Principles of Operation
Metered gases are divided into two laminar flow paths, one through the primary flow conduit, and the other through a capillary sensor tube.
Both flow conduits are designed to ensure laminar flows and therefore the ratio of their flow rates is constant.
Two precision temperature sensing windings on the sensor tube are heated, and when flow takes place, gas carries heat from the upstream to the downstream windings. The resultant temperature differential is proportional to the change in resistance of the sensor windings.
A Wheatstone bridge design is used to monitor the temperature dependent resistance gradient on the sensor windings which is linearly proportional to the instantaneous rate of flow.
Output signals of 0 to 5Vdc and 4 to 20mA are generated indicating mass molecular based flow rates of the metered gas.
Flow rates are unaffected by temperature and pressure variations within stated limitations.
Rigid metallic construction
Maximum pressure of 500 PSIG (34.5 bars)
Leak integrity 1 x 10-7 of helium
Built-in tiltable LCD readout
0-5 Vdc and 4-20 mA signals
Can be used as a portable device
Engineering units or 0 to 100% displays