SIST EN ISO 15212-1:2000
(Main)Oscillation-type density meters - Part 1: Laboratory instruments (ISO 15212-1:1998)
Oscillation-type density meters - Part 1: Laboratory instruments (ISO 15212-1:1998)
The standard specifies metrological and other requirements for density meters of the oscillation type, which are used in laboratories for homogeneous fluid samples. A method for adjustment and calibration is given.
Dichtemeßgeräte nach dem Schwingerprinzip - Teil 1: Laborgeräte (ISO 15212-1:1998)
Dieser Teil von ISO 15212 legt meßtechnische und andere Anforderungen an Dichtemeßgeräte nach dem Schwingerprinzip fest, die in Laboratorien für alle Arten von homogenen fluiden Proben angewendet werden. Zusätzlich wird eine Methode zur Justierung und Kalibrierung der Laborgeräte beschrieben. Die Geräte können zur alleinigen Dichtemessung dienen oder Teil einer komplexeren Meßeinrichtung sein, welche die Bestimmung weiterer Meßgrößen in der Probe ermöglicht.
Densimetres a oscillations - Partie 1: Instruments de laboratoire (ISO 15212-1:1998)
La présente partie de l'ISO 15212 spécifie les exigences de métrologie et autres applicables aux densimètres à oscillations utilisés dans les laboratoires pour tous les types d'échantillons de fluides homogènes. En outre, elle présente une méthode d'ajustage et d'étalonnage des instruments de laboratoire. Ces instruments sont des éléments isolés ou font partie d'un équipement de mesure complexe fournissant d'autres paramètres d'essai sur l'échantillon. La présente partie de l'ISO 15212 ne décrit pas la méthode d'utilisation des densimètres dans le cas d'applications ou de produits particuliers, tels que les produits pétroliers ou les boissons; de telles méthodes d'utilisation peuvent être définies par des organismes tels que l'ISO ou des agences gouvernementales compétentes. La présente partie de l'ISO 15212 ne définit pas la spécification d'un instrument pour une application particulière quelconque. Pour obtenir ces informations, il convient de se référer à la norme traitant de la méthode d'utilisation. La présente partie de l'ISO 15212 est destinée aux fabricants de densimètres et aux organismes procédant aux essais et à la certification de conformité des densimètres. En outre, cette partie de l'ISO 15212 présente des recommandations pour l'ajustage et l'étalonnage des densimètres par l'utilisateur.
Denzimetri - oscilacijski tip - 1. del: Laboratorijski instrumenti (ISO 15212-1:1998)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 15212-1:2000
01-junij-2000
Denzimetri - oscilacijski tip - 1. del: Laboratorijski instrumenti (ISO 15212-1:1998)
Oscillation-type density meters - Part 1: Laboratory instruments (ISO 15212-1:1998)
Dichtemeßgeräte nach dem Schwingerprinzip - Teil 1: Laborgeräte (ISO 15212-1:1998)
Densimetres a oscillations - Partie 1: Instruments de laboratoire (ISO 15212-1:1998)
Ta slovenski standard je istoveten z: EN ISO 15212-1:1999
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 15212-1:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 15212-1:2000
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SIST EN ISO 15212-1:2000
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SIST EN ISO 15212-1:2000
INTERNATIONAL ISO
STANDARD 15212-1
First edition
1998-10-01
Oscillation-type density meters —
Part 1:
Laboratory instruments
Densimètres à oscillations —
Partie 1: Instruments de laboratoire
A
Reference number
ISO 15212-1:1998(E)
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SIST EN ISO 15212-1:2000
ISO 15212-1:1998(E)
Contents Page
1 Scope .1
2 Normative references .1
3 Definitions .2
4 Principle and functional units .2
4.1 Measuring principle.2
4.2 Functional units .2
5 Density sensor .3
5.1 Sensor material.3
5.2 Sensor design .3
6 Requirements and tests .4
6.1 Oscillation system .4
6.2 Temperature control and measurement.5
6.3 Displays .7
6.4 Auxiliary units and data transfer.7
6.5 Safety requirements .8
6.6 Electromagnetic compatibility.8
7 Adjustment .8
8 Calibration .8
8.1 Density reference liquids .8
8.2 Particular density reference liquids.9
8.3 Calibration requirements .9
8.4 Calibration procedure.9
© ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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ISO ISO 15212-1:1998(E)
9 Density meter accuracy . 10
10 Manual . 10
11 Marking . 11
Annex A (normative) Density and compressibility of pure water . 12
Annex B (normative) Density of moist air . 17
Annex C (informative) Bibliography . 20
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SIST EN ISO 15212-1:2000
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ISO 15212-1:1998(E) ISO
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.
