Moisture meter vs. blood pressure monitor

[Did67]

that that I ordered is simple, here is one with 2 probes that works on the same principle

It's that guy. I do not know on what principle it is based:

[izentrop]

Your link does not work, or amazon is blocked by the forum.
it must be this model
There are not too many unhappy people, you may have fallen out badly and you should have asked for an exchange.

The probe also appears to be galvanic. I wonder how, with the same probe, they differentiate between PH and humidity?

[Did67]

There are not too many unhappy people, you may have fallen out badly and you should have asked for an exchange.

The probe also appears to be galvanic. I wonder how, with the same probe, they differentiate between PH and humidity?

I made the simpler hypothesis, and nevertheless credible, that when we do not know anything about it, we above all need an answer ... It is not a question of acting with precision, it is a question of to calm the worry "should I water?" ... It is clear that in "dry" soil (apparently), the conductivity must drop, the "gadget" indicates "Dry", we watered ... and it grows. We would water without gadget, it would grow. And we would put our finger on it, we would say to ourselves "hey, it's dry, I'm going to water" - and it would grow!

In my watering management, I want to know if I am near the "wilting point" or not ... 4 days after a heavy rain, my soil is "dry". Judgment. And the probe indicates "Dry". I take a spade, and I guarantee you that we are VERY far from the withering point. So we often water "for nothing" ... But if we "believe" in the contraption, of course we are satisfied! It grows!

[Uncle Buzz]

This type of probe is one shot, instantaneous measurement, you immerse your probe, you read a measurement, you remove your probe. There is no question of leaving it permanently in the ground and having a follow-up because the metal parts will oxidize and lose sensitivity.

In addition, on a "constant" soil we can compare the measurements, but from one soil to another, or even the same soil but with variation in mineral salts or other soluble elements creating ions during fertilizer input ( rapid modification) or decomposition of organic matter (slow modification) we change the measurement for the same humidity rate which makes them probes which give an idea of ​​the order of magnitude of the humidity but which are not reliable for to measure.

For the management of water in your garden, with a little learning I think it can be quite suitable, you just have to know the limitations.

[izentrop]

So, nothing beats that https://agritrop.cirad.fr/479524/1/document_479524.pdf

If not, does the DIY blood pressure monitor exist?

[Did67]

If not, does the DIY blood pressure monitor exist?

You take a very small "oya", you adapt a threaded tube, you find a pressure gauge which measures sufficiently precisely depressions up to 1 bar, you manage to hold everything together and make it watertight, and you have a blood pressure monitor ...

If you have access to clays having a granulo allowing to give, by firing, a sufficiently porous head (the clays of the potters often give "terracotta" little porous, therefore the system will not react well), you can "mold" all ...

[Uncle Buzz]

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.

But for a direct reading, a manometer is enough when we can seal everything, but interest in commercial blood pressure monitors is limited. I took a blumat as a reference and for 35 € it works well, but it is manual reading is punctual, we do not all need regular monitoring 24/24 7/7 ...

[Did67]

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.

Yes indeed. The "carrot" is a porous capsule!

But I do not understand: if the circuit is waterproof (and it must be), there is necessarily a balance between the force with which the water is sucked from the tensio towards the ground and that with which it is retained by mano "resistance" - this is what allows the mano to measure the force with which water is held in the ground. In fact, in a tensio, very little water "comes out". Immediately, depression is formed and the forces are balanced. And so she doesn't go out anymore

You need of course a piece of tube above the carrot, to have a little water in reserve.

[izentrop]

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.

But for a direct reading, a manometer is enough when we can seal everything, but interest in commercial blood pressure monitors is limited. I took a blumat as a reference and for 35 € it works well, but it is manual reading is punctual, we do not all need regular monitoring 24/24 7/7 ...

I notice that it requires a lot of maintenance and the measurements also depend on the type of terrain https://asset.conrad.com/media10/add/16 ... r-8059.pdf

Making an automatic watering trigger system seems more feasible to me with a capacitive or resistive probe.

[Uncle Buzz]

But I do not understand: if the circuit is waterproof (and it must be), there is necessarily a balance between the force with which the water is sucked from the tensio towards the ground and that with which it is retained by the "resistance" of the mano

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.

Even purchased blood pressure monitors may not be completely waterproof depending on handling, if the cap is not properly served, if an O-ring dries out over time ...
Besides the risk of frost in winter, a 100% electronic sensor is more reliable over time, with some corrections depending on the type of soil.
Reflectometry is used by professionals, it is technically "simple" in principle, which is not, however, it is electronic production because the measurement speeds are much higher than what basic electronics allow. that an individual hobbyist can use.

I notice that it requires a lot of maintenance and the measurements also depend on the type of terrain https://asset.conrad.com/media10/add/16 ... r-8059.pdf

Making an automatic watering trigger system seems more feasible to me with a capacitive or resistive probe.

The measurements do not depend on the terrain, this is precisely the main interest of tensiometers, it really measures the availability of water for plants. The wilting point is the same regardless of the soil, when the soil retains too much water for the plant to use, no matter whether it is sand or clay, the tension is the same, in however what changes is the quantity of water in the soil (humidity level) and therefore the watering must take into account the type of soil because at a given voltage, the remaining water reserve for the plants is not not the same.