How to log the water level in a well pipe

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bastler11
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How to log the water level in a well pipe

#1 Post by bastler11 » 18 Apr 2021, 10:23

Hello everyone,

I would like to ask you for advice on how to solve the following problem: I would like to log the water level in a well pipe. Unfortunately, the pipe is not completely vertical, but rather curved. Therefore I cannot see the water level directly from above. The tube has a diameter of 24mm. The water level is in the moment 2,5m. In the summertime it is going down to about 3,5m. I measured the depth with a small bell on a tape. You can hear it when it is submerged in the water.

What kind of sensor could I use, electrical, mechanical or optical? Has anyone already carried out a depth measurement in such a pipe? Maybe, you have an idea?

Thanks and best regards!

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Re: How to log the water level in a well pipe

#2 Post by TD-er » 18 Apr 2021, 10:34

What material is this pipe made of?
If it is non-metal, then you could think of those "soil meters" which measure the soil to see if the plants need water by measuring capacitance.
These could then be taped at the outside of the pipe at specific places to measure whether there is water near it.

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Re: How to log the water level in a well pipe

#3 Post by bastler11 » 18 Apr 2021, 21:08

The pipe is made from PE, but it is in the earth. I only could only make any thing inside.

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Re: How to log the water level in a well pipe

#4 Post by TD-er » 18 Apr 2021, 21:29

24mm is a bit too small for an ultrasonic sensor.
I think the capacitive approach is still the best option, but maybe not by using the plant sensor things, but maybe constructing it from something similar to CAT5 cable.

A capacitor is just 2 plates close to each other, but not touching.
Water surrounding the plates affects the capacitance.
Just 2 wires parallel to each other doesn't have a lot of capacitance, but you can use the tightly twisted wires of CAT5.
There are 4 pairs of them, so you can consider them as 4 capacitors parallel.
Just make sure the ends that may touch the water will not conduct electricity, for example by creating a loop and on 1 end solder the ends of the wires together to 2 sets of 4 wires, each set containing only one of the twisted pairs.

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Re: How to log the water level in a well pipe

#5 Post by bastler11 » 19 Apr 2021, 07:20

The idea with the cable as a capacitor is good. I think if I take a cable from for example with 9m I can double the cable so that the two ends are on top. Than I have 4 plates and no isolation problem in the water.
To test it, I think I could take a similar 2m pipe which I fill with water.
But how could I get from the changing capacity a signal? How have I connect it at the esp? Or do I need an extra circuit?
Thanks and best regards.

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Re: How to log the water level in a well pipe

#6 Post by TD-er » 19 Apr 2021, 08:40

You can still use the circuit on one of those capacitive soil sensors.
Remember, the distance between the "plates" matters, so my first guess would be to use the two wires of a pair as opposite 'plates' of te capacitor.
But I don't know how the distance to water affects the capacitance.
In theory you should be able to measure an analogue value, depending on the amount of water surrounding the wire, but I guess the amount of water in the soil around the pipe may also affect the capacitance.

The principle to measure capacitance isn't that hard, but given you may have some unknowns it may need some tweaking.
The simplest way is to place a resistor in series with the capacitor and apply a voltage to it.
Then you measure the time it takes till the voltage over the capacitor is above some level.
If you have a multimeter that's capable of measuring capacitance, that would be a great start to prove the theory and get some idea of the effect of using multiple pairs in the cable.
Just keep in mind that your presence may affect the measurement as we humans are big bags of water.

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Re: How to log the water level in a well pipe

#7 Post by ingoiot » 19 Apr 2021, 19:12

capacitve sensors are pretty hard to tweak even with industry standard sensors.

what about a pressure sensor?

can you post a pic of the pipes shape?

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Re: How to log the water level in a well pipe

#8 Post by HomeJCL » 20 Apr 2021, 10:42

Pressure sensor in a 24 mm pipe will be tough and tube is not straight.

Possibility is Level with air pressure blanket, but not easy to have this on constantly as it needs an constant air flow and valve to put it on the smallest flow.

On the other hand do you need constant level ? This does not change a lot possibly.

If cable capacitor does not work, pressure sensor, some length of tubing till lowest point of level to be measured.
Small air pump (compatible pressure with water head) or big syringe and contraption/lever with servo

Rest is wiring and thinking how to build it.

