> I am looking at options to chart dynamic data held in the PostgreSQL
> database pushed out to the web 'pages' via PHP, time series data in a
> scientific setting such as groundwater levels from a transducer…
>
You lost me on 'groundwater levels from a transducer', but we use
http://www.aditus.nu/jpgraph/
You'll need to check if they have the type you're looking to create.
I believe they have a version for <$100.