Hi all, I'm building a machine that needs a piece of fabric about a 4 feet wide and a foot in height to stay wet but not drip excess water onto the ground. I was hoping to run a wire in a wave type pattern in the fabric and measure the resistance change as water collects between the waves. I haven't seen any examples of this so I'm worried it won't be possible.
Thanks in advance for any advice
Possible work if your wire is VERY high resistance and the water is made conductive with salt or similar.
Hi, @stcoky
Welcome to the forum.
What is t he application?
Evaporative Air Con/cooler.
If you are blowing water across or through it, measure the resulting air's humidity.
If you tilt your sheet of fabric, then any excess should run off the lower edge.
Just some thougths.
Tom.. 
Hi, thanks for your input, this will be for a chemical applicator for weeds. I need the fabric to be adequately wet to transfer chemicals upon contact but not so wet that it drips chemical into the soil. I have considered measuring the weight of the fabric but with plants constantly dragging on the fabric it would not be very accurate. Got any ideas?
You may aldo measure temperature...
The temperature of a wet cloth will be lower than the ambient temperature.
If they are equal, the cloth is dry.
Can you show a sketch of your idea?
I'm thinking you can measure the weight of the fabric. More wet = more weight
Don't have a sketch yet as I am unsure of what type of applicator to use. Weight might be a good option but since it will have plants brushing against it there could be a lot of interference in that measurement
Won’t you loose a lot of the water from evaporation , leaving an increasingly concentrated mix on the cloth?
Can you not control the amount of liquid going onto the cloth , maybe temperature compensated just to keep it damp , or detect the drips off the bottom ?
Wet the fabric to your desired wetness.
Weigh the wet fabric at that desired wetness.
Stop wetting the fabric at the desired weight.
Moisture will probably affect the fabric's dielectric properties, so a capacitive method might work: pass the fabric between two plates and measure the plate capacitance.
Now that sounds like a good idea, I've seen this method mentioned a few times. I'll look into it and see if its something that would work with my setup. Do you know much about it? Would it be a difficult thing to setup with an Arduino or is there aftermarket boards for this? Cheers dude
I'd be thinking along the lines of applying variable amount of wet agent relative to speed of application.
There is an arduino capacitive touch library that may be helpful. Without doing the math, I don't know what levels of capacitance to expect, so I don't know if the library will help.
That said, it's pretty simple to measure capacitance: you basically put the unknown capacitor and a resistor in an RC circuit and apply a voltage to one end of the resistor and measure how long the voltage takes to rise at the other end. If you want to try it, I'm game for helping.
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