This procedure outlines the calibration procedure for densitometer. 2
Reference Standards
ASME Section V - Article 2, T-262 3
Definitions
3.1
Primary Reference Standard
Is the calibrated Transmission Density Step Wedge which is calibrated in comparison with a National Institute of Standards & Technology (NIST) Film Step Tablet - Standard Reference Material 1001. 3.2
Reference Transmission Density Step Wedge Film (SWF)
Is a strip having at least 5 steps with neutral densities from at least 0.3 through 3.9, calibrated by comparison with the Primary Reference Standards. 3.3
Densitometer
Is the instrument (either direct scale readout or digital readout displays) used to read transmission density of films. 4
Initial Calibration Of Densitometer
Adjust 'O' reading reading of the densitometer by the following method: With nothing on the film viewer, place the proble over the reading reading target, then press read button. button. Adjust the ZERO control until the value on the display reads 0.00. Select and position for reading the neutral density closest to 1, 2, 3, & 4 on the Primary Reference Standard for densitometer adjustment. Read and record these densities. Compare them to the actual densities listed on the Primary Reference Standard. If any of these densities vary more than + or - 0.05 density units from the Primary Reference Standard, then the linearity of the instrument is out of tolerance and shall be corrected. 5
Calibration And Periodic Verification Of Densitometer
The densitometer shall be calibrated every 90 days using a primary reference standard. If the reading differ by ±0.05 density units from the readings marked on the primary reference standard, then the linearity shall be corrected and the densitometer recalibrated. Periodic verification of the densitometer shall be done using reference transmission density step film wedge or primary reference standard at the beginning of each shift, after 8 hours of continuous
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operation, after after change of apertures whichever whichever occurs occurs first. Calibration verification verification readings readings need not be recorded. recorded. It is necessary necessary to ZERO ZERO and calibrate calibrate the instrument instrument before daily use. use.
