A CNG leak tester sounds like it should just measure whether pressure holds steady. The actual engineering problem is that pressure doesn't hold steady on its own -- temperature moves it too, and separating the two is the whole game.
Neometrix's CNG Vigilant tests complete CNG vehicle circuits and critical components -- regulators, cylinder valves, nozzles, pressure lines -- at pressures up to 350 bar, using pressure decay plus differential pressure sensing (Ver. 0.30, resolving to 1×10⁻⁹ atm cc/sec) or optional Helium Mass Spectrometry (Ver. 0.34, resolving to 1×10⁻¹⁰ atm cc/sec).
The temperature problem is bigger than it sounds: even a 1°C shift can create a pressure error of nearly 1 bar in a 100 cc volume at 300 bar. A naive pressure-decay test can't distinguish a genuine leak from thermal drift -- which means without correction, a system either throws false alarms on good parts or lets real leaks slide through underneath a cooling trend. TTLIV (Temperature-Time-Logic-Integrated-Volume) technology solves this by calibrating for up to 5 different circuit volumes and using software-controlled fill rates to isolate the pressure drop that's actually caused by a leak.
The rest of the system is designed to remove the operator from the loop: one-touch remote test initiation up to 10 meters away, stepwise pressurization that catches loose fittings before full test pressure is reached, and automatic nitrogen reclaim across up to 4 auto-switching cylinders so the line never stops for a gas change.
Full writeup: https://neometrixgroup.com/products/cng-vigilant
