user
recommendations
ISO 8655-2:2002, Piston-operated volumetric apparatus — Part 2: Piston pipettes
ISO 8655-3:2002, Piston-operated volumetric apparatus — Part 3: Piston burettes
ISO 8655-4:2002, Piston-operated volumetric apparatus — Part 4: Dilutors
ISO 8655-5:2002, Piston-operated volumetric apparatus — Part 5: Dispensers
ISO/TR 20461:2000, Determination of uncertainty for volume measurements made using the gravimetric method
ISO/IEC Guide 2, Standardization and related activities — General vocabulary
OIML R 76-1:1992, Non-automatic weighing instruments — Part 1: Metrological and technical requirements — Tests
3 Terms and definitions
For the purposes of this part of ISO 8655, the terms and definitions given in ISO 8655-1, ISO/IEC Guide 2 and
OIML R 76-1 apply.
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
4 Apparatus
4.1 Analytical balance or equivalent weighing device, with a resolution appropriate to the selected volume of
the apparatus under test (see Table 1).
Table 1 — Minimum requirements for balances
a
Selected volume of apparatus under Repeatability and Standard uncertainty of
Resolution
test linearity measurement
V mg mg mg
1µl�V � 10µl 0,001 0,002 0,002
10µl 100µl 1ml 10 ml a
For practical purposes, the nominal volume may be used to choose the balance.
If the standard uncertainty of measurement of the balance is known (e.g. from the balance calibration certificate), this
may be used instead of the repeatability and linearity. The standard uncertainty of measurement shall not be more
than two to three times the resolution.
4.2 Liquid reservoir, with sufficient capacity for all the test liquid likely to be required for the complete series of
tests.
4.3 Weighing vessel, suitable for the test procedure selected from clause 7. Care shall be taken regarding the loss
of water by evaporation during the dispensing and weighing procedure.
It is recommended that, especially for testing apparatus of the lowest volume, the height-to-diameter ratio of the
weighing vessel be at least 3:1 or that a weighing vessel with a lid be used.
4.4 Timing device, with a standard uncertainty of � 1s (see note to 4.7).
◦
4.5 Thermometer, with a standard uncertainty of � 0,2 C (see note to 4.7).
4.6 Hygrometer, with a standard uncertainty of � 10 % (see note to 4.7).
4.7 Barometer, with a standard uncertainty of � 0,5 kPa (see note to 4.7).
NOTE All uncertainties are specified using a coverage factor k of 1.
5 Test liquid
Use distilled or deionized water conforming grade 3 as specified in ISO 3696, degassed or air-equilibrated. The
water shall be at room temperature (see 6.2).
6 Test conditions
6.1 General
Apparatus that is routinely dismantled and reassembled within the scope of its intended use (e.g. for cleaning
purposes) shall be dismantled and reassembled at least once prior to the test in accordance with the supplier's
operation manual.
Apparatus shall be operated as specified in the supplier's operation manual.
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
6.2 Test room
The test shall be carried out in a draught-free room with a stable environment. The test room shall have a relative
◦ ◦ ◦
humidity above 50 % and a constant (± 0,5C1) temperature between 5C3 and 0 C. Prior to the test, the
apparatus to be tested and the test water shall have stood in the room for a sufficient time, at least 2h, to reach
equilibrium with the room conditions.
NOTE See 8.3 for corrections to be made when the balance readings are converted to volumes.
6.3 Evaporation
Especially for small volumes below 50µl, errors due to evaporation of the test liquid during weighing shall be taken
into consideration. Apart from the design of the weighing vessel (4.3), the test cycle time is important.
In order to keep the error due to evaporation as small as possible, the following additional items can be considered,
if volumes below 50µl are tested:
— a balance with appropriate accessories such as an evaporation trap could be used; or
— the test liquid to be weighed could be delivered into a capillary tube, although this method does not replicate the
normal method of use and the user should verify for himself that correlation exists.
Regardless of these items, the error due to evaporation during the measuring series can be determined
experimentally (see 7.2.8) and compensated mathematically (see 8.1). The uncertainty of this compensation should
be added to the uncertainty of measurement.
6.4 Test cycle time
The test cycle time (time required to complete the weighing of one dispensed volume) shall be kept to a minimum. It
should ideally not exceed 60 s. It is important that it is regular, both within each cycle and as far as possible from
cycle to cycle, so that a reliable mathematical compensation of the error due to evaporation during the measuring
series can be applied.
