Sheet #673u – Definition, characteristics and measurement principles
Version 1.04a  User guide ATEQ 6th series Page 2/7 
3. THE DIFFERENT TESTS 
3.1. LEAK TEST
The leak test is most suitable for measuring small leaks (pressure drop). The following formula 
is used to convert a leak expressed in units of flow to a drop in pressure: 
)(cm V x0,0006
/min)(cmF
(Pa/s)P
3
3
 '
F(cm
3
/min)   =   leak flow 
V (cm
3
)  =  volume of the test part 
'P (Pa/s)  =  pressure drop 
Example:
Part which has dP/dt = 50 Pa/s  Part which has dP/dt = 1 Pa/s 
Test
1 s 
2 s 
3 s 
.
.
n s 
Pa/s
50
50
50
.
.
50
Pa
50
100
150
.
.
nx50
Test
1 s 
2 s 
3 s 
.
.
n s 
Pa/s
1
1
1
.
.
1
Pa
1
2
3
.
.
n
The choice of working in Pa or in Pa/s depends on the application. 
In all events, it must not be forgotten that the range of the sensor in Pa or Pa/s is limited to 50, 
500 or 5000 Pa depending on the instrument configuration. 
3.1.1.  The main types of measurement 
There are three measurement methods:
¾ Direct measurement,  
¾ Indirect measurement, 
¾  Sealed component measurement.  
These three principles concern measurements carried out under pressure and under vacuum.
The configuration is determined by the application, and must be determined before ordering the 
instrument.