Echotel® 940/941 compact economical ultrasonic level switches

Echotel® Model 940 and 941 Ultrasonic Level Switches are compact integral units that utilize pulsed signal technology to perform high or low level measurement in a wide variety of liquid applications. These switches feature a 316 stainless steel tip-sensitive transducer that is offered in a variety of NPT, flanged, and sanitary process connections. The compact electronics are completely encapsulated just above the process fitting. The Model 940 offers a 1-amp SPDT relay output. The Model 941 has a mA current shift output.

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The product

Ultrasonic contact technology

Ultrasonic contact switches use a pair of piezoelectric crystals that are encapsulated in epoxy at the tip of the transducer for level measurement. 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 electrical signal.

Features

Pulsed electronics for excellent performance in difficult process conditions and superior immunity from sources of electromagnetic noise
Advanced transducer design provides reliable operation by draining viscous liquids and ignoring foam in turbulent applications
Suitable for SIL (Safety Integrity Level) 2 loops (FMEDA analysis data available)
Extremely compact unit is easily installed in areas where access space is limited
No calibration or configuration necessary
1 amp SPDT relay output (940), 8/16 mA current shift output (941)

Operating principle

Ultrasonic energy detects the presence or absence of liquid in a tip sensitive transducer gap. The principle behind contact ultrasonic 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 converts 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.