Differential Pressure flow meters measure the velocity of fluids by reading the pressure loss across a pipe constriction. These meters can contain laminar plates, an orifice, nozzle, or Venturi tube to create an artificial constriction. Highly sensitive pressure sensors measure the pressure before and after the constriction. According to Bernoulli's principle, the pressure drop across the constriction is proportional to the square of the flow rate. The higher the pressure drop, the higher the flow rate.

Differential pressure flow meters utilize a robust, time proven measuring technique for a wide range of clean liquids and gases. The meters are available in a wide range of line sizes with wide temperature and pressure ranges. Installation is relatively easy and the meters often offer temperature and pressure measurements as well, measurements of mass flow compensation . Care should be taken with highly viscous liquids, though, as accuracy can be adversely affected or not achieved.

Selecting a Flow Meter

The basis of good flow meter selection is a clear understanding of the requirements of the particular application. Therefore, time should be invested in fully evaluating the nature of the process fluid and of the overall installation.

  1. What is the fluid being measured by the flow meter(s) (air, water, etc…)?
  2. Do you require rate measurement and/or totalization from the flow meter?
  3. If the liquid is not water, what viscosity is the liquid?
  4. Is the fluid clean?
  5. Do you require a local display on the flow meter or do you need an electronic signal output?
  6. What is the minimum and maximum flow rate for the flow meter?
  7. What is the minimum and maximum process pressure?
  8. What is the minimum and maximum process temperature?
  9. Is the fluid chemically compatible with the flow meter wetted parts?
  10. If this is a process application, what is the size of the pipe?

If you have any questions or need any help selecting a flow meter, please contact us at sales@instrumart.com or 1-800-884-4967 to speak with an applications engineer.