ISO/TR 18931:2001
(Main)Imaging materials - Recommendations for humidity measurement and control
Imaging materials - Recommendations for humidity measurement and control
This Technical Report discusses devices in photographic standardization that are used as hygrometers and humidistats in the measurement and control of relative humidity (RH) in test chambers and storage areas. Special attention is given to situations where a photographic standard specifies controlling relative humidity to _ 2 % RH or better. Electric hygrometers are recommended for their precision, low cost, and accuracy when properly calibrated. Calibration can be done either by the vendor or in-house by a dew-point measurement. Where the budget permits, dew-point combined with ambient temperature measurements (converted to relative humidity) may be the only sensor system.
Matériaux pour l'image — Recommandations pour le mesurage et le contrôle de l'humidité
Upodobitveni materiali - Priporočila za merjenje in nadzor vlažnosti
Obravnava naprave pri fotografski standardizaciji, ki se uporabljajo kot higrometri in humidistati pri merjenju in nadzoru relativne vlažnosti v preskusnih komorah in prostorih za shranjevanje.
General Information
Buy Standard
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 18931
First edition
2001-06-01
Imaging materials — Recommendations for
humidity measurement and control
Matériaux pour l'image — Recommandations pour le mesurage et le
contrôle de l'humidité
Reference number
ISO/TR 18931:2001(E)
©
ISO 2001
---------------------- Page: 1 ----------------------
ISO/TR 18931:2001(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2001
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 either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2001 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 18931:2001(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Terms and definitions .1
3 Moisture content of gases .2
4 Measuring systems .2
5 Sensor location.5
6 Recommendations.5
Annex A Importance of relative humidity.6
Annex B Humidity control in storage areas.7
Bibliography.8
© ISO 2001 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/TR 18931:2001(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 thorugh 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.
The main task of technical committees is to prepare International Standards. 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 seventy-five percent of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that which is
normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority
vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature
and does not have to be reviewed until the data it provides are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this Technical Report may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 18931 was prepared by Technical Committee ISO/TC 42, Photography.
iv © ISO 2001 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TR 18931:2001(E)
Introduction
Some tests in photographic International Standards are carried out at a specified temperature and relative humidity
o o
(RH). A typical test condition is 23 C� 1 C and (50� 2) % RH.
o
Temperature is relatively easy to measure and control to within � 1 C. Accurate thermometers of several types,
which have been calibrated by a national standards laboratory or by the vendor and traceable to a standards
laboratory, are readily available.
Humidity is much more complex. Calibration by national standards laboratories can be expensive, and the relatively
long turn-around time conflicts with the need for frequent recalibration of the most useful humidity sensors. Some
instrument vendors are now providing calibration traceable to the National Institute of Standards and Technology
(NIST) at moderate cost. In other situations, the standards user may wish to do his own calibration. It should be
noted that calibration is complicated by the lack of useful reference points; relative humidities of 0 % and 100 %, for
example, are not readily measurable. The accurate and precise determination of relative humidity is usually done
indirectly and the results converted to relative humidity.
This Technical Report discussed devices used as hygrometers and humidistats in the measurement and control of
relative humidity. The importance of relative humidity as opposed to other moisture parameters is discussed in
annex A.
© ISO 2001 – All rights reserved v
---------------------- Page: 5 ----------------------
TECHNICAL REPORT ISO/TR 18931:2001(E)
Imaging materials — Recommendations for humidity measurement
and control
1 Scope
This Technical Report discusses devices in photographic standardization that are used as hygrometers and
humidistats in the measurement and control of relative humidity (RH) in test chambers and storage areas. Special
attention is given to situations where a photographic standard specifies controlling relative humidity to �2%RH or
better.
Electric hygrometers are recommended for their precision, low cost, and accuracy when properly calibrated.
Calibration can be done either by the vendor or in-house by a dew-point measurement. Where the budget permits,
dew-point combined with ambient temperature measurements (converted to relative humidity) may be the only
sensor system.
2 Terms and definitions
For the purposes of this Technical Report, the following terms and definitions apply.
2.1
absolute humidity
mass of water vapour per unit volume of wet gas
NOTE It is a measure of the amount of water present as part of the chemical analysis of the space, i.e., how much water is
availble for chemical activity.
2.2
accuracy
degree of conformity of a measurement to an accepted standard or ideal (true) value
2.3
desiccant
drying agent
2.4
dew-point
temperature to which moisture-laden air must be cooled to induce condensation
2.5
dry-bulb temperature
true temperature of the air at rest, i.e., the temperature as measured with ordinary instrumentation
2.6
frost-point
temperature to which moisture-laden air must be cooled for frost or ice formation
2.7
humidistat
device that senses the moisture content of the air for the purpose of controlling it
© ISO 2001 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO/TR 18931:2001(E)
2.8
humidity
general term for the amount of water vapour in the air
2.9
hygrometer
instrument that measures the moisture content of an air specimen
2.10
mixing ratio
mass of water vapour per unit mass of dry air
2.11
mole ratio
number of moles of water vapour per mole of dry gas
2.12
percent saturation
mass of water vapour present relative to the mass at saturation
NOTE Oftenconfusedwithrelativehumidity.
