With the wide variety of soil water content sensors in the market, it is such a challenging task to seek the best water sensor that can be suitable for the application you need and can lead to confusion.
To understand this, it is vital that you know what the water content sensor really gauge and what is the features and specification of the soil water content sensor that the makers are offering because you might be surprised to realize that there isn't any soil water content that can directly gauge the water.
The water sensors will just determine the changes in soil property in which related to the water content, instead, such as the permittivity of dielectric, conductivity of the thermal and the neutron flux density. These dielectric permittivity sensors are the common kinds of sensors that are available which utilizes varied technology in order to gauge the permittivity of the soil like the time domain in reflectometry and transmissivity, the line oscillation transmission, the charge capacitance time, the domain reflectometry frequency, and the coaxial different of amplitude reflectometry, as well as the dielectric reflectometry.
No matter what the technology of the sensor it still applies the same principles that changes will be relative to the dielectric permittivity with the volume of water. Permittivity in a simple and common way is the stored energy, it is which the sensor will try to detect in the soil because the molecule of water is polar and unbound molecules of water is related to the electric line field, so the more volume of water presence in the soil, the higher the energy and the bulk permittivity in the soil.
Water isn't all that consist of in soil, there are minerals and organics and air because of this, some soil water content sensor converts the sensor's electric results to the volume of the water but no matter what the sensor will do, this will affect how it shall calculate the electric output.
So, how will you know that the soil water content sensor is good enough? To answer this, a sensor has all the capacity to:
1. get the required accuracy
2. should be durable and last long
3. with little calibration or no recalibration needed
4. cost effective or budget friendly
5. easy to use, measure and install
However, you might not get all these capabilities in one sensor, so in another way to seek for what is a right sensor for you, you must weigh which capacity or feature you need out of your sensor.
Sometimes the sensor makers too will out on specifications that you might not well understand. The accuracy measurement is really determined relative to the water content, dielectric permittivity and the signal of electric in the soil such the accuracy of the water content is gauge base on the electrical measurement, temperature effects and etc.
If only every sensor available in the market will give accuracy features on its packages with regard to how it measures the permittivity, then it is easy to make a comparison with their performance. However, this is not the case, some sensor makers will choose other specifications to showcase in the sensor marketing so be warned for the specification or features of the sensor that tells it has a high accuracy because accuracy is dependent to various consideration.
On the other hand, the resolution is the amount of soil water content needed to transform or change before a soil water sensor can predict the change. This is usually done by measuring the electric out from the sensor measurement and the high-performance sensor will positively give out high accuracy and resolution.
Another thing must not be overlooked too is the range measurement of the sensor because the range measurement will vary depending on the soil type so, make sure the sensor will give range to the soil type you have. The fact is, there is really no ideal and best soil water content sensor, only choose the features for the application you need and if you understand well what the sensor is actually measuring you can get the best perfect for your need.
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