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General
- During an X-ray exposure a dose equivalent ionization current is   generated in the AEC Sensor and a corresponding cut-off signal is   created and transferred to the X-ray generator.
  The AEC sensor ensures a reproducible optimal exposure   independently of beam quality, patient thickness and any other   factors. Using an AEC sensor avoids over or underexposure of the   image and helps to reduce patient dose.
Configuration
  • The ionization chambers for AEC are air-filled parallel-plate chambers with typically one, three or five independent sensor fields. Several different outer dimensions are available. Each VacuTec ionization chamber is equipped with a preamplifier and electronics, which converts the low ionization current into EMC stable digital signals (see figure below). Additionally it supplies the voltage for the chamber operation and allows selection of the sensor fields. Optionally the digital output signal can be transformed into an analogue voltage by using an additional ramp module.

    The positioning of the AEC sensor is close to the image detector. If an anti-scatter grid is used, the sensor has to be placed between the grid and the image detector. The AEC sensor has to be connected to an automatic exposure controller at the generator site.
Calibration
  • Each VacuTec AEC chamber is factory calibrated to radiation quality RQA5.
Part No No. of Measuring fields Connector size (mm)
142 00 17 1 Sub-D 9 pin 140 x 140
142 00 13 1 Sub-D 9 pin 374 x 374
142 00 14 1 RJ45 374 x 374
141 00 18 3 Sub-D 9 pin 374 x 374
141 00 19 3 RJ45 374 x 374
145 00 44 3 Sub-D 9 pin 450 x 450
145 00 45 3 RJ45 450 x 450
151 00 21 3 Sub-D 9 pin 450 x 450
151 00 22 3 RJ45 450 x 450
139 00 03 5 Sub-D 15 pin separate electronics 450 x 450
Part No Description
902 00 42 for 1 and 3 field AEC chambers
902 00 11 for 1 and 3 field AEC chambers, with cable extension
903 00 11 for 5 field AEC chamber, with cable extension
Energy range/tube voltage (40 ... 150) kV
Dose rate range (0.5 ... 1000) μGy
Exposure dose range ¹) (1 ... 100) μGy
Digital resolution (selectable) 0.025 μGy
Eposure time range ¹) 1 ms ... 10 s
Sensitivity difference between sensor fields ＜5%
Attenuation factor ¹) ＜4%
Aluminium equivalent ＜ 0.75 mm Al
Supply voltage (positive and negative) ± (11.5 ... 16) V DC
Digital output Differential signal (RS 422), pulse width 2 μs
Ramp output (with ramp module) 0 ... 10 V
¹) According to DIN 6815 dose measurement is carried out as follows: the air kerma (in Gy) is measured immediately downstream of the combined scattered-ray grid/measuring chamber using a radiation quality attained at a high-voltage of (70...80) kV and an Al attenuation layer thickness of 25 mm
For detailed technical information please require our documents.