2.13
precision
measure of repeatability; the degree of closeness of a series of measurements under the same operating
conditions
2.14
relative humidity
ratio, expressed as a percentage, of the existing partial vapour pressure of water to the vapour pressure at
saturation
2.15
wet-bulb temperature
temperature indicated by a temperature sensor covered by a wetted wick
3 Moisture content of gases
The moisture content of a gas specimen can be expressed in a variety of ways. Details are given in the literature
(see [1] in the bibliography) and are beyond the scope of this Technical Report. Some methods have been defined
above and include absolute humidity, relative humidity, dew-point, etc. They are interrelated, and each has its place
with scientists, engineers, meteorologists, etc.
Films and papers respond directly to relative humidity, and this justifies its specification in International Standards
concerning photography (see annex A).
4 Measuring systems
Humidity devices serve one or more of the following purposes:
� measurement;
� control;
� calibration.
2 © ISO 2001 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/TR 18931:2001(E)
Of the more than ten fundamentally different ways to measure moisture content (see [2], [3], [4] in the bibliography),
only the most significant for International Standards concerning photography will be discussed. Applicability to each
of the above purposes will be included.
Agreement among laboratories to within � 2 % RH is obviously not possible with instrument accuracies of only
� 5 %. This Technical Report will, therefore, stress accuracy.
4.1 Gravimetric train (calibration only)
In this method, technicians weigh a small amount of a powerful drying agent. A moist air specimen is then passed
through so as to remove all its moisture. The drying agent is then reweighed. Equilibrium moisture content is
achieved when a repeat measurement at a greater time interval shows no change. The difference in weight
determines the moisture content.
Although simple in principle, the procedure is complex in practice and a single measurement can take hours, days
or weeks to perform. The apparatus fills a room and is used by national standards laboratories to provide the
ultimate standard of accuracy.
4.2 Dew-point/Frost-point hygrometers; also called condensation hygrometers (secondary
calibration, measurement and control)
This is the most accurate off-the-shelf method to calibrate working humidity sensors. Dew-point is the temperature
at which moisture from the carrier gas condenses on a chilled surface. When the ambient temperature is also
measured, relative humidity can be calculated either off-line or by an internal microprocessor. Commercial
instruments use a mirror chilled by a thermoelectric cooler together with a light-emitting diode and a photocell which
receives the reflected image. Moisture condensation causes the light to scatter, at which point the feedback circuit
from the photocell controls the cooling so as to maintain the mirror temperature at t
...
SLOVENSKI STANDARD
SIST-TP ISO/TR 18931:2011
01-julij-2011
8SRGRELWYHQLPDWHULDOL3ULSRURþLOD]DPHUMHQMHLQQDG]RUYODåQRVWL
Imaging materials - Recommendations for humidity measurement and control
Matériaux pour l'image -- Recommandations pour le mesurage et le contrôle de
l'humidité
Ta slovenski standard je istoveten z: ISO/TR 18931:2001
ICS:
37.040.20 )RWRJUDIVNLSDSLUILOPLLQ Photographic paper, films
IRWRJUDIVNHSORãþH)LOPVNL and cartridges
]YLWNL
SIST-TP ISO/TR 18931:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST-TP ISO/TR 18931:2011
---------------------- Page: 2 ----------------------
SIST-TP ISO/TR 18931:2011
TECHNICAL ISO/TR
REPORT 18931
First edition
2001-06-01
Imaging materials — Recommendations for
humidity measurement and control
Matériaux pour l'image — Recommandations pour le mesurage et le
contrôle de l'humidité
Reference number
ISO/TR 18931:2001(E)
©
ISO 2001
---------------------- Page: 3 ----------------------
SIST-TP ISO/TR 18931:2011
ISO/TR 18931:2001(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2001
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 either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2001 – All rights reserved
---------------------- Page: 4 ----------------------
SIST-TP ISO/TR 18931:2011
ISO/TR 18931:2001(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Terms and definitions .1
3 Moisture content of gases .2
4 Measuring systems .2
5 Sensor location.5
6 Recommendations.5
Annex A Importance of relative humidity.6
Annex B Humidity control in storage areas.7
Bibliography.8
© ISO 2001 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST-TP ISO/TR 18931:2011
ISO/TR 18931:2001(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 thorugh 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.
The main task of technical committees is to prepare International Standards. 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 seventy-five percent of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that which is
normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority
vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature
and does not have to be reviewed until the data it provides are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this Technical Report may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 18931 was prepared by Technical Committee ISO/TC 42, Photography.
iv © ISO 2001 – All rights reserved
---------------------- Page: 6 ----------------------
SIST-TP ISO/TR 18931:2011
ISO/TR 18931:2001(E)
Introduction
Some tests in photographic International Standards are carried out at a specified temperature and relative humidity
o o
(RH). A typical test condition is 23 C� 1 C and (50� 2) % RH.
o
Temperature is relatively easy to measure and control to within � 1 C. Accurate thermometers of several types,
which have been calibrated by a national standards laboratory or by the vendor and traceable to a standards
laboratory, are readily available.
