Echotel® Model 961 Ultrasonic Level Switches use pulsed signal technology for superior performance in difficult process conditions, and to provide excellent immunity from sources of electrical noise interference. Extensive self-testing of the electronics and transducer make this advanced switch suitable for a wide variety of hygienic level switch applications.
Model 961 is offered with either a 5-amp relay or a current shift electronics. The relay output electronics has a DPDT relay for level detection, and a SPDT malfunction relay. The current shift version indicates 8 mA during normal operation, 16 mA as a level alarm condition and a user-selectable 3.6 or 22 mA malfunction indication.
The Model 961 switches are designed for the stringent requirements of hygienic applications. These switches are offered with a deep-drawn 304 stainless steel housing that is favorable to CIP and SIP procedures. A 20 Ra surface finish is featured with hygienic Model 961 transducers. These transducers are available with 11⁄2" and 2" Tri-Clamp® fittings, and DN65 Varivent® Type N flanges.

Operating Principle

Model 961 switches use pulsed signal technology to detect the presence or absence of liquid in an ultrasonic transducer gap. The transducer uses a pair of piezoelectric crystals that vibrate 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 and converts it back into an electrical signal. This signal is sent to the electronics to indicate a wet gap condition. When no liquid is present, the ultrasonic signal is attenuated and is not detected by the receive crystal.
Challenging process conditions like aeration, suspended solids, and high viscosities are overcome by using pulsed signal circuitry in Model 961 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.


- Mixing and blending vessels
- DI/WFI applications
- Solvent storage
- Biowaste tanks
- Sterile liquid media tanks
- CIP buffer tanks


- Self-test technology provides unsurpassed reliability and testing of electronics, transducer, piezoelectric crystals, and electromagnetic noise
- 20 Ra surface finish with Tri-Clamp and Varivent fittings
- Adjustable time delay for turbulent aerated liquids - Tip-sensitive transducer measures level within 1⁄4" of the vessel bottom
- Pulsed signal technology provides superior performance in difficult process conditions


- Deep drawn 304 stainless steel or cast aluminum housings
- Glass window cover
- NPT, Tri-Clamp, or Varivent process connections


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