Dakota NDT probes and accessories — the eight families
Transducers — dual element
Transducers for corrosion thickness gauges
Twin-crystal probes for measuring remaining wall thickness on corroded materials and irregular surfaces, where separating the two crystals eliminates ring-down.
- Frequencies 1, 2.25, 5, 7.5 and 10 MHz
- Diameters from 3/16″ up to 1″
- Standard, high or ThruPaint damping
- Temperature from ambient up to 500 °C
- Compatible with the CX, ZX, CMX, MX and CMX10-DL series
Transducers — single element
Transducers for precision thickness gauges
Single-crystal, delay line and contact probes for high-resolution measurements on metals, plastics, glass and thin materials.
- Frequencies 2.25, 5, 10, 15, 20 and 25 MHz
- Contact, delay line and pencil types
- Diameters from 1/8″ up to 3/4″
- Resolution down to 0.001 mm, thicknesses from 0.127 mm in plastic
- Microdot and LEMO 00 connectors; compatible with PMX, PCX8-DL and the BT series
Transducers — flaw detectors
Transducers for ultrasonic flaw detectors
Quick-change and standard shear wave probes, single element contact probes and angle wedges for the inspection of welds, forgings and composites.
- Wedge angles 45°, 60°, 70°
- Frequencies 2, 4 and 5 MHz
- Quick-change system and standard screw fixing
- Compatible with FX70-DL, FX71-DL and FX81-DL; TRIG and DAC modes
- For inspections to AWS D1.1, EN ISO 17640 and ASME
Transducers — bolt tension
Transducers for bolt tension monitors
Probes dedicated to the ultrasonic measurement of the elastic elongation of threaded fasteners, to calculate the clamping load non-destructively.
- Frequencies 2, 5, 10 and 20 MHz
- Contact, magnetic and click-on types
- Compact diameters for seating on the bolt head
- Compatible with BT1-DL and BT2-DL
- Specific calibration for each fastener
Accessories — probe cables
Cables for ultrasonic transducers
Genuine cables that guarantee signal integrity and connector compatibility with every Dakota instrument.
- LEMO 00, BNC, Microdot and ODU Smart Port connectors
- Lengths from 1 to 10 metres
- Double or triple shielding for EMI immunity
- Straight and right-angle configurations
- Industrial PVC and polyurethane jackets
Accessories — calibration
Calibration blocks for ultrasonic thickness gauges
Certified references for daily calibration: without a reference block the instrument’s stated accuracy cannot be guaranteed.
- Certified AISI 4340 steel material
- Tolerance ±1% of the nominal value
- Step blocks and single blocks, rectangular and stepped shapes
- Thicknesses from 1 mm to over 50 mm
- Calibration certificate included with every block
Accessories — delay line tips
Delay line tips for precision transducers
Interchangeable tips that delay the surface echo, making thickness measurement possible on very thin materials.
- Acrylic and graphite materials
- Standard 1/4″ and 3/8″ diameters
- Acrylic for metals and rigid materials, graphite for thin plastics and rubber
- Interface-Echo, Echo-Echo and Plastic modes
- Quick replacement without changing the probe
Accessories — couplants
Ultrasonic couplants
The physical bridge between probe and material: without couplant, air reflects almost the entire signal and measurement is impossible.
- Standard formulation from -15 to 104 °C
- High-temperature formulation up to 398 °C
- Viscosity tuned for horizontal and vertical use
- Non-corrosive, non-toxic composition
- Supplied in tubes and canisters
The ultrasonic probe (or transducer) is the most critical component of any NDT measurement system: it is the physical interface between the instrument and the material under inspection, and the quality of the results depends on choosing the right probe just as much as on the instrument itself. Dakota NDT manufactures a wide range of probes — from the most common dual element probes for corrosion measurement through to specialist high-temperature, delay line, micro-point and angle beam probes for weld inspection. This page presents the main families of Dakota probes to help you find your way through the choice. For the specific configuration suited to your instrument and your application, our technical team is at your disposal.
