Watermark sensors measure water tension. These sensors measuring range is between 100 and 2000
mBar (10 to 250 kPa or cB). This sensor fits many horticultural crops, berries, stone fruits, vines and
potatoes. Watermark sensors are easy to use and frost-proof.
Basically it is a gypsum block. The gypsum is embedded in a matrix material and gives a defined response
in resistance on different water tension levels. We can measure the water tension on 3 to 5 cBar accuracy.
It showed that it works faster if it is wetted for 24 hours before installation. If you install it in the ground
you will need a hole with the correct depth. Lay it horizontally on the ground and let the cable go
horizontally first to before you take it up to the top. This avoids water following the cable in the ground,
thus reaching and wetting the sensor.
The watermark PCB can be equipped with an own soil temperature sensor. This sensor is used to do the
temperature compensation of the water tension measurement. It allows you to to measure the soil
temperature in specific blocks where you measure water tension. The irrigation might influence the soil
temperature what can be important in asparagus for example.