Ultrasonic Switches

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Reliable Point-Level Detection for Liquids and Solids

Ultrasonic switches provide dependable point-level detection by using high-frequency acoustic energy instead of mechanical parts. An ultrasonic transducer continuously emits sound pulses into the process media; when liquid or solid material enters the sensing zone, it changes the way these pulses are absorbed or reflected. This shift is detected instantly by the electronics, triggering a high- or low-level alarm, pump control signal, or shutdown action. Because there are no floats, paddles, or moving components, ultrasonic switches maintain long-term accuracy even in demanding environments.
Ultrasonic point switches are well-suited for applications where coatings, buildup, or turbulence can compromise mechanical devices. They work with clean or viscous liquids, slurries, and many types of bulk solids. Installation is straightforward—mount the switch at the required alarm point, ensure the transducer face is unobstructed, and wire to the control system. Most models require no calibration and can be configured on site in minutes.
Cognesense ultrasonic switches, based on our long proven architecture, are engineered for maximum robustness and repeatability. Their solid-state design, rugged housings, and fast response make them a dependable choice for critical alarms, pump protection, and overflow prevention. Whether used in tanks, sumps, hoppers, or chutes, they deliver stable performance and long service life with minimal maintenance.
Sonac 220

What Is an Ultrasonic Switch?

The Sonac 220 is an ultrasonic point level switch designed for reliable on/off control of solids, powders, and granular materials—including lightweight, dusty, or fragile products.
It uses non-contact ultrasonic sensing to detect material presence without moving parts, making it ideal for harsh, abrasive, or sanitary environments where mechanical probes can fail.
The Sonac 220 operates with paired ultrasonic transducers—a transmitter and receiver—that continuously monitor an air path. When material interrupts that path, oscillations drop, and the relay switches state. This technology delivers precise, repeatable level detection even in extreme temperature, vibration, or dust conditions.

Why Use a Switch With a Level Gauge

A switch provides discrete, on/off level control—for example, turning a pump on or off, triggering a high-level alarm, or preventing overflow or dry-run damage.
A level gauge or transmitter, by contrast, delivers continuous measurement (exact level in inches or percent). They work together to ensure safe, redundant performance in storage tanks.
Use a switch when you only need to detect presence or absence—for example:
  • High or low-level alarms in silos, hoppers, bins, or chutes
  • Pump protection (inlet starvation or overflow prevention)
  • Flow/no-flow indication in conveyors or chutes
  • Plugged chute or blocked pipe detection
Switches are simpler, lower-cost, and more rugged than continuous measurement systems, requiring no calibration drift correction and minimal maintenance.
Sonac 220

Sonac 220

For terminal operators, plant engineers, maintenance teams, and EPC specifiers who need precise high- or low-level alarms or plugged-chute detection in difficult liquids or bulk solids without intrusion into the process.

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Why Use an Ultrasonic Switch

Choose an ultrasonic switch when you need non-contact, through-air detection in challenging process conditions:

No Contact With Material: Avoids wear, coating, or buildup—ideal for sticky, abrasive, or corrosive solids.

Works in Dusty or Steamy Conditions: Ultrasonic energy is unaffected by opacity or color.

Gentle on Fragile Materials: Detects powders or flakes that could be damaged by mechanical probes.

Handles Very Low Bulk Densities: Reliably senses materials as light as ¼ lb/ft³.

Fail-Safe and Self-Checking: Internal self-test ensures proper operation and alarms on any component failure.

Simple Setup and Calibration: Adjustable delays (50 ms–30 s) and field-selectable fail-safe logic.

Switch Comparison Table

Attribute Sonac 110 (Magnetostrictive Liquid Switch) Sonac 220 (Ultrasonic Bulk/Solids Switch) Microwave 320 (Non-Contact Microwave Switch)
Measurement Principle
Magnetostrictive resonant damping sensor with diaphragm and pickup coil
Ultrasonic acoustic feedback between matched transmitter/receiver sensors (≈38 kHz)
Pulsed X-band microwave (10.525 GHz) transmitter/receiver pair with pulse discrimination
Type
Contact
Contact (non-intrusive for solids; sensors face each other)
Non-contact
Primary Media
Liquids only (crude, refined products, solvents)
Solids, granular materials, fragile products, opaque or transparent objects (≥¼ lb/ft³)
Liquids or solids; detects through non-metallic windows; requires window for metal tanks
Typical Applications
Overflow alarm, high/low liquid level, small vessels/pipes
Bulk solids level, position detection, plugged chute, fragile materials
External level detection, aggressive/hot products, bins/chutes/tanks
Fail-Safe Capability
Self-testing circuit triggers relay on failure
Internal self-test (new PCB)
Selectable fail-safe (high/low)
Operating Temp – Electronics
-40 to 160 °F
Nylon sensor: 220 °F; Ryton: 400 °F
–40 to 160 °F
Operating Temp – Sensor/Process
Liquid-contact diaphragm; temp defined by sensor build
Up to 400 °F for Ryton sensor
Up to 750 °F with high-temperature weldments/sensors
Pressure Rating
Up to 2,000 psig maximum
Not pressure-rated (ambient solids/air-gap use)
Weldment/window dependent; microwave head itself not pressure-rated
Output Type
SPDT relay
Relay output
DPDT relay (5 A @120 VAC; 3 A @240 VAC/24 VDC)
Power Requirements
4-wire electronic switch
AC/DC depending on configuration
115 VAC, 24 VDC, or 230 VAC; 6 VA
Intrusion Into Process
Minimal (<¼″ probe tip)
Non-intrusive to solids (air-gap)
No intrusion
Calibration
Gain + time delay adjustments
Gain + strap adjustments
Gain, time delay, gain select
Signal Path Sensitivities
Damped by liquid contact
Affected by humidity/temperature (auto-adjust frequency)
Response varies with dielectric constant & conductivity
Maintenance
No moving parts; periodic function check
Clean sensors; verify alignment
Align windows; keep path clear
Not Recommended For
Solids, powders, aerated slurries
Heavy slurries/high-viscosity liquids
Direct immersion in liquids

Why Use the Sonac 220 With Other Technologies

Use the Sonac 220 instead of another L&J switch when you need:

  • Non-contact operation (no sensor intrusion or contamination risk)
  • Reliable solid and powder detection across distances up to 12 ft (3.6 m)
  • Fail-safe performance in dusty, vibrating, or abrasive environments
  • High-temperature compatibility (Ryton or stainless-steel sensors rated to 400 °F)
  • Compact, corrosion-resistant design (NEMA 4X enclosure, DPDT relay outputs)
  • Simple installation and self-test verification

Typical Applications

  • Bulk powder storage bins and hoppers
  • Light, fluffy, or aerated materials (plastics, wood chips, cereal grains)
  • Plugged-chute detection in conveyors and feeders
  • Recycle, cement, or aggregate systems
  • Food, pharmaceutical, and sanitary packaging lines (with 304 SS coupling option)

Summary

The Sonac 220 bridges the gap between mechanical contact switches and long-range microwave barriers.
It offers precise, fail-safe, non-contact control for bulk solids in industries where reliability and cleanliness are critical—cement, food, chemical, pharmaceutical, and plastics alike.