Frequently Asked Questions on UDV Applications
How to install ultrasonic transducers?
The main important point
is to insure a good coupling between the transducer and the liquid. Any gas
interface is not allowed because gas has a very low acoustic impedance and therefore
reflects all the ultrasonic energy.
The best coupling is realized when the transducer is immersed in the liquid.
All Signal Processing's transducers can be completely submerged in any liquid
which is not chemically aggressive. The housing of the transducer is made of
stainless steel and the front surface is made of epoxy. Other material
for the housing can be also available. When it is not possible to immerse the
transducer and a solid wall has to be crossed, an ultrasonic coupling gel is
used.
Normally the transducers are delivered with a standard cable of 1.5 meter, but longer cable can be used. The only requirement is to use a 50 ohm cable, like any RG174 or RG58 cable. Using a cable longer cable then 10 meters can induce some noise in the measurement and some loss in sensitivity.
Is it possible to apply UDV in gas?
Unfortunately not. There are two main reasons for this. The attenuation of ultrasonic waves is very strong at the frequencies used and it is very seldom to find particles of compatible dimensions that can follow the gas flow. Nevertheless it is possible to measure the velocity of a solid surface if a small gap exists between the transducer and the moving surface (in the order of few centimeters).
Ultrasonic Doppler velocimetry is almost the unique technique that is capable to measure in real time a velocity profile in mud. Despite the high degree of attenuation of mud, successful measurement can be realized up to concentration of sand in the order of 30%.
Ultrasonic Doppler velocimetry was originally developed for medical applications. Our ultrasonic velocimeters have been used for many years in the medical field to investigate blood flows in the venous and arterial system. Signal Processing has obtained the EN46001 certification in order to help our customers to use our equipment in the medical field.