Swimming pool level detection

dr pepper said:

Makes sense, would temp affect the oil's mass?

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Yes but I have no idea how much. The guys who set up level monitoring on a tank of for example #2 heating oil would know the correction factors and how much they matter. Pure water has a specific gravity of 1.000 at about 50 degrees F. I know with standard atmospheric pressure of 14.5 PSIG (29.5223 inches of HG) a water column in a tank of 27.7076 (call it 27.7) inches will be 1 PSIG of pressure. I believe that is based on a water temperature of 4 degrees C or 39.2 degrees F. While I know that heating oil, like water will expand with increasing temperature I have no clue how much or how many inches of fuel oil column would be equal TO 1.0 psig. beats me?

Ron

dr pepper said:

would temp affect the oil's mass?

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No, but it would affect the oil's density. So if the container had the same cross-sectional area throughout its height, an x% reduction in density would cause an x% increase in level.

alec_t said:

No, but it would affect the oil's density. So if the container had the same cross-sectional area throughout its height, an x% reduction in density would cause an x% increase in level.

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.. .. .. and it would be quite unpleasant for swimming in ?

S

Here https://www.ti.com/lit/ug/tidu736a/tidu736a.pdf is an interesting level senor design from TI.

Musicmanager said:

and it would be quite unpleasant for swimming in ?

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Guess so. It could also be difficult, given the lower buoyancy and increased viscosity, compared to water.

KeepItSimpleStupid said:

Here https://www.ti.com/lit/ug/tidu736a/tidu736a.pdf is an interesting level senor design from TI.

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Pretty slick sensor'

Ron

If I understand you well, you had the foil in the pipe isolated from the water and the piece of wire exposed to the water? At what frequency and voltage did you run the sensor?
yes exactly , 5v i forget frequency exactly ... id have to dig up code if ur interested

... ohya, i put one side of the cap to the analog pin, and the other side on a digital output pin ....
so when the analoug hit a thresh hold it would switch the digital pin polarity , and read the time delay on both slopes

Of course density not mass that remains constant.
The guage came with instructions, there was no mention of a temp sensor, the sense line to the tank is just a nylon tube.
I assume then temp makes little difference to the readings, if it has a temp sensor in the display unit it'll be miles out as the display is in the boiler house which is 30 degrees all the time, the oil is outside and can be -10.
I think if you tried to swim in there you wouldnt be comming out again.

Alot of pics come with a cap touch sensor built into the chip, i use them for water level detection in humidity chambers. Microchip designed them for reading contactless touch switches, they are basically an accurate current source that charges a known capacitor in the chip. The 18F chips with them in have a fair amount of settings to tweak them, they are ideal for water sensors and hardly any hard where needed.

The humidity chamber i use, or more accurately environment chambers use ultrasonic misting to increase humidity. These devices are like the things you buy for lizards etc, they have one big problem in so much as they need an accurate water level to work properly, you get around 25mm in level difference before they stop making a dry water mist. I turn the container with the water in into a capacitor, just foil on the outside really. Works well with the sap touch pics.

Sort of related. Several years ago I made a automated water filling system for a Christmas tree stand. Mine used three 316 stainless steel TIG filler rods. To prevent corrosion the electrode assembly was driven with an AC signal. The two level signals were rectified and fed to a microcontroller's inputs. The output was used to drive an SSR that controlled a small fountain pump. DC electrodes result in electrolytic corrosion. I only use it for a month and a half each year with tap water, but see no change in the electrodes' surface. If I ever saw any I would just change the wires. It serves the same function as your pool system.

https://www.picaxeforum.co.uk/showthread.php?12266-08M-Christmas-tree-watering-controller
https://www.picaxeforum.co.uk/showthread.php?12266-08M-Christmas-tree-watering-controller
Ken