BS EN ISO 16526‑2:2020 pdf download.Non-destructive testing – Measurement and
evaluation of the X-ray tube voltage.
1 Scope This part of ISO 16526 specifies a constancy check of a X‑ray system where mainly the X‑ray voltage is checked and also the tube current and the constitution of the target which can be changing due to ageing of the tube. The thick filter method is based on a measurement of the dose rate behind a defined thick filter using defined distances between the X‑ray tube, the filter and the measuring device. This method is very sensitive to changes of the voltage, but it does not provide an absolute value for the X‑ray tube voltage. Therefore, a reference value is needed and, it is recommended to find this reference, for example, within the acceptance test of the system. The thick filter method is a rather simple technique and may be applied by the operator of an X‑ray system to perform regularly a constancy check of the system. The method can also be applied for consistency checks after changing components which may affect the X‑ray tube voltage. This method can be applied for all types of X‑ray systems, i. e. for constant potential, half wave and impulse wave generators with a tube current larger than 1 mA.
2 Principle and equipment
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.
4 Test report
The test report of the measurements shall contain at least the following information:
a) reference to this part of ISO 16526, i.e. ISO 16526‑2:2011
b) X‑ray system, type and fabrication number;
c) the X‑ray parameters: voltage (kV), current (mA) and the selected focus size, preferably the
nomimal voltage and the maximum current;
d) type and size of collimator;
e) filter type and thickness, preferably with identification number;
f) dose rate meter, or dose meter, also with identification number;
g) focus to filter distance;
h) focus to dose rate meter distance;
i) drawing of the setup if it deviates from figure 1;
j) the measured value and the measured leverage factor;
k) the date of the measurement;
l) the deviation from the reference value;
m) name and signature of operator.BS EN ISO 16526‑2 pdf download.