Watermark sensors can experience problems where the readings suddenly jump up to 200 cbar (kPa) and flatline, as shown in this screen capture:
screenshot: 2 already very dry watermark sensors flatline at 200 cbar, Basil, Bakersfield, CA
This can be caused by three reasons:
- Watermark sensors losing good contact with the soil
- Water has corroded the wires in the scotchlok
- There is no/not enough contact between the wildeye wires and the watermark
Watermark sensors losing good contact with the soil
Watermarks can lose contact from the soil more easily than water content sensors which use electric fields instead of contact to detect water (water content sensors can still experience air gaps, but that is usually due to poor installation or rocks during installation, once they are settled air gaps are rare).
Soil contact loss is particularly noticeable in tree crops during large gaps in irrigation, or as in this example some short-term crops like basil when the ground is left to dry prior to harvest.
Once the watermark sensor loses contact, in most cases it will need to be re-installed.
If there is any doubt about the sensor working correctly, confirm that the sensor is working prior to re-installation by dipping it into water, as shown in this screenshot:
screenshot: 2 watermark sensors removed and dipped in water, Basil, Bakersfield, CA
Water has corroded the wires in the scotchlok
If the scotchloks experience flooding in which the scotchloks are submerged under water for a duration of time, the wires can corrod which prevents electrical contact. Easiest way to remedy this is by cutting back the wire and attaching a new scotchlok.
There is no/not enough contact between the wildeye and the watermark
Check the connection at the end of the wildeye or expander to check that there is a watermark. If the wildeye is not attached to a watermark sensor the wildeye will report this as 200 kPa.