Air Pressure
A barograph fitted with a weekly chart. The previous week's chart is displayed in a plastic cover above the barograph.
At the end of each week when I change the chart, I use the barograph stylus to mark the actual time I made the chart change. It is difficult to get the trace matched up with the correct time. The sample above hit the correct time. However for weeks that the trace is off, the time maker allows the observer to make the time correction when reading other portions of the chart.
Larry
My email address: