Fastbus TDC Gain and Offset Calibrations

The Fastbus TDC gains and offset are calibrated using a time calibrator. The time calibrator sends a START signal to the TDCs and a STOP signal to the TEST inputs of the discriminators. The time difference between START and STOP is a multiple of 10 ns, with a maximum of 640 ns. The Fastbus TDCs have a dual range: in the lower range, the resolution is about 25 ps/channel while the resolution of the upper range is about 200 ps/channel. For more details, please refer to the TDC manual.

The procedure used to calibrate the TDCs is as follows:



This command produces the following output:

The calibration parameters calculated are displayed in a second canvas. An example obtained for run 6060 is shown below. The gain parameters (in ns/channel) are shown on the left for the low-range (top) and the high-range (bottom). The offset parameters (in ns) are shown on the right for the low-range (top) and the high-range (bottom). Three things should be checked:




Frank Wolfs, University of Rochester, June 2001