PENGEMBANGAN RANCANG BANGUN RESISTIVITY METER DIGITAL DENGAN SISTEM PENAMPIL DAN PENYIMPAN DATA BERBASIS INTERNET OF THINGS

Fitri Puspasari, Prof. Dr. Sismanto, M.Si.

2023 | Disertasi | S3 Ilmu Fisika

Survei geolistrik resistivitas bertujuan untuk mengetahui sifat aliran listrik pada suatu formasi batuan didalam bumi dari sisi nilai resistivitasnya. Biaya beli atau sewa instrumen geolistrik komersial yaitu resistivity meter cukup mahal, belum termasuk biaya operator, pakar interpretasi data, serta biaya software komersial. Beberapa peneliti telah mengkaji dan melakukan pembuatan rancang bangun resistivity meter baik jenis analog maupun digital. Umumnya proses pencatatan dan plotting data dilakukan secara manual melalui tabel dan grafik, sehingga kurang efisien waktu serta bisa terjadi kesalahan pembacaan maupun penulisan oleh operator. Saat ini, teknologi penyimpanan dan pemantauan data secara real time dan jarak jauh telah berkembang untuk memudahkan operator dalam akuisisi data yaitu pemanfaatan mikrokontroller. Tujuan dari disertasi ini adalah pengaplikasian sistem Internet of Things (IoT) berbasis mikrokontroler NodeMCU ESP8266 dengan memanfaatkan platform ThingSpeak untuk menunjang proses monitoring, pengiriman dan penyimpanan data pada rancang bangun resistivity meter. Metode dalam penelitian ini ialah merancang sistem hardware dan software rancang bangun resistivity meter dan melakukan beberapa pengujian diantaranya pengujian karakterisasi sensor, kalibrasi prototipe uji, pengujian stabilitas data dan pengujian transmisi data. Metode kalibrasi dilakukan dengan instrumen standar untuk keperluan uji validasi data. Prinsip akuisisi data metode survei geolistrik resistivitas ialah dengan menginjeksikan arus pada beban melalui dua elektroda arus dan membaca nilai potensialnya melalui dua elektroda potensialnya. Hasil dari penelitian ini adalah, arus injeksi yang berhasil diimplementasikan ialah 12, 18, 62, 83, 125, dan 250 mA. Pada hasil kalibrasi, pengukuran resistansi dapat terukur dengan baik pada pengukuran resistansi 10 hingga 4000 ? dengan rata-rata ketidakpastian relatif sebesar 5,56 ?n rata-rata standar deviasi 2,03. Pada uji coba pengukuran resistansi di lapangan dengan prototipe resistivity meter didapatkan data resistansi berkisar 0,2 hingga 19,3 ?, dengan simpangan diatas 5% mulai terjadi pada pembacaan resistansi dibawah 10 ?. Adanya simpangan pada pengukuran dapat terjadi karena penurunan kemampuan ukur yaitu sumber tegangan hanya 42 Volt serta dapat dipengaruhi oleh kondisi lingkungan yaitu kondisi tanah yang kering, serta kesalahan penempatan jarak elektroda. Data hasil pengukuran oleh prototipe resistivity meter dapat disimpan di microSD dan dikirim ke ThingSpeak.com dalam bentuk grafik dan file .csv dengan delay pengukuran sebesar 10 detik. Berdasarkan hasil pengujian, kestabilan pembacaan data harus memperhatikan kenaikan suhu pada lingkungn dilapangan. Kenaikan suhu diatas 35°C menyebabkan ketidakstabilan pembacaan data.

The geoelectric resistivity survey aims to determine the nature of the electric flow in a rock formation in the earth in terms of its resistivity value. The cost of purchasing or renting a commercial geoelectric instrument, namely a resistivity meter, is quite expensive, not including the costs of operators, data interpretation experts, and commercial software costs. Several researchers have studied and carried out designs for resistivity meters, both analog and digital. Generally, the process of recording and plotting data is manually through tables and graphs, so it is less time efficient and reading errors can occur by operators. Currently, the use of microcontrollers as a technology for storing and monitoring data in real time and remotely has been developed to make it easier for operators to acquire data. The aim of this dissertation is the application of an Internet of Things (IoT) system based on the NodeMCU ESP8266 microcontroller by utilizing the ThingSpeak platform to support the process of monitoring, sending and storing data in resistivity meter design. The method in this research is to design a resistivity meter hardware and software system and carry out several tests including sensor characterization testing, test prototype calibration, data stability testing and data transmission testing. The calibration method is carried out with standard instruments for data validation testing purposes. The principle of data acquisition for the resistivity geoelectric survey method is to inject current into the load through two current electrodes and read the potential value through the two potential electrodes. The results of this research are that the injection currents that were successfully implemented were 12, 18, 62, 83, 125, and 250 mA. In the calibration results, resistance measurements can be measured well in resistance measurements from 10 to 4000 ? with an average relative uncertainty of 5.56% and an average standard deviation of 2.03. In trials measuring resistance in the field with a prototype resistivity meter, resistance data was obtained ranging from 0.2 to 19.3 ?, with deviations above 5% starting to occur at resistance readings below 10 ?. Deviations in measurements can occur due to a decrease in measuring capability, namely the voltage source is only 42 Volts and can be influenced by environmental conditions, namely dry soil conditions, as well as errors in electrode distance placement. Data from measurements by the resistivity meter prototype can be stored on a microSD and sent to ThingSpeak.com in the form of graphs and .csv files with a measurement delay of 10 seconds. Based on the test results, the stability of data reading must take into account the increase in temperature in the field environment. An increase in temperature above 35°C causes data reading instability.

Kata Kunci : Geoelectric, Resistivity, Resistivity meter, Internet of Things