{"id":63608,"date":"2024-12-10T08:35:17","date_gmt":"2024-12-10T13:35:17","guid":{"rendered":"https:\/\/www.engineersgarage.com\/?p=63608"},"modified":"2024-12-11T09:19:27","modified_gmt":"2024-12-11T14:19:27","slug":"non-invasive-current-sensor-with-arduino","status":"publish","type":"post","link":"https:\/\/www.engineersgarage.com\/non-invasive-current-sensor-with-arduino\/","title":{"rendered":"Non-invasive current sensor with Arduino"},"content":{"rendered":"

The idea of noninvasive current measurement is not new. Commercial devices are available which can measure current without any physical contact. However, the topic was not popular among the DIY community because of the complexity and nonexistence of the compact non-invasive sensors, which could be studied at low power. Luckily, we have small and reliable current transformers that can be used to measure alternating current without physical contact.<\/p>\n

Current transformers (CT) have the same physical parts as a regular transformer. They are split-core means primary and secondary coils can be separated. They differ from regular transformers on working principle. The primary coil induces a current in the secondary, proportional to current passing intensity through the primary (Electromagnetic induction).<\/p>\n

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A CT sensor is shown above. Split cores can be seen with a permanent magnet. We open the cores and place a live current-carrying wire in between and then close the cores. Note that we only place anode or cathode in between the cores. Inserting both the wires at once will yield no or misleading results. Why?<\/p>\n

Current flows from anode to cathode. If we place both the wires simultaneously in the core, then the anode will cancel the cathode electrical field due to opposite polarity. Hence one wire is needed to measure the current. Recall when measuring current physically with a digital multimeter (DMM), we cut the wire and place the DMM probes in series. Same we did in the CT case, just the physical contact is not made.<\/p>\n

Current transformers output current or voltage, which is directly proportional to the input current. Output current is an RMS (root mean square), and voltage is in AC form. We need to convert both the quantities in DC to measure them using Arduino or any other microcontroller.<\/p>\n

Let\u2019s begin<\/strong><\/p>\n

I decided to use Arduino and a predefined library named \u201cEmon\u201d energy monitor to measure the current flowing through a live wire. To make CT output compatible with Arduino, we must transform it into digital form. We have few options here.<\/p>\n