XXX-X-XXXX-XXXX-X/XX/$XX.00 ©20XX IEEE Unmilled Rice Moisture Content Sensor for Rice Mill Factory Applications Somporn Seewattanapon Faculty of Engineering and Architecture, Rajamangala University of Technology Suvarnabhumi, Nonthaburi, Thailand somporn.s@rmutsb.ac.th Nonchanutt Chudpooti Department of Industrial Physics and Medical Instrumentation, Faculty of Applied Science, King Mongkut’s University of Technology North Bangkok, Bangkok, 10800 Thailand nonchanutt.c@sci.kmutnb.ac.th Prayoot Akkaraekthalin Departmemnt of Electrical and Computer Engineering, Faculty of Engineering, King Mongkut’s University of Technology North Bangkok, Bangkok , Thailand prayoot.a@eng.kmutnb.ac.th Abstract— This research presents a novel electromagnetic- based sensor for inline measurement of unmilled rice paddy moisture content in the rice mill factory. The proposed sensor has been designed based on the modified planar dipole structure at the operating frequency of 440 MHz. The unmilled rice dielectric constant properties have been studied and applied for characterizing the moisture content. The unmilled rice moisture content sensor system then has been designed consisting of the proposed sensor, a microwave signal generator, a microwave signal detector, and a microcontroller. The moisture content sensor system has been implemented and used for measuring the unmilled rice paddy moisture content in a real rice mill factory in Udon Thani province, Thailand. When compared with the commercial rice moisture content tool based on a capacitance technique, the proposed rice moisture content sensor system gives almost same results, which only about 4% difference has been found. Keywords— Moisture content sensor, dielectric constant measurement, agricultural sensor, unmilled rice moisture sensor I. INTRODUCTION Currently, moisture content sensors that use electromagnetic-based technique (EM) have been continually studied and researched for various kinds of applications. With the EM wave property, the designated RF/microwave sensors can rapidly investigate the moisture content of material under test (MUT). Then, the obtained moisture contents will be further translated into other useful parameters. For examples of agricultural applications, the detection of moisture content in production process of rice and Hevea rubber can make the advantages of monitoring and controlling the product qualities. In [1], Mujumdar’s research practically shows the development of modern measurement system for moisture content. The system is applied for drying industry to manage the moisture and quality of a product. Many types of sensor solution have been discussed and considered in the process of drying. Then, to manage the water in a plant, Kirkham has improved the measurement of sensor system for moisture content in the soil. The sensor can predict and identify the property and type of soil by calculating the portion of water in plant [2]. In particular of construction work, brick is the main component which has been employed in the ancient archaeological site of Thailand. Wattanachai has reported the relationship between the moisture content and deterioration of brick. This can be the assistance to predict the lifetime of construction [3]. Then, the detected variation of moisture content in the high ancient church is proposed by Ferrettti in [4]. The experiment shows that the moisture content can be observed via the wall of church. It results in the collapse prediction of 800 years in advance. Apparently, most of them are related to the variation of water portion which is the main effect for the moisture content in the MUT. By using the EM technique, the portion can be related and transformed to permittivity value. Thus, the change of water portion in the MUT can also change the permittivity value [5]-[7]. To perform the permittivity measurement systems, various systems by using microwave sensor are proposed in [8]. Generally, the permittivity measurement systems are grouped into two techniques including resonance and non- resonance systems as found in [9]-[11]. In such systems, the measurement technology operates via the numerical process of scattering parameters. The microwave sensor systems using a single and multiple port sensing devices are developed in [12]-[14]. In [12], microwave moisture content sensors using microstrip ring and coupled line resonator structures are developed for sensing the moisture contents of rice. From this research, it can be seen that the coupled line can provide the wider operating frequency of measurement, while the ring resonator gives lower error because of its higher quality factor. Then, the capacitive type microwave sensor is reported in [13]. This proposed sensor consists of two cylindrical metal elements which are overlapped with each other resulting in a capacitive values. The moisture content variation in material can affect to the small change of capacitance resulting in performance improvement. For the low profile and cheap system of permittivity measurement in the industry section, the quarter-wave length microstrip resonator must be used. The sensing area of this sensor is located in bottom side with the slotted ground plane. The permittivity data are converted from the shift of resonance frequency and the obtained bandwidth adjustment when the material is tested [14]. Subsequently, this approach is further adapted for the on-site measurement system of rice grain and latex rubber which are presented in [15]. Recently, the metamaterial-based resonator structure has been employed to built up a microwave sensor. This work results in small size of sensor and higher performance. One example of soil moisture content sensor using metamaterial- based resonator is shown in [16]. The sensor structure is split ring resonator (SRR) that can provide the wide range of sensing frequency. Then, many researchers have reported the sensors that employ SRR and composite right/left-handed transmission line (CRLH-TL) structures in the systems [17], [18]. As seen, several researches work on the EM-based sensor system in order to increase sensing performances. However, most of them propose the sensor structures based on microwave circuits including transmission lines and resonators. With these sensor structures, the MUT must be placed near to the sensors, so they will not be suitable for some