hot water read system

The setup: one short pin at top of boiler and two long pins running parallel to eachother acting as 'variable' resistor in voltage divider circuit and therefore can be used water level read. One of the long pins has the voltage signal and the other long pin and short pin are both running through relays so I can complete (or open) a circuit between the two as necessary.

My problem in the top short pin which is supposed to be used as a way tell if the boiler is full. When water drops under the pin, ideally the signal would go from 1 (high) to 0 (low). However, the pin does not go high to low. I checked with analogRead functionality. Instead, it gradually lowers, even when it's clearly under the pin (not touching water).

Could it be that the steam is causing the phenom? Anybody else had similar results and any ideas to fix issue?

UsernameD:
The setup: one short pin at top of boiler and two long pins running parallel to eachother acting as 'variable' resistor in voltage divider circuit and therefore can be used water level read. One of the long pins has the voltage signal and the other long pin and short pin are both running through relays so I can complete (or open) a circuit between the two as necessary.

My problem in the top short pin which is supposed to be used as a way tell if the boiler is full. When water drops under the pin, ideally the signal would go from 1 (high) to 0 (low). However, the pin does not go high to low. I checked with analogRead functionality. Instead, it gradually lowers, even when it's clearly under the pin (not touching water).

Could it be that the steam is causing the phenom? Anybody else had similar results and any ideas to fix issue?

No, not steam. If you are not using distilled water, you have deposits on the pin from impurities in the water. Why do you suspect steam? Is this a steam boiler?

Paul

Just under steam temps, so yea by the nature of it, should not be steam. Could be impurities as you said, but maybe it's still wet /connected as the pins are only about 15mm from each other. Maybe needs for distance between the two pins.

The way we used probes was to insulate the entire assembly with only the last couple of mm of each probe exposed.

I would expect condensation is happening at the top inside of the tank which is creating/keeping a “wet” path from your pin-across tank wall-other pin.

What material are your "pins" made out of? Does that material become a battery when combined with your tank?

Paul

You all bring up very good points. I will have to research this...probably get a clear polycarbonate boiler assembly to see exactly what is going on.

The pins are super high grade anti corrosion ss pins. I have yet to see e BBC en the slightest bit of corrosion on the pins so far. Makes me wonder why some people bother with less than accurate read systems like floats, capacitance, etc.

I will keep this post alive in the case I make good progress and find a good setup for it that works well in hot water. May be as easy as moving my pin much further away.

With your setup you can not reliably measure the actual water level - you can only really measure "tip inserted" or "tip not inserted". This as the resistance of water varies big time with the amount of minerals dissolved in it. Even small amounts of minerals will make your level measurement be very much off.

Make use of that property: if the resistance goes above a certain level it's not inserted, below another (lower) level and it's inserted. That's all you can tell. The short probe will tell you the tank is full (stop filling with water), the two long ones can tell you when it's empty (and time to start filling - and definitely switch off the heating element as it may have fallen dry).

If this is a hot water tank ( you mention steam) the simplest method is to fix temperature sensors strapped to the outside of the tank, under the jacket .
Hot water sits in layers so you should be able to detect the level of hot water or any hot/cold interface .
I have this setup on my domestic cylinder using thermistors and comparators - it’s run for 20 + yrs so far .
And ... any probe in contact with the water , running off a dc supply will corrode or gain metal due to electrolysis. It will also stay wet when the level drops