Heico EMD Epsilon EPS 45-80, Техническое руководство

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EPS 45-80 High-Voltage Generator
8-6
Technical Manual P/N 9894.00.G6
8.2.3.6 Validation of AEC Mode
Perform this procedure to validate that the AEC mode is functional.
l- Quick method
1. Set-up the following 3-point AEC exposure: near 100 kV, 500 mA and 1.0 BUT.
2. By reducing the collimator aperture or by introducing aluminum phantom into the X-ray beam,
put enough filtration so that the exposure last for about 0.5 s.
3. Reduce the kV to about 60 kV.
4. Make an exposure and verify that the exposure is stopped by backup mAs detection (600 mAs).
5. Fully open the collimator (or take off the aluminum phantom).
6. Repeat the same AEC exposure and verify the exposure is stopped by phototiming feedback
(irradiation mA x time product less than 600 mAs).
ll- Detailed method for Ion Chamber AEC Device
1. Make certain that for the workstation being used that an ion chamber is selected as the AEC
device and that the ion chamber is in fact connected to the same connector as configured in the
workstation menu of Epsilon PC Tools.
2. Select a three point AEC exposure (kV - mA - BUT - BUmAs) with reasonable kV and mA and
a BUTime of 500ms. Select Medium Film Screen and all three fields ON.
3. Make a note of the Ion Chamber nominal voltage visible in the AEC menu of PC Tools for the
selected Ion Chamber for the Medium Film Screen. For these tests, place the correction table
values to all zeros for the medium film screen.
4. Connect an oscilloscope with one channel on Main Gate (TP17, Controller Board) and one
channel on pin 1 of the eight-pin connector where the Ion Chamber is connected. Trigger the
scope on the rise of Main Gate.
5. Attempt to perform an exposure.
Possible outcomes are:
i) The console displays “AEC/ABS DEVICE OPEN”
a) Check the voltage on Pin 1 of the Ion Chamber connector. If it is above a few tens of
millivolts, that implies that either the chamber is not connected properly or that the chamber
hardware is not configured properly. Verify the connections. If connections are OK, the problem
is with the hardware configuration. Go to the AEC Configuration Screen of Epsilon PC Tools
and for the Ion Chamber in use modify the hardware selections. For most common AID
chambers, the proper settings are:
Output High Voltage : 12 Volts
Reset Polarity : Reset
Field Polarity : Low Selected
b) BUT : Using the Ion Chamber users manual, verify that the configuration is correct for the
chamber being used. If the Ion Chamber signal (Pin 1 of the connector) is above a few tens of
millivolts before the exposure starts and it is properly connected then either the Output High
Voltage is set wrong for the chamber or, more likely, the reset polarity is incorrect.