Equipment, measurement accuracy and personnel qualification
Domain 4 - Equipment, measurement accuracy and personnel qualification
This domain tests imager selection, calibration, uncertainty, environmental corrections, and the qualification framework behind a trustworthy measurement.
Core rules
- Select by spectral band, detector resolution, NETD, accuracy, temperature range, focus, frame rate, radiometric storage, and lens/IFOV. Longwave 8–14 µm suits ambient work; shortwave suits high-temperature targets.
- Accuracy statements such as ±2 °C or ±2% apply only with valid ε, reflected temperature, distance, and atmosphere. Calibration must be traceable; verify with a blackbody and follow the manufacturer's interval.
- Budget uncertainty from calibration, emissivity, reflected temperature, atmospheric transmission, spot size, and repeatability.
- ISO 18436-7 defines Category I, II, and III thermographer requirements for training, experience, and examination. Category III manages programs, procedures, and advanced analysis; recertification and records are required.
- Keep training, certification, vision, and experience records; a certificate does not replace demonstrated competence.
Worked example
An imager has IFOV 2.5 mrad. At 8 m, one pixel covers 20 mm; a 3 × 3 measurement spot is 60 mm. A 15 mm terminal is therefore undersampled. Move to 2.5 m (about 6.25 mm/pixel; 18.75 mm spot) or use a telephoto lens. At 150 °C, a ±2% accuracy is ±3 °C, before adding emissivity uncertainty.
Traps
Trusting display accuracy without ε; measuring from too far; calibrating on a low-ε target; using an expired calibration; treating a certificate as qualification; and omitting records or uncertainty from the report.