Moisture meter vs. blood pressure monitor

Organize and arrange your garden and vegetable garden: ornamental, landscape, wild garden, materials, fruits and vegetables, vegetable garden, natural fertilizers, shelters, pools or natural swimming pool. lifetime plants and crops in your garden.
izentrop
Econologue expert
Econologue expert
posts: 13644
Registration: 17/03/14, 23:42
Location: picardie
x 1502
Contact :

Re: Moisture meter vs. blood pressure monitor




by izentrop » 08/06/21, 09:40

Uncle Buzz wrote:The measurements do not depend on the terrain, this is precisely the main interest of blood pressure monitors
How do you explain that then :?:
Attachments
tensiometer.gif
tensiometre.gif (46.89 KiB) Viewed 2939 times
0 x
User avatar
Did67
Moderator
Moderator
posts: 20362
Registration: 20/01/08, 16:34
Location: Alsace
x 8685

Re: Moisture meter vs. blood pressure monitor




by Did67 » 08/06/21, 10:10

Uncle Buzz wrote:
There is no such thing as a perfect and durable seal, this is the most difficult point to obtain, especially if you tinker with something to transform it. This is the drawback of tensiometers, they must remain filled with water, and no leakage allows air to replace the water while the soil sucks it in.



Yes, at this level, "perfect" would be overkill. And is not necessary. But it has to last a few days ...

A small "bubble" of air does not change anything, as long as there is water at the bulb level ... So a long rod is more convenient. There is more “reserve” of water. ”That said, when the bubble increases in size, due to its elasticity, it takes more and more volume!

On the Stelzner, in fact, it is the O-ring under the pressure gauge which is the sensitive part. By dint of crushing it ... But it can be found in boxes of 50 in any DIY store. Little by little, over a month, there is air coming in ... But the indication remains.
0 x
User avatar
Did67
Moderator
Moderator
posts: 20362
Registration: 20/01/08, 16:34
Location: Alsace
x 8685

Re: Moisture meter vs. blood pressure monitor




by Did67 » 08/06/21, 10:33

izentrop wrote:
Uncle Buzz wrote:The measurements do not depend on the terrain, this is precisely the main interest of blood pressure monitors
How do you explain that then :?:


These graphics are real puzzles. For interpretation.

Uncle Buzz talks about measurement. Voltage measurement. So a measure of the force with which the soil retains water. And he's right: it doesn't depend on the ground! The water can be at - 200 mbar in any type of soil!

The graphics try to "translate" the links between this tension and the quantity of water then contained in the soil. And there, the difference is enormous: in a sandy soil, for such tension, there is very little water, whereas in a clayey soil, there is a lot.

And a second difference is enormous: at the "maximum" tension that plants can develop, some soils no longer contain much, while others still contain a lot. But it is useless!

And there, we see that the curves are very clearly different.

And consequently the "useful reserves" (black zones), which are the difference between the quantity of water that the soil retains after being drained (therefore the water which occupies the "macroporosity" - the big holes - s' is removed, leaving room for the air) = "soaking point" and that which it still contains when the plants can no longer extract it (the water is then too strongly retained by the fine particles - as the 12% water that is in the flour and that nobody "sees"!) = point of wilting.

Basically, this usable water normally occupies the "microporosity" of the soil. Basically, it's like the capillary action in a piece of sugar: when you steep it, the coffee "rises". This coffee would be withheld if the piece did not melt. If we soaked the piece, more coffee would come in. And when we take it out, a few drops would flow first. It is the soaking.

The richer a soil is in fine particles ('clays), the greater this final quantity of water. Hence the trap: clay soils certainly retain a lot of water, but keep too much! They don't have the best RU !!!

A silt is quite similar to a piece of sugar. A clod of loamy soil. Lots of microporosity and therefore capillarity. But less total surface of the particles, those which "trap" the water in the clays.
0 x
Uncle Buzz
I understand econologic
I understand econologic
posts: 102
Registration: 30/10/19, 20:06
x 24

Re: Moisture meter vs. blood pressure monitor




by Uncle Buzz » 08/06/21, 10:42

If you look closely, you see on the y-axis scale on the left (mbar) that the points are the same whatever the soil, what changes, however, is the soil moisture rate in% on the scale abscissas.
The values ​​in mbar are the same on the 3 types of soil, the humidity rate is very different.
The sand retains water weakly, it stores much less suddenly (the graph does not show more than 40%), the soil tension remains low until around 10%.
In clay, at 40% humidity the tension already rises quickly, there is much more water in the soil than in the sand, but it is retained more strongly by the clay.
1 x
Uncle Buzz
I understand econologic
I understand econologic
posts: 102
Registration: 30/10/19, 20:06
x 24

