Elk M1 + water sensing using voltage change

[dtreyes]

I've seen several posts recommending water bug, water leaf sensor, 2600 and other water sensing device to connect to elk input to sense water. I tried connecting a 470k resistor between the input and neg wires and noticed that voltage dropped to 9.7 when the two wires were soaked in water and 13.6 when not. Now, if I configure the zone as analog and create a rule so that if voltage drop to say 12, water is present, will I get realiable results. Also can I use input on input expander instead to input 1-16 ??? Thanks.

 

[elcano]

It will work for some time. However, since the analog sensor uses DC current, you will have a permanent anode/cathode pair. Ions will flow in one direction only and the terminals (well , at least one of them) will get dirty or oxidized (not sure now). This will reduce the conductivity and decalibrate your sensor.

All current based water sensors use AC current to neutralize this problem. Terminals will switch polarity constantly and the ions will not be able to stick to the terminal. Some of them are even gold coated to minimize the corrosion effect.

 

[Spanky]

Normally, the probes are not in water so there is no plating to the probes on the sensor. We demonstrate sticking a stripped wire into a glass of water in our training class. No other resistors are needed, just program a normally open zone input.