ISO 26142:2010 水素検出装置—固定アプリケーション | ページ 6

3.1

alarm set point

fixed or adjustable setting of the hydrogen detection apparatus that is intended to select the hydrogen volume fraction at which an indication, an alarm or another output function will automatically be activated

3.2

ambient air

normal atmosphere surrounding the hydrogen detection apparatus

3.3

aspirated hydrogen detection apparatus

hydrogen detection apparatus that samples the gas to be detected by introducing it to the hydrogen sensor(s) in a forced manner (e.g. use of a gas sampling pump or induction of a flow through a pressure differential)

3.4

clean air

air that is free of flammable gases, interfering or contaminating substances, and dust

3.5

control unit

part of hydrogen detection apparatus that is commonly referred to as the apparatus body and which excludes its remote sensor(s) and connections, if any

3.6

data collecting interval

time interval between the time when an indication data is collected and the time when the next indication data is corrected

3.7

diffusion chamber

chamber that can be sealed with controlled conditions of temperature, humidity and test-gas volume fraction, used for performing the test on the hydrogen detection apparatus

3.8

fault signal

audible, visible or other type of signal different from the alarm signal, providing, directly or indirectly, a warning or an indication that the hydrogen detection apparatus is not working satisfactorily

3.9

final indication

indication given by the hydrogen detection apparatus after stabilization

3.10

hydrogen detection apparatus

assembly with an integrated or a remote hydrogen sensor that is intended to detect and measure the hydrogen volume fraction over a declared measuring range

Note 1 to entry: The hydrogen detection apparatus may be provided with a single or multiple alarm set points.

Note 2 to entry: The hydrogen detection apparatus may include one or more built-in alarm indications, output contacts for alarm and/or electrical signals for alarm.

3.11

hydrogen sensing element

component that provides a measurable, continuously changing physical quantity in correlation to the surrounding hydrogen volume fraction

3.12

hydrogen sensor

assembly, which contains one or more hydrogen sensing elements and may also contain circuit components associated with the hydrogen sensing elements, that provides a continuously changing physical quantity or signal in correlation to the physical quantity provided by the hydrogen sensing element(s)

3.13

hydrogen volume fraction

hydrogen content expressed as the ratio of the volume of hydrogen to the total volume of all components in the gas mixture under standard conditions of temperature and pressure of 20 °C and 101,325 kPa

3.14

interferant

any substance that affects the sensitivity of a hydrogen sensing element by contacting or adhering to it

3.15

latching alarm

alarm that, once activated, requires deliberate manual action to be deactivated

3.16

measuring range

range, defined by the lowest and highest hydrogen volume fractions, within which a hydrogen detection apparatus can measure hydrogen volume fractions within the specified accuracy

3.17

multi-level detection

continuous detection and monitoring of hydrogen volume fraction with multiple alarm set points

3.18

nominal supply voltage

voltage corresponding to the manufacturer-recommended operating voltage for the hydrogen detection apparatus

3.19

poisoning

phenomenon caused by any interferant that permanently affects the sensitivity of a hydrogen sensing element

3.20

remote hydrogen sensor

hydrogen sensor that is remotely connected to a hydrogen detection apparatus

3.21

selectivity

response of the hydrogen detection apparatus to hydrogen compared with the response to other gases

Note 1 to entry: If there is high selectivity to hydrogen, the results will be less ambiguous and the cross-sensitivity to other gases will be low.

3.22

sensitivity

ratio of change produced in the apparatus by a known volume fraction of hydrogen

Note 1 to entry: Depending on the context, this can refer to the minimum change in the volume fraction of hydrogen that the apparatus will detect.

Note 2 to entry: High sensitivity implies that low volume fractions can be measured.

3.23

special state

state of the hydrogen detection apparatus other than those in which monitoring of hydrogen volume fractions takes place, for example, warm-up, calibration mode or fault condition

3.24

stabilization

state in which three successive readings of a hydrogen detection apparatus, taken at 30 s intervals, indicate no changes greater than 5 % of the volume fraction of the test gas

3.25

test gas

mixture of hydrogen and clean air with a known volume fraction, which is used for performance tests of hydrogen detection apparatus

3.26

time of response

t₉₀

time interval, with the hydrogen detection apparatus in a warmed-up condition, between the time when an instantaneous variation from clean air to the standard test gas is produced at the inlet of the remote hydrogen sensor or the integrated hydrogen sensor(s) and the time when the response reaches a stated percentage ( x ) of the final indication

3.27

time of recovery

t₁₀

time interval, with the hydrogen detection apparatus in a warmed-up condition, between the time when an instantaneous variation from the standard test gas to clean air is produced at the inlet of the remote hydrogen sensor or the integrated hydrogen sensor(s) and the time when the response decreases to a stated percentage ( x ) of the final indication

3.28

warm-up time

time interval between the time when the hydrogen detection apparatus is switched on and the time when the special state indicator is turned off, showing that the hydrogen detection apparatus is in a warmed-up condition