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.
International Standard ISO 15212-1 was prepared by Technical Committee ISO/TC 48, Laboratory glassware and
related apparatus, Subcommittee SC 4, Density measuring instruments.
ISO 15212 consists of the following parts, under the general title Oscillation-type density meters:
Part 1: Laboratory instruments
Part 2: Process instruments for liquids
Annexes A and B form an integral part of this part of ISO 15212. Annex C is for information only.
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SIST EN ISO 15212-1:2000
©
INTERNATIONAL STANDARD ISO ISO 15212-1:1998(E)
Oscillation-type density meters —
Part 1:
Laboratory instruments
1 Scope
This part of ISO 15212 specifies metrological and other requirements for oscillation-type density meters which are used
in laboratories for all kinds of homogeneous fluid samples. In addition, a method for adjustment and calibration of
laboratory instruments is given. The instruments are either stand-alone units or part of more complex measuring
equipment supplying additional test parameters of the sample.
This part of ISO 15212 does not describe the method of use of density meters for particular applications or products
such as petroleum products or beverages. Such methods of use can be defined by relevant institutions such as ISO or
responsible government agencies.
This part of ISO 15212 does not define an instrument specification for any particular application. For this information
reference should be made to the relevant standard covering the method of use.
This part of ISO 15212 is addressed to manufacturers of density meters and to bodies testing and certifying the
conformity of density meters. In addition, this part of ISO 15212 gives recommendations for adjustment and calibration
of density meters by the user.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
ISO 15212. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of ISO 15212 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
ISO 3585:1998, Borosilicate glass 3.3 — Properties.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
IEC 61010-1:1990, Safety requirements for electrical equipment for measurement, control and laboratory use — Part 1:
General requirements.
IEC 61326-1:1997, Electrical equipment for measurement, control and laboratory use — EMC requirements — Part 1:
General requirements.
1)
IEC 61326-1:— , Amendment 1.
1) To be published.
1
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ISO 15212-1:1998(E)
3 Definitions
For the purposes of this part of ISO 15212, the following definitions apply.
NOTE The definitions and terms used are in agreement with the "International Vocabulary of Basic and General Terms in
Metrology".
3.1
adjustment (of a density meter)
operation of bringing the instrument to a state of performance suitable for its use, by setting or adjusting the density
instrument constants
NOTE By adjustment, systematic measuring deviations are removed to an extent which is necessary for the provided
application. Adjustment demands an intervention which permanently modifies the instrument.
3.2
calibration (of a density meter)
set of operations that establishes the relationship between the reference density of standards and the
corresponding density reading of the instrument
NOTE By calibration, no intervention is made which permanently modifies, for example, the instrument constants set
during the adjustment procedure.
3.3
parasitic resonant points (of a density meter)
those oscillation frequencies at which the natural frequency of the density sensor is affected by oscillations of the
"counter mass", comprising the rest of the instrument
4 Principle and functional units
4.1 Measuring principle
The sensors used in density meters are electrically or mechanically induced oscillating systems, whose oscillation
frequencies or periods are a function of the sample density. Depending on the sensor design, the sensor can either
contain the fluid sample or be immersed in it. Instrument constants of the adjusted density meter are used to calculate
the sample density from the oscillation frequency or oscillation period.
4.2 Functional units
Oscillation-type density meters shall consist of the following functional units:
a) a density sensor capable of either being filled with the sample or of being immersed in it;
b) a device to excite and control sensor oscillation;
c) a device to determine and display the density and the oscillation frequency or period;
d) a device to determine and display the sample temperature for which the measured density is valid;
e) a system to detect and display malfunctions and operator errors.
The functional units a) to c) are designated as the oscillation system. In addition, oscillation-type density meters can
incorporate the following functional units:
f) a unit for controlling the temperature of the sample and density sensor;
g) sampling devices;
h) sensor cleaning devices.
All functional units a) to h) can be integrated into a single instrument or can be separate units.
