In order to maintain a constant statistical noise level, we must increase the penetrating capability of the x-rays with an increase in the nominal thickness setting.  If we did not increase the x-ray kV with a continuing increase in thickness, there would be a continuing decrease in radiation at the detector (hence a continuing increase in statistical noise).

     The PLC running under the generator reference menu creates and stores a curve from which the correct generator reference voltage setting for any given gauge nominal may be picked.  This so-called "calibration" cycle is totally automatic and may be run at any "off-line" time desired by simply calling up the generator reference calibration screen from the main menu and initiating the procedure via the touch screen.  This calibration is usually performed after the x-ray tube in the generator has been changed.

     In normal operation, the preset radiation level is trimmed by the detector to produce a zero deviation signal that is accurate to within ±0.1% of the nominal;  however, due to the accuracy of the generator calibration, the auto standardize sequence can, at the customer's discretion, be bypassed to produce an approximate zero deviation which is accurate to approximately 1/2% of the nominal.  This pre-calibration function can be useful in multi-pass operations where "absolute" information requiring the gauge standardization is used for the last pass only.

Back