The questions our technical office receives most often, gathered in one place: instrument choice, probes, calibration, readings that do not add up, standards and services.
- ✓ Choosing the instrument: what really changes between models
- ✓ Measuring through paint: when it is needed and which models do it
- ✓ Probes: how to choose frequency and type
- ✓ Unstable readings: the most common causes
- ✓ Calibration: how often and with which certificate
- ✓ Standards: what they require of the instrumentation
Whoever calls our technical office rarely has a theoretical question. They have an instrument in hand that does not read as it should, a tender to prepare, an auditor on the way or a purchasing decision to justify to whoever signs. The answers below are the ones we give on the phone, written as we would say them.
Where the answer needs more than a few lines you will find a link to the guide that goes deeper. If your question is not here, write to us: in most cases it is solved remotely at the first contact, and we add it to this page.
Need help choosing the right product?
For the meaning of the technical terms that recur in the answers — A-Scan, Echo-Echo, PECT, V-path, data logger — see the Glossary of technical terms.
Choosing the instrument
The field of use and the type of probe. A corrosion gauge uses dual element probes and is optimised for thick, irregular walls, with a resolution of one hundredth of a millimetre: it serves to know how much material is left. A precision gauge uses single element, delay line and pencil probes, goes down to a thousandth and has Interface-Echo modes: it serves to verify that a machined part meets tolerance.
The A-Scan shows the waveform instead of just the number, and lets you check where the gate has locked onto the echo. On clean, regular surfaces you can do without it; on advanced corrosion, irregular back walls or attenuating materials it is often the only way to understand whether an anomalous reading is real or an artefact.
It indicates the presence of the data logger, i.e. the ability to store readings in the instrument and then transfer them to the computer. Models without DL show the measurement but do not keep it: they are fine for occasional checks, not for campaigns to be documented.
Yes, but an instrument with Echo-Echo or PECT mode is needed: not all models have it. In the Dakota range it is offered by the ZX6-DL, the CMX series and the CX models with ThruPaint. Pulse-Echo-only instruments require removal of the coating at the measurement point.
Further reading: Dakota CX2 vs CX4 vs CX8-DL · Corrosion gauge vs flaw detector · Echo-Echo and ThruPaint™.
Probes and measurement
In order: coupling, i.e. whether there is enough couplant and the surface is clean; the condition of the probe, in particular wear of the contact face; adjustment, which must be redone if material or probe has changed; gain, if the instrument allows it. On corroded surfaces the problem is often the irregular back wall, not the instrument.
In general, high frequencies give more resolution on thin thicknesses but penetrate less; low frequencies penetrate more and work better on attenuating materials, with lower resolution. The choice depends on expected thickness, material, temperature and geometry of the part.
There is no fixed interval: it depends on use. The contact face wears, and a worn probe gives unstable readings or no longer locks onto the echo. If measurements progressively worsen and coupling is correct, the probe is the first suspect.
High-temperature probes and a suitable couplant are needed; moreover the speed of sound in the metal changes with temperature, so the reading must be compensated. Some models, such as the CMX series, have a mode with automatic temperature compensation.
Further reading: How to choose the right ultrasonic transducer · How to improve results on difficult materials · Probes and Accessories.
Calibration, standards and services
The manufacturer’s generic recommendation is annual, but the correct interval depends on the company quality system, the sector and the intensity of use. EN 15317 and the client’s requirements are the references to follow.
No. Adjustment on a reference block adapts the instrument to the material and the probe and must be done at every campaign; periodic calibration certifies the instrument and its metrological traceability, and it is what an auditor will ask you for.
Yes. Calibration, repair and technical advice are also available for Dakota instruments purchased through other official channels. We do not, however, guarantee service on instruments of unofficial or parallel origin.
Product standards such as EN 14127 and ASTM E797 define the measurement method; EN 15317 concerns periodic instrument verification; sector standards such as API 570, API 653 and ASME PCC-1 require the instrument to be in current calibration and the readings to be traceable. In practice: calibrated instrument, documented adjustment, archived data.
Further reading: Calibration and adjustment · NDT standards for thickness measurement · Repair and service.
Did not find your question
Write to us describing the situation: instrument in use, material, expected thickness and what does not add up. In most cases the problem is solved at the first contact, without on-site work or shipping. Recurring questions then end up on this page.
For the rest of the support: Support and Resources.
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).