Add Watermark 200ss support

Pseudo-AC Short Pulse required, see https://www.irrometer.com/200ss.html

````
OUT_1 ---+
         |
ADC_1----+---+
             |
            R_2
             |
ADC_2--------+
             |
          R_Watermark
             |
ADC_3----+---+
         |
OUT_2----+
````