Flowmeter

Ultrasonic Doppler flowmeters, are use in industry to measure the flow through a pipe. There big advantage is you don't have to break the line to install. The sensor is affixed to the pipe externally. I use some of these, they work great, however, they are a bit expensive.

So, they are great because:

You don't have to cut the pipe.

One man can install and calibrate in about an hour.

The laser type I've not seen in industry. I believe they are only used medically, to measure blood flow. Perhaps CR4 members know of other applications.

There are several technologies with regards to ultrasonic flow measurement. At least one of those requires you to install a section of pipe with the instrument attached, much like the usual flow meters. The others, like bricktop says, are strap on so you don't need to cut the pipe. Personally, I haven't used them but I've seen demos and I'm quite impressed with them. I was impressed enough to actually purchase one. 'Still waiting for it to arrive though.

I am not aware of a laser type flow meter that measures flow directly. I am aware of a weir type flow meter that uses a laser to measure the height of the weir which can be converted to equivalent flow.

I knew that both had the same principles. Ultrasound gets deviated cause the flow and laser little too but it depends most of the amount of particles the flow has.

Blood flow can be measured through the use of a monochromatic laser diode. The laser probe is inserted into a tissue and turned on, where the light scatters and a small portion is reflected back to the probe. The signal is then processed to calculate flow within the tissues. There are limitations to the use of a laser doppler probe; flow within a tissue is dependent on volume illuminated, which is often assumed rather than measured and varies with the optical properties of the tissue. In addition, variations in the type and placement of the probe within identical tissues and individuals result in variations in reading. The laser doppler has the advantage of sampling a small volume of tissue, allowing for great precision, but does not necessarily represent the flow within an entire organ. The flow meter is more useful for relative rather than absolute measurements. This is all about Laser Doopler type Flowmeter In Ultrasonic Flowmeter there are two types, Doopler type and transit time type. Laser type are used flow small diameter tissues and blood viens where it is not practically used in the heavy industry. But Ultrasonic is widely used in the heavy industry.