BS EN ISO 16526-2:2020 pdf free.Non-destructive testing – Measurement and evaluation of the X-ray tube voltage.
The equipment to be used includes the following components, see figure 1:the X-ray system;a specified collimator;a specified filter;suitable dose meter or dose rate meter;a film for the prove of good collimation and dose meter or dose rate meter adjustment.used for documentation. Figure 3 shows a typical radiograph of a dose meter which is well adjusted corresponding to figure 1. NOTE : The results of the measurement arrangement are reliable if it provides the same value in horizontal and vertical adjustment. Using the thick filter method, the measured values will change approximately 5 to 10 times faster (leverage factor) than the X-ray voltage changes. That means for example that 5 % of the X-ray tube voltage change corresponds to 25 % to 50 % of the measured dose rate.In order to carry out the constancy check of an X-ray system or the consistency check of an X-ray system to compare different components the dose rate is measured using a filter as given in figure 2 or thicker. 3.1 Leverage factor For the first application of the thick filter method the leverage factor Lv shall be determined corresponding to the selected setup. The dose value shall be measured at 100 % (D100) and at 95 % (Dg5) of the test voltage. NOTE The leverage factor should be adjusted between 6 and 8. This is a compromise which considers limitations in exposure time. A high leverage factor is recommended for high accuracy of the method. The leverage factor is calculated by equation (1) Lv=(1- D95/ D10o)/ 0,05 The constancy test of the tube shall be repeated regularly at the given voltage. The arrangement corresponding to figure 1 shall be used with the same collimator, thick filter (thickness and material) and the same calibrated dose meter for the constancy check. The constancy of the tube voltage is confirmed if the measured dose value or dose rate value has been reproduced within the required tolerance T (in %) which is calcualted by equation (2). T= 100. |(D100measured – D100nominal) | / (D100nominal. Lv)Within the reference measurement all essential parameters (distances D1 and D2, filter material and thickness, type of dose meter or dose rate meter) shall be documented. The arrangement shall be identical for all subsequent measurements. An example is given in Annex A.BS EN ISO 16526-2 pdf download.