Which two types of flow meters are commonly used?

The two types of flow meters that are commonly used in various applications include ultrasonic and magnetic flow meters. Ultrasonic flow meters work by sending ultrasonic sound waves through the fluid and measuring the time it takes for the waves to travel upstream and downstream. This time differential allows for precise measurements of fluid velocity and, consequently, flow rate. Magnetic flow meters operate based on Faraday's law of electromagnetic induction, where a magnetic field is applied to a conductive fluid, and the induced voltage is measured to determine flow.

While thermal flow meters, which measure the heat transfer from a heated element to the fluid, and rotameters, which use a float in a conical tube to measure flow, can be found in specific applications, they are not as widely applicable across different types of fluids and conditions as ultrasonic and magnetic flow meters. Similarly, spring probes and paddlewheel meters are specialized tools that have their specific uses and may not offer the versatility or accuracy needed in many situations. Electromagnetic and differential pressure flow meters are used but may not be as broadly utilized as the ultrasonic and magnetic types. Thus, the combination of ultrasonic and magnetic flow meters represents the most common pair in general use across various industries.