
191Fluid Flow
microprocessor built into the transmitter controls. The
microprocessor also detects the voltage of the electrodes
and converters the signal to a uid ow rate. The main
advantages of the magnetic owmeter are that the out-
put signal varies linearly with the ow rate and that the
meter does not obstruct the ow. The major disadvan-
tages are its relative high cost and that it is not suited
for gas ow.
35
9.7.6 Ultrasonic Flowmeter
There are two types of ultrasonic owmeters: time-of-
ight and Doppler. The time-of-ight meter sends pulses
of high-frequency sound waves diagonally across the
pipe as illustrated in Figure 9.37.
50
The t ...