961-20A0-010 Datasheet, PDF (4/36 Pages) Magnetrol International, Inc. – Ultrasonic Single and Dual Point Level Switches

1.0 Introduction
ECHOTEL Model 961 and 962 ultrasonic level switches
utilize pulsed signal technology to detect high, low, or dual
point level in a broad range of liquid media applications.
Model 961 is a single point level switch. Model 962 is a
dual point switch used as a level controller or to control
pumps in an auto-fill or auto-empty mode.
1.1 Principle of Operation
Ultrasonic
transducer
Transmit
crystal
Receive
crystal
Figure 1
Ultrasonic Signal Transmission
Across Transducer Gap
Model 961/962 switches utilize ultrasonic energy to detect
the presence or absence of liquid in a single or dual point
transducer. Ultrasonic contact level technology uses high-
frequency sound waves that are easily transmitted across a
transducer gap (see Figure 1) in the presence of a liquid
media, but are attenuated when the gap is dry. Model
961/962 switches use an ultrasonic frequency of 2 MHz to
perform this liquid level measurement 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 elec-
tronics 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 electrical
signal. This signal is sent to the electronics to indicate the
presence of liquid in the transducer gap. When there is no
liquid present, the ultrasonic signal is attenuated and is not
detected by the receive crystal.
2.0 Installation
2.1 Unpacking
Unpack the instrument carefully. Inspect all units for
damage. Report any concealed damage to carrier within
24 hours. Check the contents of the packing slip and
purchase order. Check and record the serial number for
future reference when ordering parts.
serial number
4
51-646 Echotel^® Model 961 & 962 Ultrasonic Level Switches