Dakota CX4 – Thickness Gauge with ThruPaint™

The Dakota CX4 is the mid-range model of the Dakota NDT CX series: it keeps the operating simplicity of the CX2 while adding the essential functions for those who must measure through coatings (paints, galvanising, epoxies) and work on materials with variable sound velocity. It is the ideal instrument for industrial maintenance of painted lines, inspection of pipework with protective coating and quality control on materials other than standard steel alone.

Positioning within the Dakota CX range

The CX4 sits between the CX2 (basic, Pulse-Echo only) and the CX8-DL (with data logger). Compared with the CX2 it adds three key functions:

• Echo-Echo ThruPaint™ (EE) mode to measure the metal thickness while ignoring coatings up to 2 mm (80 mils)
• Velocity Mode (VM) to determine the sound velocity on a part of known thickness
• HD dual element probe (High Definition), to be ordered separately, with superior performance on corroded or uneven surfaces

It keeps the same hardware structure as the rest of the series: 2.4″ colour TFT display, IP64 housing, compliance with ASTM E797, EN 14127 and EN 15317, calibration traceable to NIST and MIL-STD-45662.

When to choose the Dakota CX4

• Inspections on painted or coated surfaces up to 2 mm (industrial paints, epoxies, hot-dip galvanising, antifouling)
• Maintenance of pipelines and tanks with external protective coatings without the need for preliminary blasting
• Galvanised structural steelwork: pylons, towers, metal supports
• Users working on different materials who need to characterise non-standard sound velocities
• Inspections under plate, under primer and under finish in marine and offshore applications
• Quality control on materials of variable composition (castings, forgings)

If you need electronic storage of measurements and B-Scan, consider the Dakota CX8-DL. If you also need to inspect the A-Scan waveform (for attenuating materials or defect verification), the choice is the CMX series.

Main features

The three measurement modes

• Pulse-Echo (PE): standard mode, range 0.63 – 500 mm (0.025 – 19.999″)
• Echo-Echo ThruPaint™ (EE): ignores coatings up to 2 mm, range 2.54 – 20.00 mm (0.100 – 0.787″)
• Velocity Mode (VM): determines the sound velocity between 1,250 – 10,000 m/s (0.0492 – 0.3937 in/µs)

Full technical specifications

Measuring mode	PE, Echo-Echo ThruPaint™ (EE), Velocity Mode (VM)
PE range	0.63 – 500 mm (0.025 – 19.999″)
EE range	2.54 – 20.00 mm (0.100 – 0.787″)
VM range	1,250 – 10,000 m/s (0.0492 – 0.3937 in/μs)
PE accuracy	±0.1 mm (0.63-19.99 mm); ±0.5% (20-500 mm)
EE accuracy	±0.1 mm (2.54-25.4 mm)
Measurement rate	4 Hz
Resolution	0.1 mm (0.01″)
Unit	mm or inches
Display	2.4″ colour TFT, backlit, resistant to scratches and solvents
Calibration	Zero, 1 point, material (39 preset), factory reset
Data Logger	Not available (see CX8-DL)
Protection	IP64
Operating temperature	-10 to 50 °C
Power supply	2 AA batteries (or USB from PC)
Battery life	15 hours (alkaline) / 28 hours (lithium)
Weight	210 g with batteries, without probe
Dimensions	145 × 73 × 37 mm
Firmware updates	Via DakMaster™
Warranty	2 years
Standards	ASTM E797, EN 14127, EN 15317
Calibration	Traceable to NIST and MIL-STD-45662

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Echo-Echo ThruPaint™ mode

It is the distinguishing function of the CX4 compared with the CX2. The instrument analyses two consecutive echoes coming from the back wall of the material: since both have passed through the same coating, this is mathematically eliminated from the calculation. The result is the pure metal thickness, independent of the surface coating.

The technical limit is 2 mm of coating (80 mils): beyond this value the attenuation of the multiple echoes becomes too significant. This mode is compatible with:

• Acrylic, polyurethane and epoxy industrial paints
• Hot dip galvanising
• Protective enamels
• Marine antifouling coatings
• Primers and multi-layer finishes within the combined limit of 2 mm

For more on the technique, see the guide Echo-Echo and ThruPaint™: measuring thickness through coatings.

