密度计校准程序DENSITOMETER CALIBRATION PROCEDURE.docVIP

DENSITOMETER CALIBRATION PROCEDURE NDE07-06 Revision 0 Date 30/04/2017 Page PAGE 1 of NUMPAGES 6 DENSITOMETER CALIBRATION PROCEDURE 3 2 1 0 REVISION PREPARED BY REVIEWED BY APPROVED BY AI 1. Scope This procedure covers the calibration of transmission densitometers used to perform radiographic film density measurements and provides a means of evaluating the reliability of transmission densitometers used for the measurement of radiographic film density. This procedure is prepared reference to T262 DENSITOMETER AND WEDGE COMPARISON FILM” of ASME Sect.Ⅴ. 2. Apparatus 2.1 Apparatus should consist of the following: 2.1.1 The X-ray film step tablet standard of the National Center of Measuring having at least 5 steps with neutral densities from at least 1.0 through 4.0. The calibration of the step wedge film shall have been verified within the last 12 month by comparison with a National Center of Measuring serialized step tablet. 2.1.2 Transmission Densitometers with digital readout displays specifically manufactured for the purpose of measuring the range of film densities, described in 2.1.1 shall be used. 2.1.3 Manufacturers Operating Instruction for Appropriate Transmission Densitometer. 3. Calibration 3.1 Full-scale linearity calibration of densitometer shall be performed at least every 90 days during use. 3.1.1 Allow a minimum of 30min warm-up time. After this warm-up period, adjust the 0 reading of the densitometer. 3.1.2 Select and position for reading the neutral density closest to 1.0，2.0，3.0，4.0 on the calibrated step tablet. Read and record the density for each step. 3.1.3 Compare the densities recorded with the actual density values listed on the calibrated or the density value listed on the calibration certificate. If the densitometer has been calibrated properly, the densities at 1.0，2.0，3.0，4.0 should not vary more than ±0.05 density units. If any of the recorded density vary more than ±0. 05 density units from the density values on t