Many recorders use a sheet of printed chart paper which is wrapped around a rotating drum. Typically these are barographs but variations include thermographs (temperature), hygrographs (relative humidity) and instruments combining two or all three of these.
With many of these recorders rotating very slowly, a week is common, the paper must be of the highest quality to avoid ink from the pen soaking into the chart, creating an unsightly “blob” and obscuring the data. By using pens and charts from Graphic Controls such problems are eliminated. |