How does an Ultrasonic flow meter work?

clamp-on flow meter

——Brief introduce the transit-time differential method

ultrasonic flow meter clamp on type

Ultrasonic flow meters are popular for convenient installation and good performance. How does this meter with a pairs of transducers clamp on the pipe? Today I’ll introduce the transit-time differential method, which is the working principle of ultrasonic flow meter.



First,let’s see the two transducers of the meter,from the transparent side you can see there’s white object in the transducer,

transducers for ultrasonic flow meters

that one is the birthplace of ultrasound, which named piezoelectric crystal, it will cause the Piezoelectric Effect, which in short is that the crystal will be vibrate when electrify, and the vibration in certain frequency will cause the Ultrasound.So the piezoelectric effect in piezo crystal is used to produce a short sound pulse. An electrical pulse excites the transducers and the crystal responds with a physical ringing response much the same as a hammer on a bell. That Ultrasonic waves is transferred to the pipe wall and throughout the stream.

transducers for Ultrasonic clamp-on flow meterstransmit time difference for clamp-on flow meters

Ultrasonic waves are transmitted at an angle across fluid in the pipe. Flow is measured by changes in the transit time for the ultrasonic waves. Ultrasonic waves that advance through water will be transmitted slowly when going against flow and conversely, will be transmitted quickly when going along with flow. So we just need to record the time cost of  these two transducers received the ultrasound wave from each other, get the time difference, then divided by the distance between them, the real time speed of flow will be figure out.

principle for clamp on flow meters