Contact Ultrasonic Level Sensing
FROM
U
ltrasound technology was developed during
WWII under the acronym
SONAR
(SOund
Navigation And Ranging). First applied to
the amplifier becomes as oscillator causing a relay
circuit in the electronics to indicate a wet gap
returns to an idle state.
condition. When liquid vacates the gap, the amplifier
Pulsed-signal
Models 940/941
and
961/962
feature
a digital electronic amplifier
which produces a powerful
pulse of ultrasonic energy five
continuous wave units. This
pulsed-signal technology will
measurement to this day.
ment continues to play a significant role in liquid level
Ultrasonic instruments are made
process control in the 1960s, ultrasonic level measure-
for both contact and non-contact
(or through-air) level sensing. This
of contact ultrasonic products that
provide single and dual point liq-
virtually every process industry.
uid level measurement in
brochure focuses on the Echotel
®
line
to ten times stronger than most
provide more accurate measure-
ment in conditions of aeration,
suspended solids, turbulence,
and highly viscous liquids.
high-frequency ultrasonic
signal units generates pulses of
Continuous-Wave and
Pulsed-Signal Sensing
The transmit crystal of pulse-
is achieved by either continuous-
switch uses two piezoelectric
Ultrasonic contact level sensing
Challenging process conditions such as
suspended solids or aeration are best
managed with pulsed-signal technology.
Models 961/962 switches further minimize
the effects of mild turbulence or splashing
with adjustable time delays.
wave or pulsed-signal technology.
Our
Model 910
continuous-wave
other across the transducer gap.
crystals positioned opposite each
duration. In between each pulse
in the gap the receive crystal
energy only milliseconds in
transmission. If liquid is present
detects the pulse and reports a
the receive crystal “listens” for the
The transmit crystal generates an acoustical signal
signal. When liquid is present in the transducer gap,
which the receive crystal converts into an electrical
wet gap condition to the electronics. When the gap is filled
with air, the receive crystal cannot detect the pulse, and
reports a dry gap condition.
T
2
R
Contact ultrasonic level switches
use ceramic discs called piezo-
electric crystals to transmit and
receive ultrasonic energy. A
transmit crystal (T) is positioned
on one side of a transducer gap
and a receive crystal (R) is posi-
tioned on the opposite side. Tip-
sensitive style gaps—the only
style used on Echotel
®
switches—
can sense level to within
1
⁄
4
" from
the end of the transducer.
MAGNETROL [ MAGNETROL INTERNATIONAL, INC. ]