Activation = 1 measuring cycle e.g.

This technique is most known for home use as pneumatic level indicator https://www.afriso.com/en/PM/Domestic- ... -gallery-5
Belgium and land of ESP ... counting :D

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Re: How to log the water level in a well pipe

#9 Post by bastler11 » 20 Apr 2021, 11:14

We had connected a pump to the well pipe until last year. Since the built-in filter was not fine enough and there was a lot of sand in the water, I drilled a new well and installed a special filter against very fine sand. In the old pipe I wanted to constantly log the groundwater level to see how it behaves depending on the season and the use of the new well. I have found this tof sensor https://www.christians-shop.de/GY-530-V ... 2_EALw_wcB and ordered me one. Maybe it is possible to measure the water level with it. I would mount it on the end of a 10mm thick pipe and then slide it 2m into the well pipe. Then I can record a change in height of max 2m.

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Re: How to log the water level in a well pipe

#10 Post by bastler11 » 20 Apr 2021, 11:16

Image
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Re: How to log the water level in a well pipe

#11 Post by Ath » 20 Apr 2021, 11:31

bastler11 wrote: 20 Apr 2021, 11:14 ... I have found this tof sensor https://www.christians-shop.de/GY-530-V ... 2_EALw_wcB and ordered me one. Maybe it is possible to measure the water level with it. ...
The plugin for the VL53L0X is available in ESPEasy (though not included in a standard build except the ESP32 MAX, that has all plugins included), but I haven't tried to use it inside a narrow pipe like you are now proposing. I'm very interested in seeing your results.
There is also an open PR for the VL53L1X sensor, that can measure up to 4 meters (where the VL53L0X allows ca. 2m). But if the pipe is not straight, measuring like that could be problematic.

In this forum post is a .bin file containing the VL53L0X plugin, but only in a ESP8266 4M1M configuration (and a couple of weeks old).
/Ton

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Re: How to log the water level in a well pipe

#12 Post by bastler11 » 20 Apr 2021, 11:54

I hope I will get soon the sensor to try it out😃.
Because of the not exactly vertical pipe, I hope that it will work if I position the sensor about 50cm above the highest water level.

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Re: How to log the water level in a well pipe

#13 Post by bastler11 » 20 Apr 2021, 13:33

@Ath

I have this build on my esp 8266 ESP_Easy_mega_20210223_normal_ESP8266_4M1M. So I have to update it?

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Re: How to log the water level in a well pipe

#14 Post by bastler11 » 20 Apr 2021, 13:42

Update is ready, so I have to wait for delivery 😃

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Re: How to log the water level in a well pipe

#15 Post by Ath » 20 Apr 2021, 15:50

bastler11 wrote: 20 Apr 2021, 13:33 I have this build on my esp 8266 ESP_Easy_mega_20210223_normal_ESP8266_4M1M. So I have to update it?
In that regular build the VL53L0X plugin is not available and neither will it be in any build, as it is not enabled in any configuration except ESP32 MAX, in that forum thread I made a custom-like build, including this plugin, so if you want to test that sensor you either have to make your own build or use that special build.
/Ton

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Re: How to log the water level in a well pipe

#16 Post by chromo23 » 21 Apr 2021, 22:41

first i would try a pressure sensor on a smaller pipe since you can convert the pressure directly into height

edit: the pressure sensor has the advantage over the tof sensor that it doesn’t need a line of sight. so the pipe can be crooked as much as it wants and for a moist environment it is definitely better suited

edit2: and it doesn’t need a special plugin if you are lucky because what you measure is resistance :)

edit3: and if it is only one point you want to measure us a mechanical pressure sensor with a switch

Edit: http://sites.prenninger.com/elektronik/ ... ndsanzeige
A lot of inspiration if you want to do it differently
Last edited by chromo23 on 22 Apr 2021, 10:07, edited 4 times in total.

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Re: How to log the water level in a well pipe

#17 Post by chromo23 » 21 Apr 2021, 23:01

e.g.:
Bildschirmfoto 2021-04-21 um 22.58.43.png
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there are different option for this sensor.
if you use the one from 0-30psi for example it is 1551,45mmhg ...thats 1,55m height you can measure in the pipe...

