non-destructive method
direct visual testing
indirect visual testing
videoscopy
mobile or in-house

Visual Testing (VT) is one of the oldest and most important non-destructive testing methods. It enables quick and reliable detection of surface defects such as cracks, pores, cavities or weld irregularities – without damaging the component.

Direct visual testing: performed with the naked eye or optical aids directly on the component.

Indirect visual testing: used when inspection areas are difficult to access – e.g. with mirrors or endoscopes.

Videoscopy: modern camera-based inspection with high-resolution documentation. Ideal for complex geometries or hardly accessible cavities.

Our experts work with state-of-the-art equipment to reliably detect even the smallest irregularities. All results are documented in detail and provided to you as a test report.

“Seeing what others miss – with certified visual testing.”

Zeros GmbH is an independent testing laboratory for destructive and non-destructive materials testing. We support companies from incoming inspection to series release – including digital test reports and full traceability.

We operate under accreditation to DIN EN ISO/IEC 17025 (quality management for laboratories). See our current accreditation information here.

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We are accredited by DAkkS to DIN EN ISO/IEC 17025. This standard ensures that test methods, equipment control, personnel qualification and reporting meet the highest requirements.

An overview of services and scopes is available on our homepage.

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Our portfolio covers NDT (UT, RT, MT, PT, VT), mechanical testing (tensile, hardness, Charpy), metallography (microstructure, grain size, coating thickness) and chemical analysis (e.g. OES, XRF). We also provide specimen preparation, documentation and consulting.

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Overview of visual testing methods

Visual testing is used in almost all industrial sectors. It is the basis of many testing concepts and enables rapid detection of surface defects.

Direct visual testing – Procedure

In direct visual testing, the image reaches the eye without detours. Observation, detailed evaluation and assessment of detected defects are usually performed by one person in a single step. Testing according to DIN EN 13018 requires a valid test instruction. Direct VT testing can be supported by aids such as mirrors, endoscopes or magnifiers.

Indirect visual testing – Procedure

When inspection areas are difficult to access, visual testing is performed indirectly. Aids such as mirrors, endoscopes or videoscopes are used. For indirect methods, DIN EN 13018 also requires the provision of a test instruction.

Example: procedure of direct visual testing

1. Component preparation

Clean and expose surface.
2. Lighting

Use suitable light sources.
3. Visual inspection

Direct observation or with optical aids.
4. Documentation

Record results photographically or in writing.

Typical applications

Welds in steel structures
Mechanical and plant engineering
Pipelines and vessels
Surface inspection in series production

Visual Testing VT |
direct & indirect

How visual testing (VT) works

Non-Destructive Methods

Ultrasonic Testing (UT)

Radiographic Testing

Magnetic Particle Testing

Penetrant Testing (PT)

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Basics, Methods & Procedure of Visual Testing

Visual Testing VT | direct & indirect