3D
AEC Calibration
CPI Canada Inc.
Use and disclosure is subject to the restrictions on the title page of this CPI document.
Page 3D-36
Rev. A CMP 200
®
Service Manual Ch # 901476-05
3D.8.2 AEC Calibration Range
Since the CMP 200
®
family of X-ray generators allows for up to three separate film screen combinations to
be calibrated, the following points must be considered:
•
The AEC board allows for a zero to a maximum of 10-volt ramp at the comparator input. All AEC signals
must fit within this range (for all film / screens, densities, and techniques).
•
Most X-ray film-based applications require the use of two or more different film screen combinations, all
of which will require different exposure doses.
•
Using the slowest film screen combination, the required film input dose will be determined.
•
Once this value is determined (during AEC calibration), the density calibration is performed to allow
100% (double the dose) and 50% (half the dose) values. These are typical values, and will determine
the maximum required range of the AEC reference voltage (the output from the D/A converter).
•
Figure 3D-10 illustrates the different windows required for various film screen combinations.
0
-8
-8
-8
+8
+8
+8
SLOW
FAST
X = Knee dose (density) at 75 kV
= Half the knee dose
= Double the knee dose
MEDIUM
AEC CALIBRATION NUMBERS (D/A OUTPUT)
x
x
x
10
20
FILE: ML_AECDA.CDR
30
40
50
60
70
80
90
100
Figure 3D-10: Film/screen speed vs. D/A output