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Re: How to log the water level in a well pipe

#18 Post by TD-er » 21 Apr 2021, 23:09

When considering pressure, you could use a small tube which should always be under the lowest water level on one end and have a valve on the other end so you can blow air in it to empty the tube and then shut off the valve.
You can mount the pressure sensor on the end of a T-junction part (with the valve behind it)

Code: Select all

====T==|
    ^  ^
    1  2
	
1) position to place the pressure sensor (air tight)
2) the valve

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Re: How to log the water level in a well pipe

#19 Post by chromo23 » 21 Apr 2021, 23:13

or you put the pipe ready mounted with the sensor into the well when the waterlevel is at maximum...

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Re: How to log the water level in a well pipe

#20 Post by TD-er » 21 Apr 2021, 23:24

Problem is you could get some drift over time which is hard to correct for.
You can only measure pressure differences from whenever you close the tube with the sensor.

With a tube of specific length and creating over pressure you can always put it to the same level.

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Re: How to log the water level in a well pipe

#21 Post by chromo23 » 21 Apr 2021, 23:40

agreed but then i would make the pipe in a length where it is not submerged at the lowest point anymore. as an auto calibration so to speak

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Re: How to log the water level in a well pipe

#22 Post by bastler11 » 23 Apr 2021, 11:12

Good ideas!

To use the pressure sensor seems better, because of the high humidity in the well pipe.

So what I can do, I take the pressure sensor (which type is it?) and fix it at the end of a small pipe (see the picture). I do not know what is the lowest level. I checked now that there is a difference from about 1m. The actual min. level I have when I use the new well is about 3,5m. But I think during summe the level will go down? How much I don't know. If I use a pipe from about 4m I could measure the pressure difference from 2,5m to min 4,0m. If the level goes down more than 4m I would have the normal pressure in the pipe and I have to make the pipe longer. @chromo23 How do you mean auto calibration, when the water level is going down under the pipe length?

The next question is how to connect the sensor? I made an example circuit. Than I use the analog input from the esp8266. I don't know the Vcc and the resistance difference from the pressure sensor, the circuit is only an example. What do you think about it?
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Re: How to log the water level in a well pipe

#23 Post by TD-er » 23 Apr 2021, 11:37

You can also use simple sensors like the Bosch BMP280 or the BME280 if you also want to measure humidity.

One on the inside of the tube and one on the outside, so you can see the pressure difference regardless the weather.
Those Bosch sensors have very accurate pressure readings as I have had several of them on the same table and the reported pressure difference among all was less than 1 mbar.

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Re: How to log the water level in a well pipe

#24 Post by bastler11 » 23 Apr 2021, 12:03

Do you have also the type of the sensor in the picture ? The BMP280 is only on a circuit board available, because of the high humidity in the pipe is not so good?

What would be interesting is the temperature at about 80cm under the earth. It is the deep of our pipe from the toilet water cisterne to the house. Before several years the pipe was frozen.
May be the BMP680 would be interesting, but this is also on a circuit board. Are there any other designs?

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Re: How to log the water level in a well pipe

#25 Post by TD-er » 23 Apr 2021, 12:18

The chip itself is quite small, but also hard to solder by hand.
For temperature over a longer distance I would suggest to go for a Dallas sensor.
Those can also be had in water tight enclosures and can also be used with quite long cables.

For the BME/BMP sensor you can also wrap it in a plastic bag, but then it does not make sense to go for a BME version as the BMP is enough to measure pressure.
If you place a T junction on the tube, you can also go to a more wide diameter where you can place your sensor and make a flexible seal to keep the humidity out of that area as you are only interested in the pressure.

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Re: How to log the water level in a well pipe

#26 Post by bastler11 » 23 Apr 2021, 12:31

I found the pressure sensor at Amazon. It works for example from 0-30psi. Normal air pressure is about 15psi. If the small pipe with the sensor is 4m long and the level difference is about 2m the pressure difference is about 15psi. So it should work? Or is it better to take the 0-80psi sensor?