The three main families of ultrasonic probes
In terms of construction, ultrasonic probes fall into three broad categories, each optimised for a type of application:
Dual Element Probes
Dual element probes have two separate piezoelectric crystals — one transmits, the other receives. This physical separation eliminates “ring-down” (transmitter noise), allowing measurements on reduced thicknesses and on corroded or irregular surfaces. They are the standard choice for corrosion measurement and form the largest family in the Dakota catalogue.
- Typical frequency: 1-10 MHz (2 and 5 MHz most common)
- Compatible instruments: all CX, ZX, CMX, MX and CMX10-DL series; R9 and RX8-DL motorsport; thickness mode on FX flaw detectors
- Typical range: from 0.6 mm up to over 900 mm in PE mode (depending on probe and material)
Examples of Dakota dual element probes
CTX-501
5 MHz, 11.1 mm diameter: general-purpose probe for steel, typical range 1-150 mm. The most widely used probe in the catalogue.
CTX-561
5 MHz, 15 mm diameter: extended range for thicker materials, up to over 200 mm.
CTX-281
2 MHz: for attenuating materials such as grey cast iron, ductile iron and alloy steels.
CTX-1021
10 MHz: high resolution for thin sections.
CTX-502HT
5 MHz high temperature, up to 500 °C, with dedicated couplants.
CTX-5001R
5 MHz micro-point for restricted access and tight radii of curvature.
CTX-1901
Delay line for very thin sections.
Need help choosing the right product?
Single Element Probes
Single element probes have a single crystal that transmits and receives alternately. They offer higher spatial resolution than dual element probes (useful on thin sections) and generally higher frequencies. They are the choice for precision measurement and for flaw inspection with normal-beam probes.
- Typical frequency: 1-25 MHz (5, 10, 15 and 20 MHz most common)
- Compatible instruments: PMX series (PMX2-DL, PMX3-DL, PMX4-DL), PCX8-DL, BT1-DL and BT2-DL bolt tension, FX70-DL / FX81-DL flaw detectors, CMX10-DL (in addition to dual element)
Types of single element probe
Contact probe
In direct contact with the material, for general applications.
Delay line probe
With a delay line: they move the surface echo further out in time, allowing accurate measurement on very thin sections, from 0.127 mm on plastic.
Pencil probe with delay tip
Pencil probes for restricted access and small components.
High-frequency probes
15-25 MHz: maximum resolution for packaging, film and aerospace components.
Examples of Dakota single element probes
TXC15M0CM
15 MHz, supplied as standard with the PCX8-DL for thin substrates.
TXC10M0CM
10 MHz single element contact.
TXC20M0CM
20 MHz, ultra-high resolution for film and packaging.
Delay line 1/4″
1/4″ delay line probes with 3/8″ and 1/2″ delay tips: standard kit for PMX2-DL and PMX3-DL.
Angle Beam Probes
Angle beam probes are single element probes coupled to a plastic wedge that deflects the ultrasonic beam at a preset angle to the surface normal. They are the family dedicated to weld inspection to AWS D1.1, EN ISO 17640 and ASME Sec. V.
- Standard angles: 45°, 60°, 70° (measured in steel)
- Typical frequencies: 2, 4, 5 MHz
- Compatible instruments: FX70-DL / FX71-DL and FX81-DL flaw detectors; CMX10-DL with the Angular (prove-up) function
- Required detection modes: TRIG (Trigonometric) for 2D location, DAC for flaw classification
Dakota angle beam probes include the wedge integrated into the probe assembly — the refraction angle in steel is guaranteed by the optimised wedge design. For specialist inspections, interchangeable wedges are available to suit curved surfaces (pipework of a specific diameter) or materials with different sound velocities.
