How can i learn soil moisture, humidity and temperature of soil?

[mustafauysal]

Hi
i am an engineering student. I have a project. I have to measure humidity, soil moisture and soil temperature wih a microcontroller. My instructor said that you should proof that your calculations are true. I can use these sensors. But my problem is, how can i proof that my measurements are true ?

 

[Clive]

calibration ?


ie soil moisture - weigh wet, oven-dry, weigh again = absolute soil moisture

temp - use a calibrated thermometer

 

[Kiwi Pete]

Do you mean calibrate your device?
Temperature is easy, use a couple of other temperature probes; humidity will be difficult, moisture content will require taking a measured sample and removing the moisture (weigh sample, dry in a low oven, reweigh, calculate loss of moisture = loss of weight)

 

[mustafauysal]

I don't mean calibrate actually. After i measue values, i should proof that they are real values. I think something like this will help me to see both soil moisture and humidity:
https://www.aliexpress.com/item/32806006405.html

 

[farmerm]

Is your project to build sensors from scratch and then then calibrate them? Or to take off the shelf sensors and program your controller to work with them. How precise do your measurements need to be?

As someone who uses soil moisture sensors, a lot, I can tell you the air humidity and temperature should be the easy bit. Are you looking to measure volumetric soil moisture using a capacitance type of sensor like a Sentek Envioscan sensor or a water potential sensor like the Decagon MPS2. As a general rule to create a calibration curve for a soil moisture sensor you need to take measured samples from as dry as you are able to achieve, from close to soil saturation and several points in between. As Kiwi Pete says above you then use the oven dry method to calculate the water volume of each.

The calibration curves will be different depending on the soil characteristics and the bulk density... Clay loam will be different from a coarse sand which in turn will be different from a silt or organic soil. Loose cultivate ground will measure differently to undisturbed soil deeper in the profile. How significant these variations are will depend on the sensitivity of your sensor and the application...

There are plenty of scientific papers online proving the accuracy of Sentek Enviroscan sensors and methodology behind establishing proof.

Research Papers - Sentek Technologies

Most research studies where soil or growing media is part of the study benefit from the insights gained from the dynamics of water movement and use in the soil.

sentektechnologies.com

 

[mustafauysal]

Is your project to build sensors from scratch and then then calibrate them? Or to take off the shelf sensors and program your controller to work with them. How precise do your measurements need to be?

As someone who uses soil moisture sensors, a lot, I can tell you the air humidity and temperature should be the easy bit. Are you looking to measure volumetric soil moisture using a capacitance type of sensor like a Sentek Envioscan sensor or a water potential sensor like the Decagon MPS2. As a general rule to create a calibration curve for a soil moisture sensor you need to take measured samples from as dry as you are able to achieve, from close to soil saturation and several points in between. As Kiwi Pete says above you then use the oven dry method to calculate the water volume of each.

The calibration curves will be different depending on the soil characteristics and the bulk density... Clay loam will be different from a coarse sand which in turn will be different from a silt or organic soil. Loose cultivate ground will measure differently to undisturbed soil deeper in the profile. How significant these variations are will depend on the sensitivity of your sensor and the application...

There are plenty of scientific papers online proving the accuracy of Sentek Enviroscan sensors and methodology behind establishing proof.

Research Papers - Sentek Technologies

Most research studies where soil or growing media is part of the study benefit from the insights gained from the dynamics of water movement and use in the soil.

sentektechnologies.com

Thanks for answer,
I will take off the shelf sensors. I don't need build sensors from scratch. my measurements don't need to be very precise. i would like to use something like this for soil moisture https://www.smart-prototyping.com/S...-Module-Soil-Moisture-Sensor-For-Arduino.html

 

[farmerm]

Thanks for answer,
I will take off the shelf sensors. I don't need build sensors from scratch. my measurements don't need to be very precise. i would like to use something like this for soil moisture https://www.smart-prototyping.com/S...-Module-Soil-Moisture-Sensor-For-Arduino.html

Wow that's a low cost sensor! You have to wonder how does any business survive making products like that unless of course they do what the Chineese do best, avoid the expense of actually doing real R&D, buy 1 genuine sensor, reverse engineer it and churn out low quality copies! But if you are happy to support such practices which ultimately will make it harder for electronic engineers in the UK to find jobs that is up to you... Proof that the output from that sensor is true would be as follows...

1) When the substrate is oven dry does the data says the substrate is dry?
2) When the substrate is saturated does the data say the substrate is saturated?
3) When the substrate is neither very dry or very wet does the data show it is neither very dry or very wet?

If answer to all 3 questions is yes then congratulations your measurements are true.

 

[farmerm]

also be aware water is not the only conductive medium in your substrate, difference soils can have different levels of conductivity and the addition of fertilisers and changes in temperature can also affect conductivity within the soil.

 

[mustafauysal]

also be aware water is not the only conductive medium in your substrate, difference soils can have different levels of conductivity and the addition of fertilisers and changes in temperature can also affect conductivity within the soil.

OK. thanks for answers

 

[glasshouse]

Sit on it