Reply To: HYDROS 21 no longer vented… any idea when this changed?

Do note that the specifications says accuracy  0.5% of 10,000m or +/-50mm (edit  corrected to 50mm). This  implies that you want to keep it at a constant (20C?) while sitting in the bucket, and even then the apparent water level can wander up  +50mm  or down -50mm and still be within specification.    If the temperature changes then the accuracy specification doesn’t apply.

https://www.metergroup.com/environment/products/hydros-21-water-level-monitoring/

Water depth
Range: 0−10,000 mm
Resolution: 1 mm
Accuracy: ±0.5% of full scale at 20 °C

NOTE: Depth measurement accuracy assumes no abrupt temperature variations.

For environmentally significant flows (low water depth measurement, with high temperature variation) it has a lot of noise on the signal.

Great instrument for measuring borehole water pumping ground water that is usually a constant temperature and large variation in depth.