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Re: How to log the water level in a well pipe

#27 Post by bastler11 » 23 Apr 2021, 13:35

I think with this angeld auto hose valve it would be possible to press out the water in the pipe. But I'm not sure about the pressure measuring range.
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Re: How to log the water level in a well pipe

#28 Post by Ath » 23 Apr 2021, 13:55

bastler11 wrote: 23 Apr 2021, 13:35 ...But I'm not sure about the pressure measuring range.
According to Google, 1 meter of water causes a pressure of 1.4223 psi, so according to that a device that handles 0-30 psi, when the base pressure is 15, should be more than fine for your range, IMHO.
/Ton

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Re: How to log the water level in a well pipe

#29 Post by bastler11 » 23 Apr 2021, 15:09

Ok, but I do not measure the pressure in the water, I measure the pressure of the air in the pipe when the water level is changing. I take the sensor pipe in the well pipe and than I press the water with air out. That is than the zero point. If the water is going up the pressure of the air is rising. If the water is in the half pipe the pressure is double. So it is double of the zero point. And that means double of the normal air pressure? For this if I have a measure range of 0 - half pipe (2m). Than the max pressure is about 30psi? Is it right?

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Re: How to log the water level in a well pipe

#30 Post by TD-er » 23 Apr 2021, 15:17

By blocking the pipe you will increase pressure, but you will also affect the height change of the water level.
The water source is not a closed system, so by limiting air flow you will also limit the max. water level change inside the tube.
So what you are measuring is the pressure difference of the height of water surrounding your closed tube and since it isn't a straight tube, the pressure change will also not be linear.

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Re: How to log the water level in a well pipe

#31 Post by Ath » 23 Apr 2021, 15:25

Well, that ~1 meter of water is only going to compress for the length of the water inside the pipe, I would think, so if you would have 2 meters of water that would increase the pressure with 2x 1.4223 = 2.8446 psi. Doesn't look problematic to me when added to the base 15 psi.
That also explains the 'auto-recalibration' mentioned before. Once all water is out of the pipe, the outside and inside pressure will be equal, re-calibrating the setup :) except you won't know the actual level of the water, only that it is (probably) 'outside of measurable range'.

About linearity, I'd expect the non-linearity, and probably also the inaccuracy, of the sensor is about the amount of non-linearity of the pressure-change by a somewhat bent pipe, and won't be actually measurable by your pressure sensor.
/Ton

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Re: How to log the water level in a well pipe

#32 Post by bastler11 » 23 Apr 2021, 15:34

@ TD-er

Yes that's right.

Either I try to calibrate the system bevor outside with a similar pipe of water or I put the sensor down in the water. Than the pressure is linear with falling or rising water level. So the 0-30 psi sensor should be ok.

@Ath

When I press out the water in the pipe I think the pressure is not the normal air pressure. To press the water out I have to use higher pressure. So the pressure I need depends how high the water is in the pipe - right?

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Re: How to log the water level in a well pipe

#33 Post by TD-er » 23 Apr 2021, 15:35

The pressure you measure is linear with the height of the water column above the end point of the pipe filled with air.
Not the amount of water passed that point, but actually the height (Z-direction) of the water.

So you are not compressing the air inside the measurement tube a lot, you only compress it by the amount mentioned by Ath, 1.42 psi per meter of water height.

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Re: How to log the water level in a well pipe

#34 Post by TD-er » 23 Apr 2021, 15:37

bastler11 wrote: 23 Apr 2021, 15:34 When I press out the water in the pipe I think the pressure is not the normal air pressure. To press the water out I have to use higher pressure. So the pressure I need depends how high the water is in the pipe - right?
That pressure is exactly the same as what you need to pump up water into an open column over some height.

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Re: How to log the water level in a well pipe

#35 Post by bastler11 » 23 Apr 2021, 15:44

Yes, but than is there still the problem with linearity. Would the possibility to hang the sensor in the the well pipe at 4m not better? I only have to look that the connection to the short cable of the sensor is waterproof.

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Re: How to log the water level in a well pipe

#36 Post by Ath » 23 Apr 2021, 15:50

Usually with these kinds of setup, 'straight' linearity is assumed between the lowest and highest expected values by calibration. And also, how accurate do you need that level, probably not to 0.1 mm I would expect? :D
/Ton

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Re: How to log the water level in a well pipe

#37 Post by TD-er » 23 Apr 2021, 15:54

You have to ask yourself what you want to measure.
If you want to measure the amount of water in the tube, then the measurement with pressure is not linear.
But I guess you don't want to measure that but the height of ground water level and then measuring with pressure is linear to what you want to measure.
Also the initial capacitive method would then be non-linear to what you want to know.

