INFICON Protec P3000(XL) Helium Leak Detector - Manual (Page 28)

2-1
How the Protec P3000 Works
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2 How the Protec P3000 Works
2.1 Description of the Functions
The Protec P3000 takes in helium through the SL3000 sniffer line, detects the
amount of helium by means of a helium sensitive sensor and converts the sensor
signal into quantitative leak rates.
The Protec P3000 is composed of the following principal subassemblies:
• A Wise Technology sensor as helium detector
• A valve holder for controlling different operating stati
• A diaphragm pump for pumping the gas to the sensor
• An inlet system for the gas flow
• The corresponding electrical and electronic subassemblies for supplying power
and for signal conditioning.
The detector operates under gross vacuum conditions, i. e. the operating pressure
at the detector is several 100 mbar. The under pressure is generated by a diaphragm
pump. The pressure in front of the sensor is measured with a piezo-resistant
pressure gauge and is about 250 mbar under normal operating conditions.
2.2 Description of the Subassemblies
2.2.1 Backing Pump
A diaphragm pump in the Protec P3000 serves as the backing pump. All data and
further information on this pump are given in the Operating Instructions. The backing
pump generates the flow of the gas through the SL3000 sniffer line.
2.2.2 Wise Technology
TM
Sensor
The helium detector (Wise Technology
TM
sensor) consists of a closed glass
container with a measurement device for the precise determination of the pressure
inside the glass housing and a membrane chip with a large number of small quartz
windows. The membrane is permeable only for helium, all other components of air
are retained by the membrane and from the inside of the glass housing. The Quartz
membrane is heated so that the permeation for helium is sufficiently high and fast.
Inside of the glass housing the total pressure is measured precisely. As only helium
can enter the glass housing the total pressure is equal to the partial pressure of
helium. The determined total pressure inside the housing is proportional to the
helium partial pressure outside the sensor.