How to Create a Custom Control (Widget) in Qt ?

I am in need of creating a custom Control for one of project. It is industrial based application where I need to create control of different gauges like Voltmeter, Meter like Speedometer kind for e.g . I need to understand how can I create such an control and also advice me for better approch towards creating such a control. Any samples would be helpful

Have a look at the Analog Clock example.