As flow passes through the device, it is directed onto the very small teeth of the wheel using a precision-machined nozzle. On the opposite end, turbine flow meters operate by utilizing the Pelton turbine wheel concept. This advantage offers flexibility not found on many other types of flow sensors. Therefore, if a unit is calibrated for air, it is a relatively simple calculation to figure the calibration for nitrogen or some other similar gas. The output of the thermal mass flow sensor is directly related to the specific heat characteristic of the gas being measured. McMillan’s patented system insures that the zero remains stable and the sensor is extremely repeatable. As the gas passes through the tube, the smart electronics sense the amount of heat transferred from one coil to the other. The first coil introduces a small amount of heat into the gas stream. As flow enters the device, a small portion is redirected into a small tube containing two coils – one downstream from the other. Thermal mass flow meters operate by utilizing thermal sensing technology. In the following comparison, we will primarily focus on the principles of operation for thermal mass flow meters and turbine flow meters for volumetric flow. Mass and volumetric flow meters also vary in the way they operate and function to measure flow. Some examples of devices that measure volumetric flow rates include:
Some examples of devices that measure mass flow rates include: Various Types of Mass Flow and Volumetric Flow MetersĪnother key difference when it comes to mass and volumetric flow meters are the various types of instruments available for each flow meter and are selected depending on the desired application. It is also important to keep in mind that there are various types of substances that can pass through a flow meter such as liquids and gases. In volumetric flow meters, the flow rate is calculated by measuring the volume of a substance through a device over a given period. In mass flow meters, the flow rate is calculated by measuring the amount of mass of a substance passing through a device for a given amount of time.
Each type has its own set of benefits and can be used across many industries and for various applications.Īs part of McMillan’s mission to solve the many challenges encountered in instrumentation and equipment design, this helpful article will serve as a reference to help you distinguish the differences between mass and volumetric flow meters: Differences in Flow Measurementįor starters, let’s review the differences between mass and volumetric flow rates as it is common for some people to confuse mass flow rates and volumetric flow rates with velocity or air speed. Therefore, it is just as important to determine if your application requires a mass flow meter or a volumetric flow meter. However, this cannot happen if you are using the wrong type of flow meter or incorrectly installing your instrument. During your research and discovery process of searching for flow measurement products, have you taken the time to consider whether your organization requires mass or volumetric flow meters?Īs an engineer or technician, getting repeatable and accurate measurements from your flow meter is critical.