A helium leak detector permits the localization of leaks and the quantitative determination of the leak rate, i.e. the gas flow through the leak. Such a leak detector is therefore a helium flow meter. In practice the leak detector performs this task by firstly evacuating the part which is to be tested, so that gas from the outside may enter through an existing leak due to the pressure difference present. If only helium is brought in front of the leak (for example by using a spray gun) this helium flows through the leak and is pumped out by the leak detector. The helium partial pressure present in the leak detector is measured by a sector mass spectrometer and is displayed as a leak rate. This is usually given in terms of volume flow of the helium (pV-flow).
Important Specifications
The two most important features of a leak detector are its measurement range (detection limits) and its response time.
The measurement range is limited by the lowest and the highest detectable leak rate. The lowest detectable leak rate is defined by the sum of drift and noise in the most sensitive measurement range. Usually the sum of noise amplitude and zero drift per minute is made to be equivalent to the lowest detectable leak rate. With leak detectors the amount of drift is so low, that the noise amplitude alone determines the detection limit.
The highest detectable leak rate depends strongly on the method employed. Especially the counterflow method and partial flow operation (see description below) permit the measurement of very high leak rates even with a sensitive helium leak detector. In addition the multistage switchable high impedance input amplifiers of the leak detectors also permit the measurement of high leak rates.
In practical applications, especially in the localization of leaks the response time is of great significance. This is the time it takes from spraying the test object with helium until a measured value is displayed by the leak detector. The response time of the electronic signal conditioning circuitry is an important factor in the overall response time. In the case of leak detectors the response time of the electronic circuitry is well below 1 s.
The volume flow rate for helium at the point of the test object is of decisive significance to leak detection on components which are pumped down solely by the leak detector. This volume flow rate provided by the leak detector takes care of the helium entering through a leak and it ensures quick detection by the leak detector. On the other hand the volume of the test object delays the arrival of the helium signal. The response time can be calculated on the basis of the following simple equation:
Response time for helium tA = 3
(for 95% of the final value)
with V = Volume of the test object SHe = Volume flow rate for helium at the point of the test object (or at the inlet of the leak detector, if it alone pumps down the test object).
Helium Leak Detector PhoeniXL 300
The PhoeniXL 300 is a portable multipurpose helium leak detector and equally well suited to both service and series production testing. Its rugged design and its ease of use make the PhoeniXL 300 to a userfriendly leak detector in its class.
Advantages to the User
Lowest detectable leak rate
Short He recovering time condition
Quick start-up
Extremely fast response time
Oil-free gas admission system
One of the smallest helium leak detectors in the world
High sensitivity
Fast leak rate readout also at low leak rates
Typical Applications
Leak tests in connection with
Quality assurance
Automotive industry
Analytical instruments
Systems manufacture
Power station engineering
Research and development
Semiconductor industry
High vacuum and ultra-high vacuum engineering
Ideal tool for industrial series production testing – in the cooling and air conditioning industries, for example
In connection with the sniffer lines which are available as accessories the PhoeniXL 300 may also be used as a sniffer leak detector. In connection with a partial flow pump set the PhoeniXL 300 may also be used for the detection of leaks on large vessels.
