Why We Recalibrate Every 45 Days, Not Every Quarter

Every water-quality sensor drifts — it's a question of how much, and how fast. For the first two years of the network we ran a quarterly calibration schedule, which is fairly standard in the field. Then we pulled the pre-calibration drift numbers across every station for those two years and didn't love what we saw.

The pH probes were the worst offenders: several stations were reading between 0.15 and 0.3 pH units off by the end of a quarter, which is enough to flip a borderline reading across a regulatory threshold. Dissolved oxygen and turbidity drifted less, but not negligibly.

We moved the whole fleet to a 45-day cycle in early 2025. It costs more in technician time. We think it's worth it.