Generator Firmware (Pro, RT, VCT)

The generator firmware runs on the kV control board's Power PC CPU. Its main functions are:

• console and/or system communication

• exposure sequencing (rotation, heater, exposure control, mA regulation)

• tube/generator thermal protection

• image quality algorithms

• tube calibrations

• tube/generator tracking

• generator diagnostics (application background diagnostics and service diagnostics)

The generator communicates via a Controlled Area Network (CAN). Each communication path is connected to the application software through a communication driver. This mechanism allows:

• The same generator behavior regardless the communication path used to drive the generator (other types of X-Ray systems use CAN in conjunction with other types of communication)

• Connecting several interfaces at the same time on the generator

See kV, mA, and rotation functions.

The generator firmware counts the number of tube spits occurring during an exposure.

The count generates an error if:

• the number of tube spits exceeds the maximum number allowed for CT applications this is (100+8*T) spits where T is the exposure time in seconds

• tube spit rate exceeds the maximum allowed. For CT applications this is 20 spits/0.1s.

In both cases, the exposure is stopped and the error is reported to the system.

If the count does not exceed the limits, the number of spits is reported to the system at the end of the exposure. A cumulative count of tube spits is stored in the TnT database, or can be viewed using the Real-Time Stats viewer.

Tube filaments age during tube life leading to mA inaccuracy over time. To maintain mA accuracy, the mA accuracy is tracked over a tube's life. At the beginning of each exposure, the difference between the mA demand and the real mA is measured and the drift is recorded. This drift is used with a slow time constant to correct the filament drive's initial values. During the generator's life, the generator firmware logs the drift on both focal spots in the TnT data.

The filament aging coefficients are found in the TnT database. For serviceability there is nothing to be done with filament aging coefficients.

The filament aging coefficients can be thought of as the fine-tuning of tube calibration. The filaments must be properly calibrated before the aging parameters are used. Without proper filament calibration, the aging parameters will not matter.

Part of the generator firmware includes a database. This database consists of two parts: Configuration Data and Run-Time Parameters. Configuration Data is used by generator firmware to properly control x-ray. The only exception is that the filament aging coefficients are stored in Run-Time Parameters, and are also used to control x-ray.

All Run-Time Parameters update at each scan and the data is stored for troubleshooting.

Figure 1. JEDI Database

Excluding Inverter and kV board replacements, Configuration data is changed when:

• Flash Download Tool downloads firmware to the JEDI

• The default database is downloaded to the JEDI

• Filament Calibration is successful

Run-time parameters are changed when:

• Tube TnT data is reset

• Generator TnT data is reset

• Filament Calibration is successful

• Run-time parameters are restored

• An exposure has been completed and new data is logged

The generator tracks both tube and generator usage statistics. The statistics are stored in the Run-Time Parameters section of the database. This data is generally viewed using the Real-Time Stats viewer, however it can also be viewed using JEDI Generator tools.