Aurora, Illinois - When a radiographic tube is installed properly, the default filament curve is typically used as a starting point for calibration. This action is accomplished while following the calibration or service manual for the generator installed on your system. Some radiographic systems will monitor the tube mA output and adapt the filament current to ensure the correct tube mA output is achieved. Other radiographic systems achieve the correct mA output through manual verification/adjustments during planned maintenance sessions. Typically, in both cases, the filament current is increased over time to maintain proper tube current output.
Example: A radiographic tube is installed on a system that does not automatically adapt to filament aging. The tube is installed on Jan 1, 2011. The default filament curve is used at installation. For a technique selection of 80kV, 100mA, .5sec, the filament current will be 4.7 Amperes. Three years later (after several PMs and mA adjustments), that same technique selection of 80kV, 100mA, .5sec, can require the filament current to be 5.6 Amps.
Let's say that tube fails during the third year. When the new tube is installed, the filament current is higher than the default filament curve if it isn't reset (greater than 5.6 Amps for an 80kV, 100mA exposure). This will typically lead to overdriving the filament (damaging the filament and the target), eventually leading to premature tube failure (usually open filament or reduced x-ray output).
Our Technical Support Team is available 24 x 7 at 800.238.3780 to answer any further questions you may have.
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