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Re: How to log the water level in a well pipe

#38 Post by ingoiot » 23 Apr 2021, 19:28

only dutch and germans here but using PSI? really? ^^

one of this

should be sufficent. 0-2 bar is plenty range and enough resolution.

drop it down the pipe but take care of dirt and clogs.

for some extra money there are premade ones.

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Re: How to log the water level in a well pipe

#39 Post by Ath » 23 Apr 2021, 19:50

ingoiot wrote: 23 Apr 2021, 19:28 only dutch and germans here but using PSI? really? ^^
Guess us techy guys don't really mind what the unit of measurement is, it's an ESPEasy related question, so we'll bite :D :D :D
/Ton

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Re: How to log the water level in a well pipe

#40 Post by TD-er » 23 Apr 2021, 19:55

ingoiot wrote: 23 Apr 2021, 19:28 only dutch and germans here but using PSI? really? ^^
[...]
Nope, Dutch don't use PSI, but Google :)
I know it is a unit of measure for pressure, and it is the first table Google shows when searching for "pressure water column per meter"
No idea why Google thinks a unit based on inches makes sense when referring to height in meters, but I've seen a lot of strange things.

The weirdest one I know actually being used is "metric ton per cubic feet" (used in ship design)

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Re: How to log the water level in a well pipe

#41 Post by HomeJCL » 23 Apr 2021, 19:58

If you want to “plunge” something for a long time under water, IP68 is needed

So the first sensor with IP65 will need prepping to hopefully make it last.
Belgium and land of ESP ... counting :D

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Re: How to log the water level in a well pipe

#42 Post by chromo23 » 24 Apr 2021, 00:02

That also explains the 'auto-recalibration' mentioned before. Once all water is out of the pipe, the outside and inside pressure will be equal, re-calibrating the setup :) except you won't know the actual level of the water, only that it is (probably) 'outside of measurable range'.
thats what i meant.
I found the pressure sensor at Amazon. It works for example from 0-30psi. Normal air pressure is about 15psi. If the small pipe with the sensor is 4m long and the level difference is about 2m the pressure difference is about 15psi. So it should work? Or is it better to take the 0-80psi sensor?
depends on your height you want to measure and how you wanna do it.
but take the 80psi sensor.... your water level vary about 1,5m (would be 30psi) but maybe it gets slightly higher so you have some headroom
normal airpressure doesn’t take account because the sensor value is zeroed to the normal pressure.
so if your tube is empty you’ll measure 0 mmgh or 0 psi
and if it is 2m (2000mmgh) filled with water you’ll measure around 39 psi
and it is linear...
so at any given point (or known waterlevel) you can do a two point calibration of your resistance value.

https://de.wikipedia.org/wiki/Druck_(Ph ... ssigkeiten
the german wikipedia entry for pressure in fluids

edit:
only dutch and germans here but using PSI? really? ^^
i started it and never use it usually but it is the unit google gave me.... and since i use a overcomplex unit converter right now to type this text it really doesn´t matter
Nope, Dutch don't use PSI, but Google :)
:D

edit2:
@bastler11
don´t overthink the whole thing.....unless you want a waterlevel measurement that is accurate to the millimeter. i suspect you don’t need it that accurate.

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Re: How to log the water level in a well pipe

#43 Post by TD-er » 24 Apr 2021, 11:36

chromo23 wrote: 24 Apr 2021, 00:02 [...]
depends on your height you want to measure and how you wanna do it.
but take the 80psi sensor.... your water level vary about 1,5m (would be 30psi) but maybe it gets slightly higher so you have some headroom
normal airpressure doesn’t take account because the sensor value is zeroed to the normal pressure.
so if your tube is empty you’ll measure 0 mmgh or 0 psi
[...]
Nope, with empty tube with equal pressure to outside air pressure you are still at roughly 1000 mbar ;) (whatever that is in psi)
If the water level is covering the closed tube, the pressure will only be related to the extra pressure given by the height of the water column above the end point of the tube.

