ISO 19685:2017

INTERNATIONAL ISO
STANDARD 19685
First edition
2017-09
Vacuum technology — Vacuum
gauges — Specifications, calibration
and measurement uncertainties for
Pirani gauges
Technique du vide — Manomètres à vide — Spécifications, étalonnage
et incertitudes de mesure pour les jauges Pirani
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 4
5 Principle of Pirani gauge . 4
6 Specifications for Pirani gauge . 5
6.1 General . 5
6.2 Measuring principle . 5
6.3 Type of output . 5
6.4 Range of output and output display resolution . 5
6.5 Measurement range and full scale . 5
6.6 Expected measurement uncertainty . 5
6.7 Material exposed to gas . 5
6.8 Connecting flange . 5
6.9 Interface and pin-connections . 6
6.10 Warm-up period . 6
6.11 Compatibility between gauge tube and controller . 6
6.12 Normal operating (environment) conditions . 6
6.13 Electrical power supply . 6
6.14 Cable length . 6
6.15 Maximum bake-out temperature . 6
6.16 Dimensions of gauge head and controller . 6
6.17 Mounting orientation . 6
7 Additional (optional) specifications for Pirani gauge . 6
7.1 Long-term instability . 6
7.2 Relative sensitivity factor . 7
7.3 Hysteresis . 7
7.4 Response time. 7
7.5 Inspection record and calibration certificate . 7
7.6 Configuration . 7
7.7 Weight . 7
7.8 Storage and transport condition . 7
7.9 Photographs . 7
7.10 Maximum power consumption . 7
7.11 Set point of pressure . 7
8 Calibration and other measurement procedures. 7
8.1 General . 7
8.2 Conditions for calibrations . 8
8.3 Assembly and adjustments of calibration item . 8
8.4 Calibration . 9
8.5 Measurement uncertainties during calibration . 9
8.6 Calibration certificate . 9
8.7 Measurement procedure for hysteresis .10
8.8 Measurement procedure of response time.10
9 Measurement uncertainties at use .10
Annex A (informative) Typical Pirani gauge .12
Bibliography .13
Foreword
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This document was prepared by Technical Committee ISO/TC 112, Vacuum technology.
iv © ISO 2017 – All rights reserved

Introduction
ISO 3567 and ISO 27893 are basic standards with no specific guidelines of a special type of vacuum
gauge and are generally applicable. Detailed guidance for a specific gauge is intended to be given in
separate technical specifications for the calibration of special types of gauges.
This document complements ISO 3567 and ISO 27893 when characterizing or calibrating Pirani gauges
or using them as reference gauges.
Pirani gauges are widely used to measure pressures in the medium vacuum up to atmospheric pressure.
The relevant parameters, calibration guidelines and uncertainties for the dissemination of the pressure
scale and measurement of low and medium vacuum pressures by a Pirani gauge are described in this
document.
INTERNATIONAL STANDARD ISO 19685:2017(E)
Vacuum technology — Vacuum gauges — Specifications,
calibration and measurement uncertainties for Pirani
gauges
1 Scope
This document identifies parameters of Pirani gauges, their calibration procedure, and describes
measurement uncertainties to be considered when operating these gauges.
This document applies to Pirani vacuum gauges operating over a pressure range of 0,01 Pa to 150 kPa.
This document complements ISO 3567 and ISO 27893 when calibrating Pirani gauges and using them as
reference standards.
In addition, this document defines procedures to characterize Pirani gauges for response time and
hysteresis.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3567:2011, Vacuum gauges — Calibration by direct comparison with a reference gauge
ISO 27893, Vacuum technology — Vacuum gauges — Evaluation of the uncertainties of results of
calibrations by direct comparison with a reference gauge
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and d
...