Someone was surprised to see a graphic display on my bench meter of long term drift on this post
https://www.eevblog.com/forum/product-reviews-photos-and-discussion/looking-for-goodinexpensive-bench-power-supply/msg114215/#msg114215 so I thought I would start this thread to show how trend plot works on the 8846A bench meter. Trend plot sampling rate follows whatever reading rate the meter is currently set for. Trend plot has two controls, start and stop. These screen shots are from a PD 2005A power supply in CC mode at approx. 200mA directly connected to the meter 400ma input. Meter is set at 6.5 digit mode at 100 NPLC (integrates over 100 power line cycles so in US 60Hz is about 1.7 seconds per reading)
Cold meter and power supply both turned on at the same time so we are going to plot the warm up of the meter and PS. Trend plot started and it has taken roughly 6 Min's to fill the horizontal time axis. The vertical axis continuously autoscales to accommodate the min and max reading span. In this case 11.99 mA.
When the plot reaches the right border of the display it is autoscaled horizontally to mid screen and continues. The plotting rate is now cut in half and it continues. This pic is when the plot is almost to the right border again after roughly 11.5 Min's and the plotting rate is now cut in half again and it continues and the vertical axis has autoscaled to accommodate the 13.45 mA span.
Again When the plot reaches the right border of the display it is autoscaled horizontally to mid screen and continues. The plotting rate is now cut in half again and it continues. This pic is when the plot is almost to the right border again after roughly 25 Min's and the vertical axis has autoscaled to accommodate the 14.93 mA vertical span.
This is right after the above plot reaches the right border and it autoscaled horizontally to mid screen and vertically to accommodate the additional 0.06 mA. The plotting rate is now cut in half again and it continues.
Roughly 25 Min's more and the vertical axis has continuously autoscaled to accommodate the 16.31 mA vertical span.
This is right after the above plot reaches the right border and it autoscaled horizontally to mid screen. The vertical did not need to change. The plotting rate is now cut in half again and it continues.
20 more minutes has elapsed and I can now graphically see that things have basically settled out, but now I don't have the resolution to see how stable it is. Next post will fix that problem.