The document `Single Detector Signal Jumps', by A. Heras, 9 June 1997, summarizes a study made on single detector signal jumps. These effects occur in only one detector at a time and can be generally described as a sudden increase or decrease of the signal, which then remains constant or has a long recovering time (>> 10 s) after the jump. These jumps are normally seen at low signal levels. Examples of such jumps in SPD data are shown in figure 5.12
The signal jumps observed for each detector vary significantly between different cases, and may be negative or positive.
Jumps in band 3 are of different nature from jumps in bands 1 and 2.
The frequency of jumps in bands 1 and 2 is of approximately 5 jumps per hour.
The signal jump is more clearly reflected on the first second of the reset interval than in the second one, indicating a relation between the signal jump and a residual after reset pulse effect. This will be further investigated when working on a possible correction for these jumps.
For bands 1 and 2 and for the measurements with a reset interval of 2 seconds, half of the jumps are associated with the detection of glitches. However, no correlation has been found between the characteristics of these jumps and and those of the glitches.
Users are recommended to examine the SPD from their observations to look for such jumps. If they are present the user can either throw the affected portions of the data away or try to adjust the baseline of the affected portion to the pre- and post-jump baseline.
