Journal
Marking drift on a figure instead of arguing with the probe
Drift is a slow walk of the line, not a jump. Jumps usually have stories: a door, a start-up, a probe pulled for cleaning. Drift has fewer witnesses. A humidity sensor in a glasshouse that reads a little higher every week may be a wetter month, a clogged filter, or a sensor that wants replacing.
On our pages the walk stays on the figure. We do not subtract a guessed slope to “correct” it unless you supply a calibration day with a known reference. Even then we prefer a note in the margin — “calibrated against the handheld at 14:10” — over a silent shift of every earlier point.
The written reading can say the line climbed. It should not say “the probe is faulty” unless someone on site has already compared it to a second instrument or a salt check, and told us so. Guessing the hardware from the armchair in Kutaisi has wasted meetings before.
If you suspect drift, send the date of the last check and whatever handheld or glass you used. We will mark that hour. The rest of the series remains as stored. Readers can then argue about cause with the evidence still on the paper.