Rotary meters step forward in commercial and industrial appliances with their wide measurement ranges and compact sizes.  There is no need to use straight tube in meter input and output since rotary meters also perform volumetric measurement just like diaphragm meters.  While 16 bars and 20 bars designs are more common, rotary meters capable of working at 100 bars can also be manufactured.

Working Principle:

Two 8 shaped rotor with their axes parallel to each other is placed perpendicularly to gas flow direction and chambers forming between these rotors and meter body enable volumetric measurement.  Rotation movements of rotors are transferred to the numerator mechanically.  Gear groups below the numerator and behind the meter must be lubricated in order for them not to get affected by mechanical wear-out, and oil levels must be checked and renewed in periods specified in the user's manuals.  You must make during assembly of the meter that gears at both sides work in oily environment, i.e. rotor axes of the meter must be parallel to the ground.