A type of chart recorder where the pens write on to a circular chart that revolves once over a fixed time period (e.g. 1 day, 1 week etc). The pen sweeps across the chart in an arc to give a graphical view of the data over time.
The data compressed towards the centre of the chart due to the relative slower linear movement of the paper in the centre compared to the outer edge.
The 10 or 12 inch diameter circular charts are more easily filed or attached reports when compared to torn off pieces of strip charts.