Humidity is much more complex. Calibration by national standards laboratories can be expensive, and the relatively
long turn-around time conflicts with the need for frequent recalibration of the most useful humidity sensors. Some
instrument vendors are now providing calibration traceable to the National Institute of Standards and Technology
(NIST) at moderate cost. In other situations, the standards user may wish to do his own calibration. It should be
noted that calibration is complicated by the lack of useful reference points; relative humidities of 0 % and 100 %, for
example, are not readily measurable. The accurate and precise determination of relative humidity is usually done
indirectly and the results converted to relative humidity.
This Technical Report discussed devices used as hygrometers and humidistats in the measurement and control of
relative humidity. The importance of relative humidity as opposed to other moisture parameters is discussed in
annex A.
© ISO 2001 – All rights reserved v
---------------------- Page: 7 ----------------------
SIST-TP ISO/TR 18931:2011
---------------------- Page: 8 ----------------------
SIST-TP ISO/TR 18931:2011
TECHNICAL REPORT ISO/TR 18931:2001(E)
Imaging materials — Recommendations for humidity measurement
and control
1 Scope
This Technical Report discusses devices in photographic standardization that are used as hygrometers and
humidistats in the measurement and control of relative humidity (RH) in test chambers and storage areas. Special
attention is given to situations where a photographic standard specifies controlling relative humidity to �2%RH or
better.
Electric hygrometers are recommended for their precision, low cost, and accuracy when properly calibrated.
Calibration can be done either by the vendor or in-house by a dew-point measurement. Where the budget permits,
dew-point combined with ambient temperature measurements (converted to relative humidity) may be the only
sensor system.
2 Terms and definitions
For the purposes of this Technical Report, the following terms and definitions apply.
2.1
absolute humidity
mass of water vapour per unit volume of wet gas
NOTE It is a measure of the amount of water present as part of the chemical analysis of the space, i.e., how much water is
availble for chemical activity.
2.2
accuracy
degree of conformity of a measurement to an accepted standard or ideal (true) value
2.3
desiccant
drying agent
2.4
dew-point
temperature to which moisture-laden air must be cooled to induce condensation
2.5
dry-bulb temperature
true temperature of the air at rest, i.e., the temperature as measured with ordinary instrumentation
2.6
frost-point
temperature to which moisture-laden air must be cooled for frost or ice formation
2.7
humidistat
device that senses the moisture content of the air for the purpose of controlling it
© ISO 2001 – All rights reserved 1
---------------------- Page: 9 ----------------------
SIST-TP ISO/TR 18931:2011
ISO/TR 18931:2001(E)
2.8
humidity
general term for the amount of water vapour in the air
2.9
hygrometer
instrument that measures the moisture content of an air specimen
2.10
mixing ratio
mass of water vapour per unit mass of dry air
2.11
mole ratio
number of moles of water vapour per mole of dry gas
2.12
percent saturation
mass of water vapour present relative to the mass at saturation
NOTE Oftenconfusedwithrelativehumidity.
2.13
precision
measure of repeatability; the degree of closeness of a series of measurements under the same operating
conditions
2.14
relative humidity
ratio, expressed as a percentage, of the existing partial vapour pressure of water to the vapour pressure at
saturation
2.15
wet-bulb temperature
temperature indicated by a temperature sensor covered by a wetted wick
3 Moisture content of gases
The moisture content of a gas specimen can be expressed in a variety of ways. Details are given in the literature
(see [1] in the bibliography) and are beyond the scope of this Technical Report. Some methods have been defined
above and include absolute humidity, relative humidity, dew-point, etc. They are interrelated, and each has its place
with scientists, engineers, meteorologists, etc.
Films and papers respond directly to relative humidity, and this justifies its specification in International Standards
concerning photography (see annex A).
4 Measuring systems
Humidity devices serve one or more of the following purposes:
� measurement;
� control;
� calibration.
2 © ISO 2001 – All rights reserved
---------------------- Page: 10 ----------------------
SIST-TP ISO/TR 18931:2011
ISO/TR 18931:2001(E)
Of the more than ten fundamentally different ways to measure moisture content (see [2], [3], [4] in the bibliography),
only the most significant for International Standards concerning photography will be discussed. Applicability to each
of the above purposes will be included.
Agreement among laboratories to within � 2 % RH is obviously not possible with instrument accuracies of only
� 5 %. This Technical Report will, therefore, stress accuracy.
4.1 Gravimetric train (calibration only)
In this method, technicians weigh a small amount of a powerful drying agent. A moist air specimen is then passed
through so as to remove all its moisture. The drying agent is then reweighed. Equilibrium moisture content is
achieved when a repeat measurement at a greater time interval shows no change. The difference in weight
determines the moisture content.
Although simple in principle, the procedure is complex in practice and a single measurement can take hours, days
or weeks to perform. The apparatus fills a room and is used by national standards laboratories to provide the
ultimate standard of accuracy.
4.2 Dew-point/Frost-point hygrometers; also called condensation hygrometers (secondary
calibration, measurement and control)
This is the most accurate off-the-shelf method to calibrate working humidity sensors. Dew-point is the temperature
at w
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.