940-111E-001 Datasheet, PDF (2/4 Pages) Magnetrol International, Inc. – Echotel® Model 940/941 Ultrasonic Level Switch

TECHNOLOGY
Ultrasonic energy detects the presence or absence of liquid in a
tip sensitive transducer gap. The principle behind contact ultra-
sonic technology is that high frequency sound waves are easily
transmitted across a transducer gap in the presence of liquid, but
are attenuated when the gap is dry.
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 con-
verts the applied voltage from the electronics into an ultrasonic
signal. When liquid is present in the gap, the receive crystal is
able to sense the ultrasonic signal from the transmit crystal and
convert 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.
SPECIFICATIONS
Customer
provided
conduit
Ultrasonic
transducer
Transmit
crystal
Receive
crystal
Figure 1
Ultrasonic signal transmission
across transducer gap
Electrical:
Power Supply:
Power Consumption:
Signal Output:
Cabling:
Repeatability:
Response Time:
Environmental:
Ambient Temperature:
Process Temperature:
Maximum Pressure:
Shock
Vibration
Model 940:
Model 941:
12–35 VDC
Less than 1 Watt
SPDT relay, 1 amp @ 30 VDC, 0.5 amp @ 125 VDC, 0.5 amp @ 150 VAC
Dry Gap: 8 mA (±1 mA), Wet Gap: 16 mA (±1 mA)
18" (457 mm) flying leads of 18 AWG wires
0.078" (2 millimeters)
1_{⁄2 second typical}
-40° to +185° F (-40° to +85° C)
-40° to +185° F (-40° to +85° C)
2000 psig (138 bar) for 1" (3 cm) and 2" (5 cm) transducers
1500 psig (103 bar) for transducers longer than 2" (5 cm)
ANSI/ISA-S71.03 Class SA1
ANSI/ISA-S71.03 Class VC2
AGENCY APPROVALS
AGENCY
FM & CSA
APPROVED MODELS
94X-XXXX-XXX
941-XXXX-XXX
PROTECTION METHOD
Non-Incendive
Intrinsically Safe
2
AREA CLASSIFICATION
Class I, Div. 2,Groups A,B,C, & D
Class II, Div. 2, Groups E,F, & G
Class III, Type 4X, IP 66, T4
Class I, Div. 1,Groups A,B,C, & D
Class II, Div. 1, Groups E,F, & G
Class III, Type 4X, IP 66, T4
These units have been tested to EN 50081-2
and EN 50082-2 and are in compliance with
the EMC Directive 89/336/EEC.