Normally, the XY chart will retain previous zoom level on a chart's main axis (usually X-axis) across data updates. However, the Y scale will be updated to fit the new values.
This demo shows how we can add an event to the series to retain the same zoom level across data updates.
See the Pen
Retaining zoom after data update on an XYChart by amCharts team (@amcharts)
on CodePen.0