Fluke Biomedical TNT 12000 - Manual (Page 121)

E-1
Appendix E
TNT 12000WD kVp, Exposure, and
Exposure Time Measurement
Introduction
The TNT 12000WD measures kV, exposure, exposure time, and HVL for all
radiographic x-ray imaging modalities. This includes Radiographic, Mammographic,
Fluoroscopic, and Dental, and can measure kV for stationary mode CT. All kV
measurements are automatically corrected for beam filtration. All exposure
measurements are automatically corrected for kV and beam filtration.
When the measurement mode parameters are set to Auto, the X-ray Detector examines
the waveform type. The results of the analysis, along with the X-ray machine type lets the
Detector set the applicable analysis procedure for the measurement. Read the sections
that follow to learn how the analysis finds the measurement procedure.
Radio Waveform Analysis
In the Radiographic mode, exposure, exposure time, and kV measurements are done as
follows:
Single Phase
Exposure time in milliseconds is calculated between the first and last zero crossings of
the kV waveform. Exposure time in pulses is measured between the first and last zero
crossings of the kV waveform.
The Detector measures average kVp on the pulses in the central 80 % of the kV
waveform. It measures Maximum kV and PPV on the complete waveform. Exposure is
measured from the start of the exposure to the end of the exposure.
Three Phase
Exposure time in milliseconds is calculated between the 75 % points on the rising and
falling edges of the kV waveform.
The Detector measures average kVp on the pulses in the central 80 % of the kV
waveform. It measures Maximum kV and PPV on the complete waveform. Exposure is
measured from the start of the exposure to the end of the exposure.