Note that there is a cap on the number of results you can display on a chart. If you are going to use a 1s (one second) span, then you are going to have to limit the time range you are looking at significantly. Specially if you have multiple sourcetypes that you are charting.
Hi a212830
updated
I think you are looking for this
yourSearch | bucket _time span=1s | chart count over _time by sourcetype
not for this
yourSearch | timechart span=1s count by sourcetype
cheers, MuS