Typical applications

Inspection of painted pipelines and pipework

The CX4’s ThruPaint™ mode is ideal for periodic thickness checks on process pipework with external anti-corrosion coatings. The inspection is carried out without removing the paint, preserving the integrity of the cathodic protection. For detailed procedures under API 570, see the guide Corrosion inspection on in-service pipework.

Checking the shells of coated tanks

For spot inspections on atmospheric tanks with external painted protection, the CX4 provides reliable readings of the metal thickness. For intensive mapping under API 653, the CX8-DL with structured data logger is preferable; see Thickness checks on storage tanks according to API 653.

Galvanised steelwork and pylons

Hot-dip galvanised structures have a protective coating typically between 85 and 150 µm. The CX4 with ThruPaint™ measures the thickness of sheets and profiles directly without removing the galvanising, preserving the anti-corrosion protection.

Sound velocity characterisation

Velocity Mode is valuable in contexts such as:

• Receiving castings and forgings with variability of composition between batches
• Checking cast irons and special alloys with non-standard velocities
• Verifying the metallurgical consistency of semi-finished products
• Preparing custom calibration blocks

General industrial maintenance

The CX4 is a versatile instrument for industrial maintenance teams that have to work on multiple assets: machinery, pipework, structures, supports. For applications on difficult materials (cast iron, composites, thick plastics), consider the PMX4-DL or the CMX series with A-Scan.

CX2 / CX4 / CX8-DL comparison

Feature	CX2	CX4	CX8-DL
Pulse-Echo (PE)	✓	✓	✓
Echo-Echo ThruPaint™	—	✓	✓
Velocity Mode	—	✓	✓
HD probe required for Echo-Echo	—	✓	✓
Scan Mode	—	—	16 Hz
B-Scan	—	—	✓
Data logger	—	—	100,000 readings

For a detailed analysis see Dakota CX2 vs CX4 vs CX8-DL: which thickness gauge to choose?.

Scope of supply

• Dakota CX4 gauge
• 5 MHz ⅜” HD right angle dual element transducer (TXC5M00CP-10)
• Ultrasonic couplant gel
• Carry pouch
• Screen protector
• Wrist harness
• 2 AA batteries
• User manual
• Test certificate

For more on choosing the probe: probes for corrosion thickness gauges and the guide How to choose the right ultrasonic transducer. For a quotation, please state the order code and quantity.

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Documentation download

Official Dakota NDT technical documentation. Files open in a new tab.

	CX series datasheet (CX2 / CX4 / CX6-DL / CX8-DL)	Datasheet
	Multilingual user guide CX2 and CX4 (8 languages)	Guide
	CE Declaration of Conformity — CX2 / CX4	CE conformity
	UKCA Declaration of Conformity — CX2 / CX4	UKCA conformity

Hardware and interface

• 2.4″ (6 cm) colour TFT display with permanent backlight and ambient sensor
• Display resistant to scratches and solvents
• Large buttons with positive tactile feedback, also suitable for use with gloves
• IP64 protection rating: resistant to impact, water and dust
• Multilingual menu structure
• USB power supply via PC available

Accuracy and precision

• PE accuracy: ±0.1 mm (0.63-19.99 mm); ±0.5% (20-500 mm)
• EE accuracy: ±0.1 mm (2.54-25.4 mm)
• Selectable resolution: 0.1 mm (0.01″)
• Reading rate: 4 Hz
• Repeatability and stability indicator to validate the quality of the measurement
• Automatic probe recognition: automatic check of the correct transducer connected
• Auto V-path correction for dual element probes

Calibration

• Integrated Zero on the instrument’s reference disc
• 1-point calibration for quick offset correction
• Calibration on known velocity (speed of sound)
• Calibration on known thickness with automatic velocity determination (Velocity Mode)
• 39 preset materials in the internal database

Standards and certifications

• ASTM E797: Standard Practice for Measuring Thickness by Manual Ultrasonic Pulse-Echo Contact Method
• EN 14127: Non-destructive testing – Ultrasonic thickness measurement
• EN 15317: Characterisation and verification of ultrasonic thickness measuring equipment
• Factory calibration traceable to NIST and MIL-STD-45662A
• CE Declaration of Conformity (Europe)
• UKCA Declaration of Conformity (United Kingdom)

Frequently asked questions

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For quotations, field demonstrations or a comparative assessment with other Dakota models, contact our technical office.