exposure charts

exposure charts

1. M.KARTHIKEYAN ASSISTANT PROFESSOR DEPARTMENT OF MECHANICAL ENGINEERING AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI [email protected] ME8097 NON DESTRUCTIVE TESTING AND EVALUATION

2. UNIT V RADIOGRAPHY (RT) Principle, interaction of X-Ray with matter, imaging, film and film less techniques, types and use of filters and screens, geometric factors, Inverse square, law, characteristics of films - graininess, density, speed, contrast, characteristic curves, Penetrameters , Exposure charts, Radiographic equivalence. Fluoroscopy- Xero -Radiography, Computed Radiography, Computed Tomography

3. RADIOGRAPHY: EXPOSURE CHARTS Introduction X-ray exposure charts are individual to the x-ray machine, intensifying screen, film and developing combination. An exposure chart for one x-ray machine cannot be transferred to another machine even if it is identical. Exposure charts are important to: Provide consistent results. Reduce number of exposures (important for radiation safety and cost). Allows direct comparison between films taken on different dates in the same animal .

4. When compiling an exposure chart as many variable as possible should be kept constant: Film focal distance. Object film distance. Processing. Film type. Intensifying screen type. Use of grid. Line mains compensation. Several charts may be needed for different film/screen combinations and different species.

5. Radiographic Equivalence Factors It is that factor by which the thickness of the material should be multiplied in order to determine what thickness of a standard material shall have the same attenuation. This may be used : a ) To determine the practical thickness limits for radiation sources for metals other than the standard materials, and b ) To determine exposure factors for one metal from exposure charts compiled for other metals.