Enhancing the Accuracy of the Low-Cost Capacitive Soil Moisture Sensor SEN0193 for Internet of Things Applications

Genovez, Jorge Gabriel Fernandes; Gripp, Anderson da Rocha; Duque, Ana Clara de Lemos Pinto; Felix, Rodrigo Weber; Esteves, Francisco de Assis; Martins, Rodrigo Lemes

doi:10.1590/1678-4324-2025240380

Article - Engineering, Technology and Techniques • Braz. arch. biol. technol. 68 • 2025 • https://doi.org/10.1590/1678-4324-2025240380 linkcopy

Enhancing the Accuracy of the Low-Cost Capacitive Soil Moisture Sensor SEN0193 for Internet of Things Applications

Authorship SCIMAGO INSTITUTIONS RANKINGS

Monitoring soil moisture is an essential aspect of comprehending the functioning of terrestrial ecosystems. However, the cost of commercial sensors often challenges their acquisition. In response to this issue, manufacturers have developed several low-cost soil moisture sensors in recent decades, but there is still a need to improve the evaluation of their precision and accuracy. This article assesses the precision and accuracy of a low-cost soil moisture sensor SEN0193. The assessment results highlight the consistent precision of SEN0193 and emphasize the homogeneity of responses among sensors of the same model. The study also underscores the significant impact of soil granulometry on sensor precision, emphasizing the importance of realizing site-specific calibrations. In terms of accuracy, the study reveals that the calibration recommended by the manufacturer tends to overestimate moisture, particularly in soils with smaller granulometry. The study suggests that soil-specific calibration methods utilizing linear equations are more reliable and effective than polynomial and exponential approaches, especially when employing three to five calibration points. This study offers an essential contribution to the advancement of accessible methods for soil moisture monitoring. These methods are crucial for efficiently monitoring soil moisture in agriculture and natural ecosystems.

Keywords:
calibration; precision; smart agriculture; soil water content.

Our study has validated the precision of the SEN0193 sensor.

Manufacturer calibration of the SEN0193 exhibited low accuracy.

We recommend a two-point linear calibration considering soil-specific characteristics.

Water content (ml)	Factors	Df	Sum Sq	Mean Sq	F-value (or KW-value)	P-value
0	Sensors	8	123.8	15.481	2.223	0.0759
	Residuals	18	125.3	6.963	-	-
5	Sensors	8	-	-	3.632	0.8887
	Residuals	18	-	-	-	-
10	Sensors	8	-	-	3.764	0.8777
	Residuals	18	-	-	-	-
15	Sensors	8	-	-	3.764	0.9313
	Residuals	18	-	-	-	-
20	Sensors	8	756	94.5	0.037	0.999
	Residuals	18	45995	2555.3	-	-
25	Sensors	8	2449	306.2	0.485	0.851
	Residuals	18	11355	630.8	-	-
30	Sensors	8	-	-	4.0407	0.8534
	Residuals	18	-	-	-	-
35	Sensors	8	-	-	5.3395	0.7208
	Residuals	18	-	-	-	-

Water content (ml)	Factors	Df	Sum Sq	Mean Sq	F-value	P-value
0	Grains	2	2.74	1.37	0.133	0.876
	Residuals	24	246.44	10.27	-	-
5	Grains	2	12350	6175	67.28	< 0.001
	Residuals	24	2203	92	-	-
10	Grains	2	32035	16017	103.5	< 0.001
	Residuals	24	3714	155	-	-
15	Grains	2	25505	12753	118.8	< 0.001
	Residuals	24	2576	107	-	-
20	Grains	2	43102	21551	141.7	< 0.001
	Residuals	24	3649	152	-	-
25	Grains	2	9379	4690	25.43	< 0.001
	Residuals	24	4426	184	-	-
30	Grains	2	9526	4763	61.73	< 0.001
	Residuals	24	1852	77	-	-
35	Grains	2	3911	1955.6	22.81	< 0.001
	Residuals	24	2058	85.7	-	-

Grain sized	Manufacturer calibration		Site-specific calibration
Grain sized	MBE	R²	MBE	R²
Coarse	30.1 ± 4.44^a,A	0.51 ± 0.05^a,A	14.8 ± 1.26^b,A	0.73 ± 0.04^b,A
Medium	34.3 ± 4.60^a,AB	0.47 ± 0.04^a,AB	14.0 ± 1.26^b,A	0.76 ± 0.05^b,A
Fine	41.6 ± 5.14^a,B	0.43 ± 0.04^a,B	15.5 ± 1.29^b,A	0.73 ± 0.04^b,A

Grain sized	CP	Linear		Polynomial		Exponential
Grain sized	CP	MBE	R²	MBE	R²	MBE	R²
Coarse	3	7.97 ± 1.78^a,A,1	0.87 ± 0.04^a,A,1	0.94 ± 16.7^a,A,1	0.76 ± 0.19^ab,A,1	5.18 ± 8.53^a,A,1	0.75 ± 0.1^b,A,1
	4	2.51 ± 0.82^a,AB,2	0.92 ± 0.02^a,A,2	-2.66 ± 12.5^a,A,1	0.86 ± 0.10^ab,A,1	-0.75 ± 7.53^a,A,1	0.8 ± 0.06^b,AB,1
	5	3.18 ± 0.94^a,A,2	0.92 ± 0.02^a,A,2	3.11 ± 14.6^a,A,1	0.78 ± 0.14^b,A,1	4.53 ± 8.02^a,A,1	0.78 ± 0.08^b,A1
Medium	3	6.19 ± 1.04^a,AB,1	0.88 ± 0.02^a,A,1	-1.3 ± 7.13^a,A,1	0.88 ± 0.06^a,A,1	3.73 ± 7.92^a,A,1	0.76 ± 0.06^b,A,1
	4	3.68 ± 1.08^a,A,2	0.9 ± 0.02^a,AB,2	4.11 ± 10.5^a,A,1	0.84 ± 0.06^ab,A,1	6.47 ± 10.5^a,A,1	0.75 ± 0.1^b,A,1
	5	3.13 ± 0.68^a,A,2	0.9 ± 0.02^a,AB,12	5.96 ± 9.17^a,A,1	0.8 ± 0.18^ab,AB,1	0.52 ± 4.38^a,A,1	0.8 ± 0.04^b,AB,1
Fine	3	5.52 ± 1.10^a,B,1	0.86 ± 0.03^a,A,1	-3.11 ± 10.1^a,A,1	0.87 ± 0.06^a,A,1	-1.07 ± 7.23^a,A,1	0.86 ± 0.02^a,B,1
	4	1.22 ± 0.85^a,B,2	0.89 ± 0.02^a,B,2	1.08 ± 12.5^a,A,1	0.83 ± 0.15^a,A,1	3.44 ± 7.03^a,A,1	0.85 ± 0.07^a,B,1
	5	1.99 ± 0.63^a,B,2	0.89 ± 0.02^a,B,2	-5.44 ± 11^a,A,1	0.87 ± 0.09^a,B,1	0.38 ± 5.59^a,A,1	0.88 ± 0.05^a,B,1

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Instituto de Tecnologia do Paraná - Tecpar Rua Prof. Algacyr Munhoz Mader, 3775 - CIC, 81350-010 , Tel: +55 41 3316-3054 - Curitiba - PR - Brazil
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