To quote wikipedia:
The pressure exerted by a column of liquid of height h and density ρ is given by the hydrostatic pressure equation p = ρgh, where g is the gravitational acceleration.
There are 2 constants: ρ & g
So it is only proportional to the height of the colum of water surrounding it.
Thus the pressure in the tube is the "default" pressure + the pressure of the water column.

So unless you will go over 10 meter deep, you should be able to use a 30 psi sensor.

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Re: How to log the water level in a well pipe

#44 Post by chromo23 » 24 Apr 2021, 18:04

Nope, with empty tube with equal pressure to outside air pressure you are still at roughly 1000 mbar ;) (whatever that is in psi)
that’s right... and if the sensor would measure a absolute value than you’d have to take that into account. but this sensor measures relative to the normal pressure. thats why your value would be zero(or whatever the value of the resistance is) at normal pressure (1000mbar)...

other than that... trial n error is always a good way to start unter those circumstances. the materials are cheap.. just a pipe and a sensor and an adapter...all of this you´ll need anyway so nothing can go wrong.
if you done it (successful or unsuccessful) i would be really happy if you’d share your experience.

bastler11
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Re: How to log the water level in a well pipe

#45 Post by bastler11 » 25 Apr 2021, 08:42

Sure, I will write down my experience here😃. Yesterday I ordered an additional pressure sensor. So I will have two options, pressure and the laser distance sensor.

In my example circuit from 23.04. I think I made a mistake. I made a new circuit. And I have to check that the max voltage is 1V.

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Re: How to log the water level in a well pipe

#46 Post by bastler11 » 25 Apr 2021, 09:47

Here is the circuit. I don't know the resistance from the pressure sensor, but I think I could take the voltage divider 1:5 or 1:10. Than I'm sure that the voltage at the ESP ADC is max. 1V.
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TD-er
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Re: How to log the water level in a well pipe

#47 Post by TD-er » 25 Apr 2021, 09:55

By adding such a parallel set of resistors you make the behavior non-linear.
I guess it is better to add one resistor in series with the resistor part of the potentiometer to make sure the max. voltage on the middle pin can get as high as your analog input may accept.
Remember that most ESP boards (except the ESP12 modules themselves) already have some voltage divider to extend the range from 0...1V to 0...3v3

And since your measured value will not change a lot, you might want to place some capacitor over the ADC input.
One 100nF to filter out high frequencies and one somewhere between 2 - 22 uF for the lower frequencies.
Place the 100nF as close as possible to the ADC input.

bastler11
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Re: How to log the water level in a well pipe

#48 Post by bastler11 » 25 Apr 2021, 10:23

Yes, you are right. But this I do not understand:
I guess it is better to add one resistor in series with the resistor part of the potentiometer to make sure the max. voltage on the middle pin can get as high as your analog input may accept.
I think I have to choose a load resistance witch is 10x Niger than the resistance from the pressure sensor. For this I have to check the resistance of the sensor.

The 100nf capacitor I should place direkt near the esp board (ADC - ground) and the 2-22uf for example at the output from the sensor to ground.

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Re: How to log the water level in a well pipe

#49 Post by TD-er » 25 Apr 2021, 11:58

The way you drawn it, it is a potentiometer, so the output voltage can change between max. and min position of the potentiometer.
So in your schematic it is max. 5V and min 0V.
The resistor in the potentiometer is constant, so by adding a resistor in series with it, between the potentiometer and the 5V you will limit the max output to some exact voltage.

If the sensor is not really a potentiometer, but only a variable resistor, then it is comparable to a potentiometer with only 2 pins connected (one of them the middle pin)
In that situation you still can place another resistor in series to limit the max. voltage.
If the max. resistance of the variable resistor is for example 10k, then the other resistor should be 40k to turn 5V to max. 1V.
Remember the highest voltage is then when the resistance of the variable resistor is maximal, it can get only lower.

The capacitor to filter out noise on the ADC should be placed between ADC and GND.

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Re: How to log the water level in a well pipe

#50 Post by bastler11 » 25 Apr 2021, 12:13

Ok, I don't know how the pressure sensor is build inside, it was only an idea from me. I will check it when I get the sensor.
The 100nF I place direkt near the ESP and the bigger capacity? Also there or better near the sensor?

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