How to choose the right probe: decision criteria
Selecting the optimum probe depends on five main factors:
1. Material to be measured
- Carbon steels, common stainless steels: 5 MHz dual element probes (CTX-501) — the universal choice
- Aluminium, light alloys: 5-10 MHz dual element
- Grey cast iron, ductile iron: 2 MHz (CTX-281) — the low frequency compensates for grain attenuation
- Highly attenuating austenitic steels: 2 MHz or specialist low-frequency probes
- Thick plastics, rubber, composites: low-frequency probes (500 kHz – 2 MHz) for the PMX4-DL
- Glass: 5-10 MHz
2. Expected thickness range
- < 1 mm: high-frequency (10-25 MHz) single element delay line probes
- 1 – 50 mm: standard 5 MHz dual element (CTX-501)
- 50 – 200 mm: 5 MHz dual element, larger diameter (CTX-561)
- > 200 mm: low frequency (1-2 MHz) with a large-diameter element
- Up to 1400+ mm: CMX10-DL only, with dedicated probes
3. Operating temperature
- Ambient: standard probes
- High temperature (up to 500 °C): HT probes such as the CTX-502HT, with a specific couplant
- Below zero: check the probe specifications — most work down to -20/-30 °C
4. Physical access
- Accessible flat surfaces: standard probe
- Restricted areas, tight curvatures: micro-point probes such as the CTX-5001R
- Curved surfaces (tubes, small vessels): assess the element diameter in relation to the radius of curvature
5. Instrument in use
- The ZX series supports only 1-10 MHz dual element probes
- The PMX series requires 1-25 MHz single element probes
- The PMX4-DL High Penetration is optimised for 500 kHz – 10 MHz probes (lower frequencies than the standard PMX)
- The CMX10-DL supports dual, single, delay line and angle beam probes with automatic ODU recognition
- The BT1/BT2 bolt tension instruments require dedicated bolt tension probes
Further reading: How to choose the right ultrasonic transducer for each application — a complete technical guide from our blog.
Available accessories
In addition to probes, Dakota supplies the complete set of accessories for each instrument:
Ultrasonic couplants
In various formats: standard, high temperature, low temperature and for food-grade applications.
Calibration blocks
Step blocks in steel, aluminium and specific alloys.
Probe cables
LEMO-00, Microdot, BNC and ODU Smart Port, in various lengths.
Batteries and Li-Ion packs
Rechargeable battery packs.
Carrying cases
Hard cases.
Screen protectors
For touchscreen models.
Hand and wrist straps
Wrist harnesses and hand straps.
Power supplies and adapters
In UK, EU and US formats.
USB cables
Standard and USB-C.
Why probe selection is critical
A probe unsuited to the application can produce:
Unstable or inconsistent readings
Probe frequency too low on a homogeneous material, or vice versa.
Inability to detect the back-wall
Probe frequency too high on an attenuating material.
Systematic errors
Improper coupling: dual element probe on excessively corroded surfaces.
Slow or non-repeatable measurements
Probe geometry unsuited to the surface.
Probe damage
Standard probe used at high temperature without a dedicated couplant.
Not sure which probe you need?
Tell us the material, thickness range, operating temperature and the model of the instrument you own: we will propose the right probe and accessories. Contact us for dedicated technical advice.
Further information and contacts
Systems division and sensor integration partner : www.roder.it
More information about RODER SRL : about us
Contact for general information : info@roder.it
Contact for information about these products : info@roder.it
The information contained on this web page is provided for information purposes only. Although it has been compiled with the utmost care, it does not constitute a contractual offer or a binding commitment to supply. It may contain transcription, translation or typographical errors. For precise and up-to-date information, please contact our company directly.
Some images on this website have been intentionally generated using Artificial Intelligence (AI). This is because, for many applications and projects, it is not possible to disclose photographs of the installation or of the actual system due to confidentiality agreements, confidentiality clauses and non-disclosure agreements (NDAs).