ISO 3530:1979 真空技術—質量分析計タイプのリークディテクタキャリブレーション | ページ 4

2.1.1

バックグラウンド

一般に、注入されたサーチガスなしでリークディテクターによって与えられるスプリアス指示の合計。バックグラウンドは、質量分析計のチューブ (以下を参照) または関連する電気および電子回路、あるいはその両方で発生する可能性があります。 （多くの場合、この用語は、注入された探索ガスから生成されたイオン以外のイオンによる兆候を具体的に指すために使用されます。）

2.1.2

ドリフト

背景の比較的ゆっくりした変化。重要なパラメータは、指定された期間に測定された最大ドリフトです。

2.1.3

ノイズ

背景の比較的急速な変化。重要なパラメータは、指定された期間に測定されたノイズです。

2.1.4

ヘリウムの背景

漏れ検出器または漏れ検出システムの壁から放出されたヘリウムによるバックグラウンド。

2.2.1

inlet line or sample inlet line

The line through which the search gas passes from the object under test to the leak detector.

2.2.2

inlet valve

A valve which is placed at the end of the sample inlet line and adjacent to the leak detector. (See figure 1.) Almost invariably the inlet valve is an integral part of the leak detector.

2.2.3

leak isolation valve

A valve placed between a leak which is to be used for testing the leak detector and the sample inlet line. (See figure 1.)

2.2.4

pump valve

A valve placed between the roughing pump used for evacuating the sample inlet line and that line. (See figure 1.)

2.2.5

vent valve

A valve used to admit air or other gas into an evacuated space so as to increase the pressure therein to atmospheric pressure. (See figure 1.)

2.2.6

backing-off control

zero control

An electrical control, present on most leak detectors, which may be used to shift the output indication of the device. Frequently, the backing-off control is used to return the output indication to zero of the scale, whence the alternative name.

2.2.7

filament

The source of the (thermal) electrons which ionize the gases in the mass spectrometer tube; the filament is located in this tube.

2.2.8

mass spectrometer tube

That element of a leak detector in which the search gas is ionized and detected.

2.4.1

leak

n

2.4.2

channel leak

A leak which consists of one or more discrete passages that may be ideally treated as long capillaries.

2.4.3

membrane leak

A leak which permits gas flow by permeation of the gas through a non-porous wall. For helium, this wall may be of glass, quartz, or other suitable material.

2.4.4

molecular leak

A leak through which the mass rate of flow is substantially proportional to the reciprocal of the square root of the molecular mass of the flowing gas.

2.4.5

viscous leak

A leak through which the mass rate of flow is substantially proportional to the reciprocal of the viscosity of the flowing gas.

2.4.6

calibrated leak

A leak device which provides a known mass rate of flow for a specific gas under specific conditions.

2.4.7

standard leak

A calibrated leak for which the rate of leakage is known under standard conditions; namely, 23 ± 7 °C, a pressure of 100 kPa ± 5 % at one end of the leak, and a pressure at the other end so low as to have a negligible effect on the leak rate.

2.4.8

virtual leak

The semblance of a leak due to evolution of gas or vapour within a system.

2.5.1

leak rate

The throughput ¹⁾, in Pa·m³·s^-1, of a specific gas which passes through a leak under specific conditions.

2.5.2

standard air leak rate

The throughput, through a leak, of atmospheric air of dewpoint less than - 25 °C under standard conditions specified as follows: the inlet pressure shall be 100 kPa ± 5 %, the outlet pressure shall be less than 1 kPa, and the temperature shall be 23 ± 7 °C.

2.5.3

equivalent standard air leak rate

Short-path leaks having standard air leak rates less than 10 ^-7 to 10^-8 Pa·m³·s^-1 are of the molecular type (see 2.4.4). Consequently, helium (relative molecular mass 4) passes through such leaks more rapidly than air (relative molecular mass 29,0), and a given flow rate of helium corresponds to a smaller flow rate of air. In this International Standard, helium flow is measured and the"equivalent standard air leak rate" is taken as times the helium leak rate under standard conditions (see 2.5.2).

2.6.1

peak

n

The trace showing a maximum on the chart recorder when the leak detector is mass scanned (see below) with gas present, usually the search gas, to which the detector is sensitive.

2.6.2

peak

v

To so set the scanning control (see 2.6.3) of a leak detector that the output due to a given search gas input is maximized. A form of tuning.

2.6.3

scan

v

To vary the accelerating voltage (or other equivalent operating parameter) of a leak detector, particularly across that range of voltage which includes the voltage necessary to produce a search gas peak.

2.6.4

tune

v

In leak-detection technology, to adjust one or more of the controls of a leak detector so that its response to a search gas is maximized. Tuning by means of the scanning control only is called"peaking".

2.6.5

zero

v

To adjust the backing-off or zero control so that the output indication of the leak detector is at the zero of the indicating scale or at some other reference point.

2.7.1

concentration ratio

Same as mole fraction (2.7.2).

2.7.2

mole fraction

The ratio of the number of atoms (or molecules) of a given constituent of a mixture to the total number of atoms (or molecules) in the mixture. For ideal gases, the mole fraction has the same value as the fraction based on volume; in general, leak detectors are operated in the pressure range where gases behave ideally. Same as concentration ratio.

2.7.3

partial pressure

In a mixture of gases, the partial pressure of a constituent is the product of the total pressure of the mixture and the mole fraction or concentration ratio of the given constituent.

2.8.1

sensitivity

The sensitivity of a device is the change in output of the device divided by the change in input which caused the response.

2.8.2

minimum detectable signal

An output signal due to incoming search gas which is equal to the sum of the noise and the drift.

2.8.3

minimum detectable leak

minimum detectable leak rate

Note 1 to entry: One of the purposes of this International Standard is to describe practical procedures for determining minimum detectable leak rate, taking into account background, volume rate of flow (pumping speed), and time factor.

2.8.4

minimum detectable concentration ratio

Thesmallest concentration ratio of a given search gas in an air mixture that can be detected unambiguously by a given leak detector when the mixture is fed to the detector at such a rate as to raise the pressure in the instrument to some optimum high value. In this International Standard, the minimum detectable leak rate is calculated — by a somewhat arbitrary procedure — from observations of the response of the leak detector to a helium-air mixture of known helium concentration ratio (see 3.5).

2.9.1

time constantr

τ

The time interval required for the output of an instrument or system to change by 1 — 1/e or 63 % of the ultimate (steady-state) output change produced by an abrupt change in input.

2.9.2

response time

The time constant corresponding to a change from a zero or small leak-rate indication, to a positive or larger leak-rate indication.

2.9.3

cleanup time

clearing time

The time constant corresponding to a change from a positive leak-rate indication to a small or zero leak-rate indication.

Note 1 to entry: In this International Standard response time and cleanup time are assumed to be equal.