7 Procedure
7.1 General
7.1.1 Test volume
In the case of a fixed-volume apparatus, the test volume is the nominal volume. In the case of a variable-volume
(user-selectable volume) apparatus, at least three volumes shall be tested:
— the nominal volume,
— approximately 50 % of the nominal volume,
— the lower limit of the useful volume range or 10 % of the nominal volume (whichever is the greater).
Measurement of further volumes is optional. The setting devices of the apparatus (e.g. dials, scales) shall be
sufficient for the selection of the test volume.
7.1.2 Number of measurements per test volume
If the gravimetric methods of this part of ISO 8655 are used as conformity tests or type tests, e.g. prior to a
declaration or certification of conformity, or if the gravimetric method is used as a reference method,
10 measurements for each test volume shall be carried out. These measurements are used to calculate the
systematic and the random error of measurement in accordance with clause 8.
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
For re-establishing conformity, e.g. after repairs not performed by the supplier, 10 measurements at each volume
shall also be performed.
If the gravimetric method is used for other purposes, such as supplier's quality control or supplier's after-sales
service,
— the number of test volumes (see 7.1.1),
— the number of measurements per volume and,
— where applicable, the number of channels tested
may be changed to an appropriate number. Alternative test methods may also be used for this purpose, provided that
they can be proven to correlate with the reference method specified in this part of ISO 8655, in which case the user
should choose a number of measurements for his metrological confirmation based on his accuracy requirements.
7.1.3 Weighing procedure
Weighing for apparatus designed to deliver (Ex) shall always involve dispensing of the test liquid into the weighing
vessel. Weighing for apparatus designed to contain (In) shall always involve the removal of test liquid from the
weighing vessel. An example of the latter is the sample uptake step in the use of a dilutor.
7.1.4 Test conditions during the weighing procedure
At the start and at the end of the weighing procedure, the temperature of the test liquid in its container shall be
◦
recorded to the nearest 0,2 C. The barometric pressure in the test room shall be recorded to the nearest 1 kPa and
the relative humidity to the nearest 10 %.
7.2 Single-channel piston pipettes with air interface (in accordance with ISO 8655-2)
7.2.1 In the case of power-driven piston pipettes, aspiration and delivery of test liquid are automatic. The remainder
of the procedure is carried out following the procedure described below.
7.2.2 Place test liquid from the water container in the weighing vessel to a depth of at least 3mm. Record the
temperature of the test liquid and the barometric pressure and relative humidity in the test room (see 7.1.4). If the
weighing vessel has a lid, fit it.
NOTE Temperature and barometric pressure are necessary for the choice of the correction factor Z (see 8.3 and annex A); the
relative humidity is not necessary for the evaluation as the correction factors Z in annex A apply to relative humidities ranging from
20 % to 90 % but are necessary for documentation in the test report [see clause 9, item d)].
7.2.3 If using a variable-volume piston pipette, select the test volume; this setting shall not be altered during the test
cycle of 10 measurements.
7.2.4 Prepare the piston pipette and the test cycle as follows:
a) Fit the selected tip to the piston pipette.
b) Fill the tip with test liquid and expel to waste five times to reach a humidity equilibrium in the dead air volume (see
ISO 8655-1:2002, 3.1.8) of the air-displacement piston pipette.
c) Place the weighing vessel with its added water on the balance pan.
7.2.5 Perform the following test cycle (see Figure 1 and Figure 2):
a) Replace the disposable tip of the piston pipette.
b) Fill the piston pipette with test liquid, immersing its delivery orifice 2mm to 3mm below the surface of the water.
Release the operating button slowly, if hand operated, and withdraw the pipette vertically and carefully from the
surface of the water. Touch the delivery orifice against the side wall of the container with the test liquid.
c) Expel the water to waste in order to pre-wet the tip and refill the piston pipette as described in b).
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
d) Record the mass m of the weighing vessel to the nearest readable graduation as in Table 1, or tare the balance
0
to zero (m = 0). Start the timing device (this may be omitted if using a weighing vessel with lid).
0
e) If the weighing vessel has a lid, remove it. Deliver the contents of the pipette into the weighing vessel, touching
the delivery end of the pipette tip against the inside wall of the vessel just above the liquid surface at an angle of
◦ ◦
approximately 30 to 45 and draw it approximately 8mm to 10mm along the inner wall of the weighing vessel
to remove any droplets at or around the tip orifice. Replace the lid if applicable.
Where applicable, use the blow-out feature of the piston pipette to expel the last drop of liquid before drawing the
delivery end of the tip along the inner wall of the weighing vessel.
If it is necessary to remove the weighing vessel from the balance pan to permit delivery of the dispensed volume,
avoid excessive handling and possible contamination by the use of lint-free gloves. Return the weighing vessel to
the balance pan after delivery.
f) Record the mass m of the weighing vessel, or if tared in step 7.2.4 c) the mass m of the quantity delivered.
