Mass Flow Controlled(MFC):
The Mass Flow Controller uses a hot wire anemometer to maintain a steady flow rate throughout the sampling period. The hot wire anemometer is inserted into the flow channel and detects changes in thermal mass to increase or decrease the motor speed.
Volumetric Flow Controlled(VFC): The VFC controller is a critical orifice with a predetermined hole diameter. The critical orifice is calibrated in a NIST traceable lab to determine the volumetric flow rate. The motor runs wide open and as air passes through the critical orifice,the sampler runs at a predetermined flow rate.
PLUS Technology (MFC): The PLUS technology MFC uses ambient temperature, ambient pressure, and a hot wire anemometer to maintain the set flow rate. This is the most accurate flow controller available. It also features and auto calibration function and digital timer.
PLUS Technology (VFC): The Plus Technology volumetric flow controller uses a combination of the critical orifice and the PLUS controller to calculate the ambient flow rate. The system uses the temperature, barometric pressure, and orifice pressure to calculate and record the ambient flow rate. The system also includes a digital timer.