How to plot a graph with real-time data

I want my time-series char widget to display real-time data in the Mashup as soon as the data field property's DataChangeEvent is triggered. I've tried with the following two approaches, but none of them work.

1. Using the 'Refresh' widget with interval set to 60 seconds, and

2. Using the GetProperties service, with 'Automatically update values' flag checked, and the 'ServiceInvokeComplete' event bind to 'QueryPropertyHistory' service (which has its return data bound to the chart widget).

I've two remotely bound properties in my Remote Thing, one String type and the other Number type, both logged, and an associated Value Stream. The Number type property has 'DataChangeEvent' set as 'Always' and the String type property as 'Value'. The Number type property gets updated every 60 seconds. Upon executing the 'QueryPropertyHistory' service manually in the Composer UI, I find that the returned table does not contain rows spaced 60 seconds apart. Many of the rows are only milliseconds apart, while some rows are few minutes apart. I also checked the 'Application Log' to see the DataChangeEvent firing logs, and they aren't triggered every 60 seconds either.