2
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Key
A Density sensor (4.2a) D Temperature measurement (4.2d)
B Excitation transmitter (4.2b) E Functional monitoring (4.2e)
C Signal evaluation (4.2c)
Figure 1 — Functional units of a density meter
5 Density sensor
5.1 Sensor material
Density sensor materials can be, for example, borosilicate glass 3.3 in accordance with ISO 3585, metal, metal alloys
or plastics. The material is considered to be suitable if it shows in resistance tables the highest class of resistance
against the samples to be measured and the cleaning agents to be used in the density meter. Erosion as well as
special forms of corrosion shall be considered in this respect. Where there is no literature or practical data available,
the resistance of the sensor material should be tested as follows.
a) Weigh a clean and dry test piece identical to the sensor material. The maximum permissible error of the
balance shall not exceed 0,01 % of the test-piece mass.
b) Immerse the test piece in the fluid to be measured with the sensor, under the intended measuring conditions,
e.g. temperature and pressure.
c) After 12 h remove, clean, dry and weigh the test piece.
The sensor material is considered to be resistant if the mass of the test piece is changed by the test procedure by
less than + 0,05 %.
5.2 Sensor design
Density sensors can be designed as straight, U-formed or omega-formed tubes. Other designs are tuning-forks,
cylinders, bells or membranes. All designs which conform to the functional principle in accordance with 4.1 can be
constructed.
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ISO 15212-1:1998(E)
6 Requirements and tests
All the tests of clause 6 are intended to be type tests.
6.1 Oscillation system
6.1.1 Drift
6.1.1.1 Within 24 h, the drift of the displayed density Δρ at a constant temperature of 20 °C shall not exceed 1 %
24
of the maximum permissible error specified by the manufacturer of the instrument.
If the density meter is not designed for a measuring temperature of 20 °C, the drift at the mean measuring temperature
of the density meter shall not exceed 5 % of the specified maximum permissible error.
6.1.1.2 Switch on the instrument and allow the temperature to equilibrate for 24 h.
Adjust the instrument (see clause 7) in accordance with the manufacturer's instructions.
Fill the instrument three times and measure the density of water of Grade 2 in accordance with ISO 3696 at
(20 + 0,1) °C. Record the mean value of the threefold measurement ρ .
1
Repeat the measurement (without a new adjustment) and repeat the mean value calculation ρ after a minimum of
2
10 days. The instrument and thermostating device shall be in operation during the whole test procedure.
To calculate the drift, use the following equation:
rr-
21
Dr =
24
Dt
where Δt is the difference in days between the two threefold measurements.
If the density meter is not designed for a measuring temperature of 20 °C, testing shall be performed at the mean
measuring temperature of the density meter.
6.1.2 Effect of sample viscosity
6.1.2.1 The oscillation system shall be constructed in such a way that the maximum permissible errors conform to
the requirements of clause 9 when measuring samples of different viscosities and, where appropriate, with different
sound velocities.
6.1.2.2 Use Newtonian liquids of known densities and viscosities as well as, where appropriate, known densities and
sound velocities which suit the intended application of the density meter. The liquids shall be non-corrosive to the
materials of the density sensor. Testing shall be performed in accordance with clause 9.
6.1.3 Deviation between sample and sensor temperatures
6.1.3.1 The oscillation system shall be constructed and built in such a way that the deviation between sample
temperature and sensor temperature at the moment of display of the result does not exceed the values given in 6.2.
Check the displayed density of the instrument over a defined time period. For this
6.1.3.2
switch on the instrument and set the measurement temperature to 20 °C;
attemperate the instrument for 24 h;
precondition to 30 °C a reference liquid with high thermal density dependency;
fill the density sensor with the preconditioned reference liquid.
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ISO 15212-1:1998(E)
The first density value displayed by the instrument as valid or read from the instrument after a time period specified by
the manufacturer is compared with the density value displayed after 10 min. The difference between the two values
shall not exceed 20 % of the maximum permissible error specified for the density meter by the manufacturer.
NOTE Bromobenzene or n-nonane are suitable examples of reference liquids for this test.
Warning: Bromobenzene is a hazardous substance and may not be permitted under Safety Regulations.
If the density meter is not designed for a measuring temperature of 20 °C, testing shall be performed at the mean
measuring temperature of the density meter.
6.1.4 Effect of oscillations
6.1.4.1 Measurement deviations arising from the effect of oscillations of instrument parts on the density sensor shall
not exceed 20 % of the maximum permissible error, specified for the density meter by the manufacturer, over the whole
measuring range.
6.1.4.2 Examine the oscillatory characteristics of the built-in density sensor provided by the manufacturer. This test
may not show, over the whole density measurement range, any parasitic resonant points (see 3.3) whose effects
exceed 20 % of the maximum permissible error specified for the density meter by the manufacturer.