Re: Moisture meter vs. blood pressure monitor




by Uncle Buzz » 08/06/21, 11:03

Did67 wrote:A small "bubble" of air does not change anything, as long as there is water at the bulb level ... So a long stem is more


As little air as possible is needed, because as the air is compressible, its volume increases and decreases according to the pressure, suddenly the ground can suck up a volume of water which comes out of the tensiometer which will be occupied by the volume of 'air which increases, conversely when the ground receives water again (rain or watering) the depression of the tensiometer then sucks the water from the ground which returns again and fills the volume that the air gives up by being "compressed".
The concern is that coming and going through the porous head can reduce its porosity by blocking it little by little and we lose sensitivity (speed of variation, but hey we are dealing with very slow movements, a few measurements per day big max is enough if we want to do "real time" monitoring, 1 time per day is enough to know if there is a need to water, if we have 1 hour of lag with reality that does not pose really a problem, but in the long run, the ceramic head can be plugged.
0 x
izentrop
Econologue expert
Econologue expert
posts: 13644
Registration: 17/03/14, 23:42
Location: picardie
x 1502
Contact :

Re: Moisture meter vs. blood pressure monitor




by izentrop » 08/06/21, 16:03

Uncle Buzz wrote:You can divert watering "carrots", the difficulty is the tightness, because at 700mbar, it sucks hard and there is the risk of emptying the tensiometer.

I did some to validate the feasibility (it works), I must now re-study them to make them more reliable (held in time) but in my case it involves the realization of a printed circuit (the study, I have the manufacturing by a prototyping service: oshpark) soldering of SMD components (requires a little tooling because it is really tiny) and programming because I use digital sensors, with radio transmission.
You do that cheap:
A pressure sensor recovered from a washing machine, some are adjustable.
Personalizedsmall modules of this type for transmission up to fifty meters
A box with battery (consumption only when the order is transmitted)
Uncle Buzz wrote:If you look closely, you see on the y-axis scale on the left (mbar) that the points are the same whatever the soil, what changes, however, is the soil moisture rate in% on the scale abscissas.
It's clear :P ... I had not put my 8)
0 x
User avatar
Rust COHLE
I understand econologic
I understand econologic
posts: 110
Registration: 23/11/20, 14:37
Location: Mediterranean-mountain 450m
x 12

Re: Moisture meter vs. blood pressure monitor




by Rust COHLE » 20/06/21, 21:37

Did67 wrote:
izentrop wrote:
Uncle Buzz wrote:The measurements do not depend on the terrain, this is precisely the main interest of blood pressure monitors
How do you explain that then :?:


These graphics are real puzzles. For interpretation.

Uncle Buzz talks about measurement. Voltage measurement. So a measure of the force with which the soil retains water. And he's right: it doesn't depend on the ground! The water can be at - 200 mbar in any type of soil!

The graphics try to "translate" the links between this tension and the quantity of water then contained in the soil. And there, the difference is enormous: in a sandy soil, for such tension, there is very little water, whereas in a clayey soil, there is a lot.

And a second difference is enormous: at the "maximum" tension that plants can develop, some soils no longer contain much, while others still contain a lot. But it is useless!

And there, we see that the curves are very clearly different.

And consequently the "useful reserves" (black zones), which are the difference between the quantity of water that the soil retains after being drained (therefore the water which occupies the "macroporosity" - the big holes - s' is removed, leaving room for the air) = "soaking point" and that which it still contains when the plants can no longer extract it (the water is then too strongly retained by the fine particles - as the 12% water that is in the flour and that nobody "sees"!) = point of wilting.

Basically, this usable water normally occupies the "microporosity" of the soil. Basically, it's like the capillary action in a piece of sugar: when you steep it, the coffee "rises". This coffee would be withheld if the piece did not melt. If we soaked the piece, more coffee would come in. And when we take it out, a few drops would flow first. It is the soaking.

The richer a soil is in fine particles ('clays), the greater this final quantity of water. Hence the trap: clay soils certainly retain a lot of water, but keep too much! They don't have the best RU !!!

A silt is quite similar to a piece of sugar. A clod of loamy soil. Lots of microporosity and therefore capillarity. But less total surface of the particles, those which "trap" the water in the clays.


Thank you all I enjoy reading all these details on the blood pressure monitor while I am not stuck on the question, but Didier or another person: how did you or would you do to determine the measurement to be taken into account on the mano of the Stelzner according to the characteristics of its soil following analysis?
I would like to leave one permanently in the summer in the greenhouse in the same place and another outside what do you think? Or should they be removed after each use?
My vegetables thank you through me, they are starting to get thirsty!
This time it is I who thank you if you have the time and the inclination to answer me!
0 x
"Efficiency is intelligent laziness"

Back to "Garden: landscaping, plants, garden, ponds and pools"

Who is online ?

Users browsing this forum : No registered users and 102 guests