What is the difference between PAS and gas chromatography for DGA?

Photoacoustic spectroscopy (PAS) and gas chromatography (GC) are two different measurement technologies for DGA. PAS uses optical absorption and acoustic detection — it requires no carrier gas, no consumables, and minimal maintenance, making it ideal for online and field-portable monitoring applications. GC separates gases in a chromatography column and detects them with FID/TCD detectors — it offers slightly higher sensitivity but requires carrier gas cylinders, regular column replacement, and skilled operation, making it better suited to laboratory use. Many utilities use both: PAS monitors for continuous online surveillance of critical transformers, and laboratory GC for periodic reference testing across the fleet.