Chart recorders are devices that will record the trend of an input over time.  Most of them do this by drawing a trend line directly onto graph paper.  Although many of these devices are being replaced by digital methods of trend recording such as Historians and SCADA software you can still see them installed in many industrial facilities.

There are two basic types of paper chart recorders:

Circular Chart Recorders  

 Chart Recorder Picture

Continuous Line or Strip Chart Recorders

Strip Chart Recorder Picture