Gas density sensors function electronically using comparison measurements from two oscillating quartz crystals.
The consistent resonant frequency of a quartz oscillator under vacuum is compared with the resonant frequency of an identical quartz situated in the sample gas. The difference in the resonant frequency is proportional to the density of the sample gas. This difference is processed into a digital or analog output signal. In addition, the temperature can be measured via the pulse width of the frequency system.
Gas density sensors are maintenance-free.