Differential pressure flowmeters use Bernoulli's equation to measure the flow of fluid in a pipe. Differential pressure flowmeters introduce a constriction in the pipe that creates a pressure drop. When the flow increases, more pressure drop is created. Bernoulli’s equation states that the pressure drop across the constriction is proportional to the square of the flow rate. Laminar flow elements, however, present a special case wherein the fluids are in a laminar regime (low Reynolds number) and the pressure drop is linear in relation to the flow rate. This makes it very useful for reading the low end of the scale and increases the “turn down” from the usual 10:1 to 100:1. This technology is optimal for clean gas flows. The flow is calculated by measuring differential pressure and making corrections with data from temperature and absolute pressure sensors.
Laminar flow elements meter inferentially. Use only when the gas is clean and dry and within the pressure and temperature limits of the sensors.
Laminar flow element flowmeters are generally applicable to industrial gas flows in most industries, such as shielding gas, airflow in painting robotics, or any industry using common industrial gases such as Carbon Dioxide, Air, Nitrogen, Hydrogen, Helium or Argon.
Because of the precise geometry required, the gas must be clean and dry. Air from a compressor must go through a drier.