6.2 Temperature control and measurement
6.2.1 Requirement
The temperature sensor shall be built-in or a separate temperature unit shall be fitted in such a way that good thermal
contact with the sample is guaranteed. The deviation between the displayed and actual sample temperatures shall not
–1 3
be greater than the maximum permissible error of the density meter multiplied by the factor 0,2 °C�kg �m .
–3 –1
NOTE For the definition of this factor, an extreme thermal density deviation of 2,4 kg�m {K has been assumed.
If the application range of the density meter is limited to aqueous samples and water-containing mixtures, the factor to
–1 3
be multiplied by the maximum permissible error can be increased to 0,5 °C�kg �m .
6.2.2 Test conditions
The measurement of the temperature deviation between displayed and actual sample temperatures shall be performed
by direct temperature measurement inside the density sensor or by indirect measurement.
The indirect test shall be performed by adjustment of the instrument (see clause 7), followed by calibration (see 8.4) of
the density meter with two reference liquids, specially selected for this test (see 8.2), at the following test temperatures:
at 20 °C;
at a temperature near the lower limit of the temperature measurement range of the density meter; and
at a temperature near the upper limit of the temperature measurement range.
If the density meter is not designed for the measurement temperature of 20 °C, the test shall be performed at the mean
measurement temperature of the instrument.
The density values of the reference liquids, selected for this test (see 8.2), shall not exceed a density difference of
–3
300 kg�m ; the reference liquids shall have a different thermal density dependency dr/dq.
6.2.3 Test procedure
Clean the density sensor and switch on the instrument according to the manufacturer's instructions.
Attemperate the sensor at (20 – 0,1) °C for 24 h.
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Adjust (see clause 7) the instrument according to the manufacturer's instructions.
Calibrate the instrument according to 8.4 using the first selected reference liquid according to 8.2. Record the error
of measurement Dr .
3
Calibrate the instrument using the second selected reference liquid. Record Dr .
4
NOTE If the instrument has been adjusted (see clause 7) with water according to Grade 2 of ISO 3696, and if the
reference liquid (see 8.2) for the first calibration is different from water, this second calibration may be omitted.
Repeat the test procedure at the two other temperatures.
6.2.4 Evaluation of the test
Calculate the viscosity correction C for the viscosity and density of the first reference liquid at the three
h r
rh()
33 3 3
test temperatures according to the manufacturer's instructions. Subtract the viscosity correction from the recorded
error of measurement Dr :
3
CCr=-Dr
3 rh
3 ()
33
Perform the same calculation for the second reference liquid:
CC=-Dr
r 4 rh
4 ()
44
Calculate the proximity value for the deviation between the indicated temperature and the actual sample
D
q
temperature in the density sensor at each of the three test temperatures according to the equation:
CC-
rr
43
D = 07, 5·
q
()ddrq//-(dr dq)
34
where
dr /dq is the thermal density dependency of the first reference liquid;
3
dr /dq is the thermal density dependency of the second reference liquid.
4
NOTE 1 The correction factor 0,75 assumes that 25 % of the measurement deviations are not due to temperature deviations.
None of the three calculated proximity values D shall exceed the maximum permissible error of the instrument
q
3 –1 3 –1
multiplied by the factor 0,2 °C�m �kg or 0,5 °C�m �kg .
NOTE 2 If the instrument has been adjusted with water according to Grade 2 of ISO 3696 and the second calibration has
been omitted, the term C can be cancelled in the last equation and dr /dq equals the thermal density dependency of water,
r 4
4
calculated from the values given in table A.1 of annex A. Under these circumstances, n-nonane or n-dodecane are well suited
reference liquids for this test. The thermal density dependencies are as follows:
–3 –1
dr /dq = -0,78 kg�m �°C
non
–3 –1
dr /dq = -0,73 kg�m �°C
dod
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6.3 Displays
6.3.1 Display of results
The displays shall be designed in such a way that
3 3
the density is displayed in kg/m or g/cm together with the measurement unit;
the resolution of the density display on a digital scale corresponds to table 1;
the scale interval on an analog scale is equal to the maximum permissible error (see table 1) and the spacing
of the scale marks is 1 mm minimum.
Table 1 — Resolution and maximum permissible errors
Maximum permissible
Resolution Factor
error
3 3
kg/m kg/m
1,0 0,1 1/10
0,5 0,1 1/5
0,20 0,01 1/20
0,10 0,01 1/10
0,05 0,01 1/5
Density instruments for special applications (e.g. scientific research) may have a resolution of the density display of
3 3 3
0,001 kg/m or 0,000 001 g/cm , if the specified maximum permissible error does not exceed 0,1 kg/m or
3
0,0001 g/cm and if the least significant digit is unambigously marked (e.g. by distinction in size or colour).
