Design and Development of Portable EMI/EMC Measurement Instrument

Shruti Dhongade *1, Manali Patil *2, Sayali Shingade *3, Pranjali Paikekar *4, Prof .E. C. Patil *5
*1,2,3,4 BTECH Students, Department Of Electronics And Telecommunication Engineering, KIT’S College of Engineering, Kolhapur, Maharashtra, India

*5Assistant Professor, Department Of Electronics And Telecommunication Engineering, KIT’S College of Engineering, Kolhapur, Maharashtra, India

Abstract:In modern electronic systems, high frequency circuits and wireless devices are widely used, which makes Electromagnetic Interference (EMI) a serious challenge for them. Commercial EMI measuring instruments like spectrum analyzer and EMI receiver are accurate but are expensive, bulky and not available for academic and small scale industrial use. This paper describes the design and development of a low-cost, portable EMI/EMC measurement instrument as a practical alternative. Electromagnetic emissions are captured using a near-field magnetic probe (9 kHz3 GHz). These are amplified by a wideband RF low-noise amplifier (0.1 MHz-2 GHz, ~30 dB gain). A Schottky diode detector circuit is formed by a BAT43 diode, 100 pF filter capacitor, 47 kΩ load resistor, and 470 nH RF choke. This circuit converts the amplified RF signal to a stable DC voltage proportional to the EMI signal strength. The PIC16F877A microcontroller digitizes this DC voltage with its 10-bit ADC, processes the signal and displays real-time EMI levels on a 16×2 alphanumeric LCD. The system uses RC filtering and op-amp buffering to enable stable, repeatable measurements under a variety of electromagnetic conditions. Experimental results show that EMI can reliably detect switching power supplies, microcontroller boards and RF modules, with LCD readings that vary dynamically with the change of the intensity of the interference and the distance of the probe from the source. The proposed system is compact, battery operated and low cost and thus well suited for PCB debugging, educational demonstrations and basic pre-compliance EMC screening.

Keywords: EMI, EMC, Near-Field Probe, RF Amplifier, Schottky Diode, PIC16F877A, ADC, Envelope Detector, LCD Display, Portable Measurement Instrument