Ultrasonic Digital Thickness Gauge, General Purpose, Model 4 by Cygnus

Measures metal thickness to determine wastage or corrosion accurately, quickly and without removing protective coatings.
  • Light, rugged, small and shock-proof within IP65 & IP67 sealed aluminum 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 backlight
  • 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 (3/4") thick
  • Rugged probe cable designed for superior flexibility.
The new Cygnus 4 is the most versatile through coating thickness gauge available and perfect for all lighting conditions.

Lighter and simpler to use, yet accurate and very durable!

Ideal for use on flat surfaces or pipes. Our multiple echo single crystal probe technology means you can measure through thick coatings and only the remaining metal thickness is displayed.

  • Measures remaining metal thickness on corroded and coated structures
  • All measurements are error checked using 3 return echoes to give repeatable, reliable results
  • Accepted by all major classification societies
  • Greatly reduces inspection time and costs
  • Echo strength indicator to aid measurement.

With multiple echo, readings are taken by measuring the time delay between any three consecutive backwall echos. The time of T1 (coating thickness) is ignored. The times of T2 and T3 are equal to the time that it takes to travel through the metal. Only by looking at three echoes can the measurements be automatically verified (where T2 = T3).

Kit Contents
  • Instrument
  • Remote, 2.25 MHz, 13 mm (1/2") diameter probe
  • Spare membranes
  • Steel test block
  • Membrane couplant
  • Ultrasonic couplant
  • Accessory pouch
  • Protective silicone sleeve w/ belt/harness clip
  • Neck strap
  • Operation Manual
  • Blue high flex probe cable and case.




Maintenance and safety checks of metal thickness for:

  • Ships
  • Storage tanks
  • Pipelines
  • Bridges
  • Street lighting columns
  • LPG vessels
  • Road transport tankers
  • Offshore platforms
  • Piers, jetties and pilings
  • Processing vessels
  • Cranes.

...plus many more.




Sound velocities between 2000 and 7000 m/s (0.059 and 0.31 in/microsec)

Covers virtually all common engineering materials

Measurement Range in Steel

3 mm - 250 mm (0.100" - 9.995") with 2.25 MHz probe

2 mm - 150 mm (0.065" - 6.000") with 3.5 MHz probe

1 mm - 50 mm (0.045" - 4.000") with 5.0 MHz probe


0.1 mm (0.005") when calibrated in accordance with Cygnus Instruments Calibration Procedures


0.1 mm or 0.05 mm (0.005" or 0.002") (selectable)


Single-crystal, soft-faced compression.
6 mm (1/4")  - 5 MHz
13 mm (1/2") - 2.25 MHz, 3.5 MHz or 5 MHz
19 mm (3/4") - 2.25 MHz

(Lower frequency probes offer better penetration on heavy corrosion/coatings)

Power source

2 x AA alkaline batteries or rechargeable NiMH / NiCd

Battery life

30 hours continuous operation with alkaline batteries


Large liquid crystal display with white backlight - automatically turns off in bright light conditions


85 mm x 115 mm x 25 mm (3 3/8" x 3 1/2" x 1")


275 g (9.7 oz) (inc. batteries)


CE, British Standard BS EN 15317:2007

(Specification for the characterisation and verification of ultrasonic thickness measuring equipment

Environmental Protection

IP65 & IP67

Operating Temperature

-10°C to +50°C (14°F to 122°F)


RoHS, WEEE compliant


3 years on gauge, 6 months on probe

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

Cygnus Multiple Echo Technology

With multiple echo technology, readings are taken by measuring the time delay between any three consecutive backwall echoes. The time T1 (for coating thickness) is ignored. The times T2 and T3 are equal to the time that it takes for sound to travel through the metal. Only by looking at three echoes can the measurements be made for the metal thickness, where T2 = T3.