960-58A0-031 Datasheet, PDF (2/8 Pages) Magnetrol International, Inc. – Echotel® Model 960 AS-Interface® Ultrasonic Level Switches

TECHNOLOGY
BASIC OPERATION
Model 960 switches utilize ultrasonic energy to detect the
presence or absence of liquid in a single point transducer.
Ultrasonic contact level technology uses high-frequency
sound waves that are easily transmitted across a transducer
gap in the presence of a liquid media, but are attenuated
when the gap is dry. Model 960 switches use an ultrasonic
frequency of 2 MHz to perform this liquid level measure-
ment in a wide variety of process media and application
conditions.
The transducer uses a pair of piezoelectric crystals that are
encapsulated in epoxy at the tip of the transducer. The
crystals are made of a ceramic material that vibrates at a
given frequency when subjected to an applied voltage.
The transmit crystal converts the applied voltage from the
electronics into an ultrasonic signal. When liquid is present
in the gap, the receive crystal senses the ultrasonic signal
from the transmit crystal and converts it back to an elec-
trical signal. This signal is sent to the electronics to indi-
cate the presence of liquid in the transducer gap. When
there is no liquid present, the ultrasonic signal is attenu-
ated and is not detected by the receive crystal.
Ultrasonic
transducer
Transmit
crystal
Receive
crystal
Ultrasonic signal transmission
across transducer gap
PULSED SIGNAL TECHNOLOGY
Challenging process conditions such as
aeration, suspended solids, and high
viscosities are easily handled with the
pulsed signal technology utilized in the
960 switches. Pulsed signal circuitry
drives the transmit piezoelectric crystal to produce
powerful pulses of high-frequency ultrasonic energy.
These ultrasonic pulses are readily transmitted through
liquids, but are attenuated when the transducer gap is dry.
This technology also provides excellent immunity from
electromagnetic noise interference.
Pulsed signal technology makes the 960 units more reli-
able than older continuous wave ultrasonic switches.
Unlike many tuning forks, pulsed signal ultrasonic
switches do not need to be configured for different media
densities, making these units the most universally applied
level switches on the market today.
ADJUSTABLE TIME DELAY
Turbulence and splashing can cause
some fixed time response switches to
produce false level alarms. Model 960
switches overcome this difficulty with an
adjustable time delay feature.
A potentiometer allows a ¹â„2 to 45-second delay to be set
to disregard waves or splashes, and reliably detect the
true liquid level.
2