Measuring appts. for small particles in flowing medium - uses HF ultrasonic Doppler principle with two measurement positions, each with ultrasonic transmission reception transducer, and mixers to produce difference signals

摘要

The small particles in a flowing medium in a measurement tube (1) with small internal dia. are measured using the high frequency ultrasonic Doppler principle. Two measurement positions (3,3') each consisting of a transmission and reception transducer (5,20) mounted externally on the tube, are mounted a distance apart. Each has an associated mixer (27,28) which generates a difference signal from the transmitted and received frequencies. A further mixer (30) generates a differnce signal from the outputs of the two measurement position mixers. USE/ADVANTAGE - For measurement of number of particles per unit volume or mass, also allows calculation of exact particle size, esp. for impurity measurements on lubricating oil. Produces sharp Doppler signals only from detected particles, even when their ultrasonic impedance differs only slightly from that of carrier medium.