910 Datasheet, PDF (2/8 Pages) Magnetrol International, Inc. – ECHOTEL®CONTACTULTRASOUND

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