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Article · December 23 doi: 10. 30871/jaic v7 6809 citations read authorsBog'liq 01#Повторная калибровка модельного емкостного датчика для измерения влажности почвы IoTII.
M
ETHOD
This research is quantitative research. Analysis was
conducted using primary data from gravimetric test
experiment on soil moisture sensors. Interactive web
dashboard system compiled using R Software. The steps of
this research are as follows:
1)
Build an Internet of things (IoT) based soil moisture
sensor. The process of measurement of soil moisture can be
seen via mobile phone through the Bynk application which is
connected to the internet.
2)
Perform a gravimetric test experiment. Instead of
using an oven, the soil is dried using 100 ml of 95% alcohol
for 100 ml of sun-dried soil samples. The number of data used
in this research is five, which comes from the level of increase
in water volume. The gravimetric test steps as follows.
Prepare 1000 ml of dry soil sample in a container
100 ml of soil sample was taken and then dried using
100 ml of 95% alcohol. The burning process was
carried out twice with 50 ml of 95% alcohol each. After
that, the soil sample was cooled and then its weight was
measured for Gravimetric Water Content
The next step is to measure the dry weight of the soil.
Measure and record soil moisture using an IoT-based
soil moisture sensor
Repeat steps c) & d) at increasing levels of water
volume, namely 100 ml, 200 ml, 300 ml and 400 ml.
Perform volumetric soil moisture content calculations
using equations (1) and (2)
3)
Modelling the gravimetric test results. Modelling
process performance evaluation using adjusted R Squares.
Modelling was carried out using linear and polynomial
regression model in R stat package [7].
4)
Set up Re-calibration Application. The re-calibration
application uses the R shiny package in the R application [8].
5)
Assemble a model-based capacitive soil moisture
sensor system. The model coefficients resulting from the re-
calibration are then programmed into the Arduino.
A. Gravimetric Test
Gravimetry is a method of determining soil moisture. The
soil moisture sensor is calibrated based on gravimetric results
on soil samples before being installed in the field. After
weighing the fresh weight, the samples were dried at 105 ºC.
Soil water content is determined using the equation
𝜃
𝑔
=
(
𝑚
𝑤𝑒𝑡
−𝑚
𝑑𝑟𝑦
)
𝑚
𝑑𝑟𝑦
(1)
Where,
𝜃
𝑔
is the gravimetric soil moisture content,
𝑚
𝑤𝑒𝑡
and
𝑚
𝑑𝑟𝑦
is the fresh and dry weight of soil (g). The gravimetric
soil moisture content was converted to volumetric soil
moisture content using
𝜃
𝑣
=
𝜃
𝑔
𝑥 𝜌
𝑠𝑜𝑖𝑙
𝜌
𝑤𝑎𝑡𝑒𝑟
(2)
Where,
𝜃
𝑣
is the volumetric soil moisture content,
𝜌
𝑠𝑜𝑖𝑙
and
𝜌
𝑤𝑎𝑡𝑒𝑟
are soil and water density.
𝜌
𝑤𝑎𝑡𝑒𝑟
= 1 𝑔𝑐𝑚
−3
. The digital
value that the sensor observes varies by sensor type. Linear,
quadratic and exponential relationship patterns can be found
between the volumetric soil water content and the sensor
digital value. The greater the coefficient of determination, the
better the relationship pattern obtained. [9]
Gravimetric test is one of the most frequently used tests in
soil moisture sensor calibration. The concept of the
gravimetric test is that the moisture sensor is able to follow
changes for the increasing of water volume in previously
dried soil. Some of the studies using the Gravimetric test are
as follows.
T
ABLE
1.
P
REVIOUS RESEARCH ON THE GRAVIMETRIC TEST
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