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PDGA™ － Portable Dissolved Gas Analyzer represents a new generation of test equipment for analysis the dissolved gas in oil. PDGA adopted the advanced infrared photo-acoustic spectroscopy technology and the friendly operation interface. The concentration data of the 7 key fault gases and moisture can be drawn directly within 20 minutes in the field. It really can take place of the Gas Chromatography system in the laboratory because of the accurate, rapid, reliable results. Thus the PDGA is one of the best tools for the electric equipment asset evaluation.

Analysis of dissolved gases in the oil is an established technique in this field, and is being further extended to other oil filled equipment, such as power transformers, tap-changers, circuit breakers.
FEATURE:

* Fast measuring in the field :
Within 20 minutes, 7 key fault gases and moisture can be read
* No consumables :
Pure physical photo-acoustic spectroscopy technology,
The consumables of calibration gas and carry gas are needless.
* Moisture in the oil :
The concentration of moisture in the oil can be given during the same one test，±1ppm
* Simple :
Step-by-step software guides and touch screen, the user pass through the procedure.
* Portable and r ed :
Weighs <10 Kg, in a r ed and convenient carry case.
* Reliable :
Engineered design provides inherent reliability and high accuracy.
* DGA diagnosis :
International general faults gases diagnosis method, preset the warning limits.
Roger’s ratios, Duval’s Triangle, IEEE key gases
* PC communication :
External PCs is possible via USB connections, allowing databases to be imported or downloaded.
* Samples : Oil and gas 

THEORY：

The photo-acoustic effect is caused by the ability of a gas to absorb electromagnetic radiation (e.g. infrared light). In absorbing the radiation the temperature of the gas will increase and, if the gas is held in a sealed container, this temperature rise will produce a proportional rise in pressure. If the light source is pulsed the pressure of the gas fluctuates in sympathy and these pressure waves can then be detected using sensitive microphones.

There are two key facts that permit this effect be used for analytical measurements. The first is that each gas has a unique absorption spectrum, thereby allowing the frequency of the infrared source to be tuned to excite a given substance. The second is that the level of absorption is directly proportional to the concentration of the given gas.

Therefore by selecting an appropriate wavelength and measuring the level of the resultant signal it is possible to detect, not only the presence but also the concentration of any given gas, even in a complex cocktail of other compounds. This forms the central principle of Photo-Acoustic Spectroscopy (PAS).

After the gas is extracted from the oil by controlled excitation of the sample it is then analyzed using photo-acoustic spectroscopy, the same method used by the European
Space Agency for monitoring blood gases .

The Diagram illustrates the principle. Pulses of Infrared light are generated using a radiation source and a chopper wheel (Fig 1). These pass through a series of optical filters in turn, Labeled as the wavelength section (Fig 2) .

Each filter is optimized to pass the resonant frequency for a particular gas (e.g. Methane, CH4).The pulses of filtered
IR radiation then pass through the cell containing the sample to be analyzed, as shown in the diagram.

Each particular gas (e.g. CH4) absorbs energy at its resonant frequency, causing a vibration in the molecules. This absorbed energy is quickly released creating small pressure waves.

Two microphones pick up these pressure waves, at the
Frequency of the pulses of IR light, with the amplitude of the signal measured corresponding to the amount of the specific gas present.