990 CLD Autoline™ Leak Detector
6-2
DRAFT 2/2/04
Terminology
The following terminology applies throughout this manual:
Rate-of-Rise
(Vacuum Systems)
This is defined as the rate of increase of absolute pressure per unit
time with the vacuum pump isolated from the system, and is the
sum of actual inleakage and internal outgassing. The rate of rise is
usually expressed in Torr or microns (milliTorr) per hour.
Flow
std cc/sec
One cubic centimeter of gas per second
at a pressure of one standard atmosphere
(760 Torr at 0 °C or 32 °F).
atm cc/sec-
One cubic centimeter of gas per second
at ambient atmospheric pressure and
temperature. Used interchangeably with
std cc/sec
because the difference is
insignificant for leak-testing purposes)
Conversions
1 std cc/sec
=
0.76 Torr-liter/sec for practical purposes, equal
1 torr-liter sec = 1.3 std cc/sec
1 std cc/sec
= 9.7x104 micron cubic feet per hour
or practically 10
5
micron CFH (
υ
CFH)
1 CFH
= practically 10
-5
std cc/sec
1 std cc/sec
= 0.1 Pascal cubic meters/sec
Numerical Notation -
Exponential System
Most leak rates of commercial significance are very small fractions
of a std cc/sec. Therefore, minus powers of ten are used as a
convenient system of numerical shorthand:
1x10
−
1
= 1x1110
= 0.1
1x10
−
2
=
1x1110
x1110
=
0.01
5x10
−
3
= 5x1110x1110x1110
= 0.005
1x10
−
3
= 1x1110x1110x1110
= 0.001
1x10
−
6
= 1x1110x1110x1110x1110x1110x1110 = 0.000001
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