Cygnus Instruments

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The Cygnus 4 General Purpose is a compact, light-weight, general purpose digital thickness gauge from Cygnus Instruments.

This hand-held NDT ultrasonic thickness gauge measures metal thickness and corrosion levels providing accurate, error-checked measurements through coatings. Highly versatile it can be employed in most hand-held industrial or shipping inspection applications.

The LCD display is easily visible outdoors and its automatic white back light control makes it ideal for use in all light conditions. Menu-driven operation and "Deep-Coat" mode allow easy thickness gauging through coatings up to 20 mm.

Cygnus 4, supplied in an IP65 & IP67 rated/sealed aluminium enclosure, protective silicon sleeve and optional belt/harness clip is extremely light, tough and simple to use.

Supporting Information

Please view the IACS document covering requirements for ultrasonic thickness measurement in Shipping.

Also, please view the Weathering Steel for Highway Structures - Residual Steel Thickness Measurement Using Ultrasonic Gauges document.

It is vital to use the right probe for the optimum performance of thickness gauges. Learn how to select the right probe.

Cygnus 4 General Purpose Brochure

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Cygnus 4 General Purpose
  • Cygnus 4 General Purpose Thickness Gauge
  • Cygnus 4 General Purpose Kit


The Cygnus 4 General Purpose operating manual can be download from Support Downloads.


  • Light, rugged, small and shock-proof within IP65 & IP67 sealed aluminium enclosure
  • Gauge senses probe type and automatically adjusts settings for optimum performance
  • Valid thickness measurements and minimum thickness function
  • LCD Graphic Display with automatic white back light
  • Cygnus Echo-Strength bars assist thickness measurements
  • Simple gauge and menu operation with 3 tactile keys
  • Protective silicone sleeve offers maximum protection and versatility
  • Secure, Twist-to-lock probe connection (BNC)
  • Deep-coat mode for coatings up to 20 mm thick
  • Display Freeze function for easy measurement verification and logging.

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Materials Sound velocities between 2000 m/s and 7000 m/s - covers virtually all common engineering materials
Measurement Range in Steel 3 mm - 250 mm with 2.25 MHz probe
2 mm - 150 mm with 3.5 MHz probe
1 mm - 50 mm with 5 MHz probe
Accuracy 0.1 mm when calibrated in accordance with Cygnus Instruments calibration procedures
Resolution 0.1 mm or 0.05 mm (selectable)
Probes Single crystal soft-faced compression
6 mm - 5 MHz
13 mm - 2.25, 3.5 or 5 MHz
19 mm - 2.25 MHz
Power 2 x 'AA' alkaline batteries or rechargeable NiMH / NiCD
Battery Life Up to 30 hours' continuous operation with alkaline batteries
Display Large liquid crystal display with white backlight - automatically turns off in bright light conditions
Size 85 mm x 115 mm x 25 mm
Weight 275 g (including batteries)
Operating Temp -10 °C to +50 °C
Environmental Protection IP65 & IP67
Compliance CE, British Standard BS EN 15317:2013
Environmental RoHS, WEEE compliant

Kit Content

Instrument, 2.25 MHz 13 mm diameter probe, spare membranes, 15 mm steel test block, membrane couplant, ultrasonic couplant, accessory pouch, protective silicone sleeve with neck strap, operation manual, carry case and optional belt/harness clip.






  • Corrosion checks on ships' shell plates, bulkheads and structures
  • Maintenance and safety checks on bridges and street lighting columns
  • Metal thickness monitoring on cranes, marine structures and conveying systems
  • Metal thickness safety checks on steam and pressurised water systems, transportable gas containers and compressed air systems
  • Quality assurance metal thickness checks
  • Systematic wall thickness and corrosion monitoring of storage tanks, process vessels and road tankers.

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