1 i
12345
Depress Immerse tip Release Withdraw tip
Wait 1sto 2s
plunger in water plunger from water
6789 10
Touch tip on Depress Wipe tip on Remove tip Release
the weighing plunger the weighing from the plunger
vessel vessel weighing
vessel
Figure 1 — Pipetting of testing volume into the weighing vessel
1234
Wet pipette tip Change tip Wet tip once Determine tare
five times mass
567
Pipette the Determine gross Further
test volume mass measurements,
starting at step 2
Figure 2 — Scheme of test procedure for piston pipettes with air interface
7.2.6 Repeat the test cycle described in 7.2.5 until 10 measurements have been recorded as a series of masses
m to m .
1 10
7.2.7 Note the time to the nearest second taken to complete the 10 test cycles.
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
7.2.8 After the last weighing of 7.2.6 leave the weighing vessel on the balance pan for the time measured in 7.2.7
and record its mass m .
11
If the weighing vessel was removed from the balance pan to enable delivery, leave it on the pan for half the time in
7.2.7 and then remove it from the balance and allow it to stand on the workbench for half the time measured in 7.2.7.
> 50µl
If the test volume is or if a weighing vessel with lid is used, omit steps 7.2.7 and 7.2.8, as a correction for
evaporation is unnecessary. At 50µl and below, calculate the mass loss in accordance with the supplier's
instructions.
◦
7.2.9 Measure the temperature of the remaining test liquid to the nearest 0,2 C and calculate and record the mean
test temperature (see 7.1.4).
7.2.10 The values obtained shall be evaluated in accordance with clause 8.
7.3 Multi-channel piston pipettes (in accordance with ISO 8655-2)
Multi-channel piston pipettes are similar to single-channel in that they comprise a set of single-volume measuring
and delivery units all operated simultaneously by a single operating mechanism. For the purposes of the test, each
channel shall be regarded as a single channel and tested and reported as such.
Fill all channels of the multi-channel pipette by aspirating the test liquid. Expel only the test liquid aspirated by the
channel being tested into the weighing vessel.
7.4 Positive-displacement pipettes (in accordance with ISO 8655-2)
Piston pipettes without an air interface shall be tested in accordance with 7.2. However, the five-fold prewetting of the
pipette tip prior to the test and the single prewetting before each measurement only need be performed if required by
the supplier. Only change the pipette tips when testing positive-displacement pipettes of type D2 (see ISO 8655-2).
Wipe the pipette tip on the water container wall after aspiration of the test liquid and prior to expelling it into the
weighing vessel in order to remove droplets from the outside of the tip. Without removing liquid from the inside of the
pipette tip, further remove any droplets that may still be present after the wiping of the tip. Follow the supplier's
instructions regarding air-bubble-free filling of the pipette tip.
Empty the contents of the pipette tip into the weighing vessel as specified in 7.2.5 e).
7.5 Piston burettes (in accordance with ISO 8655-3)
7.5.1 Preparation
Carry out the testing by delivery into the weighing vessel (see 7.1.3). Carefully clean the weighing vessel and add a
small quantity of test liquid to it. Place the weighing vessel and its test liquid in the balance case. Then place the
burette under test, with its reservoir already filled with test liquid, as close to the balance as possible. Leave both for
at least 2h to come to equilibrium.
7.5.2 Test procedure
Measure the mass of the weighing vessel and its test liquid and consider this value as the tare mass prior to the first
measurement.
Load the piston burette, bubble free, with test liquid from the reservoir, in accordance with the supplier's instructions.
Deliver the test liquid from the burette into the weighing vessel, until the selected volume is reached. If the burette is
automatically controlled, deliver test liquid until the volume preset is reached and no further delivery occurs. Weigh
the weighing vessel again and calculate the mass of liquid delivered.
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SIST EN ISO 8655-6:2002
ISO 8655-6:2002(E)
When testing partial volumes (see 7.1.1) of the nominal volume of the piston burette, the piston need not be reset to
the initial position (zero) prior to the next measurement. Ensure that the upper volume limit of the piston and thus the
nominal volume of the piston burette is not exceeded when dispensing a partial volume.
When testing piston burettes — especially in the case of automated tests — wiping of the delivery jet on the vessel
wall to remove droplets can be impossible due to the individual test setup. In such cases, ascertain that the weighing
is carried out only after a complete drop has been delivered from the delivery jet into the weighing vessel.
The test liquid can, for example, be expelled through an extended tip in such a
...