6.3.2 Additional displays
The displays shall be designed in such a way that
the oscillation period or frequency is displayed on request and is clearly distinguished from the density display;
the temperature of the liquid is displayed in degrees Celsius;
the measurement unit is displayed together with the measurement value;
the malfunctions are displayed;
the instrument constants are displayed on request.
Additional instrument data, if available, may be displayed on request.
With a battery-powered density meter, the displayed values shall be clearly recognized as invalid if the lower or upper
limit of the operating voltage is exceeded.
A visual check shall be carried out to ensure that the resolution of the density display complies with the
manufacturer's specification in accordance with clause 9.
6.4 Auxiliary units and data transfer
If the density meter consists of several separated units or if additional devices are connected, the data shall be
transferred unchanged and unaffected.
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Additional devices for showing measured data shall display those unchanged and unaffected.
The interfaces, data transfer and additional units shall be clearly defined and shall work without susceptibility to
interferences, i.e. they shall not influence the data nor cause any malfunctions.
If the interfaces, data transfer and additional units differ from these definitions or are faulty, the display of the
measured data shall be clearly recognized as invalid.
6.5 Safety requirements
The safety requirements according to IEC 61010-1 shall be followed, as far as they are applicable to oscillation-type
density meters.
Testing shall be in accordance with IEC 61010-1.
6.6 Electromagnetic compatibility
The EMC requirements specified in IEC 61326-1 and its amendment shall be followed as far as they are applicable to
oscillation-type density meters.
Testing shall be in accordance with the above-mentioned standards.
7 Adjustment
The density meters shall be adjusted according to the manufacturer's instructions. Adjustment is performed by
determining and setting of the instrument constants (see clause 3). At least the last 50 sets of constants shall be
permanently stored automatically in the density meter.
Normally, adjustment can be performed with air and water of Grade 2 in accordance with ISO 3696, and should be
performed at the intended measurement temperature. The density values of water are specified in table A.1 and the
density values of moist air are specified in table B.1.
After each maintenance of the instrument, an adjustment of the density meter shall be performed.
8 Calibration
8.1 Density reference liquids
For testing and calibrating density meters in accordance with this part of ISO 15212, reference liquids shall be used
whose density values and, if required, viscosities and sound velocities are known within the intended working range of
temperature, pressure and flow.
The density values of the reference liquids shall be determined in a manner traceable to national standards. They shall
have a certified uncertainty at the 95 % confidence level ( = 2) that is not greater than 30 % of the maximum
k
permissible error of the density meter to be tested.
If water of Grade 2 in accordance with ISO 3696 is used as a test or reference liquid, the quality of this water shall be
regularly checked and documented. The density values of water listed in table A.1 of annex A shall be applied.
The electrical conductivity of water should preferably be used for quality control. The conductivity of freshly prepared
–1
water (Grade 1 in accordance with ISO 3696) should not exceed 0,01 mS�m .
The reference liquids shall be selected with regard to the use of the density meter, i.e. their properties shall meet
the application of the instrument.
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8.2 Particular density reference liquids
The density values of reference liquids, used for testing of temperature control and measuring (see 6.2), shall be
certified at the 95 % confidence level (k = 2) as function of their thermal density dependency:
–3 –1 –3
— up to 1,0 kg m �K with an uncertainty of 0,01 kg m ,
� �
–3 –1 –3
— from 1,0 to 1,7 kg�m �K with an uncertainty of 0,02 kg�m ,
–3 –1 –3
— from more than 1,7 kg�m �K with an uncertainty of 0,03 kg�m .
The thermal temperature dependency shall be certified at the 95 % confidence level (k = 2) with an uncertainty not
exceeding 10 % of the thermal density dependency. The viscosities of these reference liquids shall be known and
shall not exceed 5 mPa�s.
8.3 Calibration requirements
For validation of the density meter accuracy, e.g. according to clause 9, calibration shall be performed by measurement
of the density of the the density reference liquids (see 8.1) with known densities and, if required, known viscosities and
sound velocities. The density indicated by the instrument is compared with the appropriate certified densities of these
reference liquids.
Calibration shall be performed within the density measuring range and within the working ranges of temperature and
viscosity and, where appropriate, pressure, flow and sound velocity, which are suitable for the density meter.
Calibration points shall be selected which lie close to the lower and upper limit and in the middle of the respective
density measuring range. The positions of the calibration points depend upon the selected reference liquids as well as
upon
...
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