Microwave Switches

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Non-Contact Point Level Detection for Harsh or Challenging Applications

Microwave point level switches provide highly reliable on/off detection using a completely non-contact sensing method. Instead of relying on floats or mechanical movement, a microwave switch uses a paired transmitter and receiver mounted across a tank, chute, or vessel. The transmitter emits a focused, pulsed microwave beam; as long as the material has not reached the detection point, the receiver sees a strong, uninterrupted signal. When liquid or solid material enters the beam path, it absorbs or blocks the microwave energy, causing the received signal to drop and triggering an immediate level alarm or control action.

Because the sensors do not touch the process, microwave switches excel in applications that involve extreme temperatures, corrosive or abrasive materials, heavy buildup, or high-velocity flow—conditions that often damage or overwhelm mechanical point switches. They work through non-metallic tank walls or dedicated microwave windows, and are especially useful in bins, hoppers, chutes, and vessels where solids or sticky products make other technologies unreliable.

Installation Is Straightforward: Mount the transmitter and receiver on opposite sides of the vessel, align their beams, and connect the control unit. With adjustable gain, selectable fail-safe modes, and flexible time-delay settings, microwave switches can be tuned precisely to the process. Once set up, they require minimal maintenance and remain stable over long operating periods.

Cognesense microwave switches are based on our proven technology platform and deliver robust performance through solid-state electronics, wide operating temperature ranges, optional water cooling for extreme temperatures, and reliable operation in dusty, hot, or corrosive environments. Their non-contact design and strong signal discrimination make them the switch of choice when plant operators need dependable, nuisance-free point level detection in the most demanding service conditions.

Microwave 320 — Non-Contact Microwave Barrier Switch

For plant operators, process engineers, maintenance teams, and EPCs who need reliable on/off detection in tough solids or vapor-laden services, the microwave switches provide non-contact “across-the-gap” point level detection that sees through dust and steam and avoids intrusive hardware. Unlike contact probes that foul or wear, the Microwave 320 mounts outside the flow (or behind a window) and tolerates abrasion and high temperatures with rugged heads, windows, waveguides, and optional cooling kits.
Ideal for: blocked-chute alarms, high/low silo trip, belt load/plug detection, flow/no-flow confirmation, object presence in high temperature conditions where normal sensors are damaged or buildup on the sensor will damage functionality over time.

Why Use a Switch Vs a Level Gauge?

  • Switch (Point Level = on/off): Best when you need a discrete action—start/stop a conveyor, trip a high-level alarm, stop a feeder, detect a blockage. Lower installed cost, simpler wiring, easier to maintain.
  • Level Gauge (Continuous): Choose a gauge when you need inventory/trending/custody or continuous control (e.g., maintain setpoint, report tank volume). Radar, ultrasonic, hydrostatic, or servo provide a 4–20 mA/fieldbus measurement with history.
Rule of thumb: If the control decision is binary (trip/no trip), use a switch. If you need a trend or number, use a gauge. Use both for redundant, safe operations in your applications.
Sonac 220

Microwave 320

For process engineers, maintenance planners, safety officers, and plant managers who need reliable level detection across bulk solids, powders, or liquids…

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Why Use a Microwave Switch?

Use a microwave switch when:

You need non-contact detection across a gap. A transmitter and receiver face each other across a chute, belt, or outlet. No probe in the material stream.

Dust/steam/abrasion/high heat are present. Microwaves penetrate dust and vapor; with windows/waveguides (and optional cooling) the hardware stays protected.

You must avoid vessel penetration. Install behind glass/ceramic/PTFE windows to keep hygiene and pressure boundaries intact.

Simple, robust control is preferred. Binary relay outputs with selectable fail-safe and on/off delays; long cable runs are straightforward.

When to Use Microwave and Another Technology Together

  • You need continuous level/inventory. Use radar/ultrasonic/hydrostatic/servo gauges for level and the microwave switch for controls.
  • No line-of-sight or no room for a receiver. For very short spans or tight geometries, consider vibrating fork, capacitance (Captrol/Cap-Analog), or rotary paddle.
  • All-metal vessel with no microwave window. Either add a non-metallic window or use an intrusive technology (vibrating fork, capacitance, displacer/float).
  • Spec mandates native plant comms/diagnostics over long spans. Consider feature-rich platforms (e.g., Ethernet/Modbus barrier systems) or add a small I/O module at the panel with the Microwave 320.

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

Quick Selection Guide

Yes: a switch is right.

  • Yes: Microwave 320.
  • No: consider Sonac 110/220 (compact probe) or Captrol (capacitive) with your level gauges.

Yes: Microwave 320 with window/waveguide; add cooling if needed.

Use a level gauge (radar/ultrasonic/hydrostatic) or add a small I/O module for comms.

Applications

  • Bulk Solids: blocked chute, crusher/breaker plug, conveyor load/edge, silo high/low.
  • Power/Cement/Mining: kiln feed, clinker/baghouse, coal handling.
  • Agri/foods: grain elevators, flour/sugar dust.
  • Chemicals: powders/pellets, pneumatic conveying.
  • Waste & Biomass: RDF/wood chips, sludge cake transfer.

Benefits

  • Non-contact, No intrusion into process; installs behind a window.
  • Accessory Depth (windows, waveguides, cooling) for severe service.
  • Dust-hazard Packages and North-America-centric approvals.
  • AC/DC Power with DPDT relay and simple fail-safe logic.
  • Long cable runs for retrofit flexibility.

Specs at a Glance (Microwave 320)

  • Operating principle: Pulsed Microwave Barrier, ~10 GHz (X-band)
  • Outputs: DPDT relay, Selectable fail-safe, On/off delay timers
  • Power: 115/230 VAC or 24 VDC
  • Install distance: Model-dependent span; Supports long head-to-control cabling
  • Options: Non-metallic windows, Waveguides, Water-cooled heads, Rugged pipe housings with UHMW window
  • Approvals: Packages available for dust hazardous areas (E/F/G)

FAQs

No. It can operate through non-metallic windows (glass/ceramic/PTFE). Use window kits for sealed vessels.

Consider a probe-style switch when a Tx/Rx pair won’t fit.

Microwave 320 focuses on rugged detection with relay outputs. If you need plant-wide comms, either add a small I/O module at the panel or evaluate feature-rich barrier systems.