How to Test a 4-20mA Transmitter Using FNIRSI SG-004A Malaysia
How to Test a 4-20mA Transmitter Using FNIRSI SG-004A Malaysia 4-20mA transmitters are commonly used in factories, process plants and industrial automation systems to transmit pressure, temperature, flow and level measurements to PLC and DCS controllers. When a transmitter produces an incorrect reading, technicians must determine whether the problem comes from the transmitter, signal wiring, power supply or PLC analog input. The FNIRSI SG-004A Multifunction Signal Generator supports current signal measurement and simulation, making it useful for industrial maintenance and troubleshooting. Why Test a 4-20mA Transmitter? A 4-20mA transmitter converts a physical measurement into an electrical current signal. For example, a pressure transmitter with a 010 bar range may produce: Output CurrentPressure Reading4mA0 bar8mA2.5 bar12mA5 bar16mA7.5 bar20mA10 bar If the transmitter output does not match the expected pressure, further troubleshooting is required. Method 1: Check the Transmitter Output The SG-004A can help technicians measure the transmitter's current output. Step 1: Identify the transmitter wiring configuration. Step 2: Verify the power supply and signal connections. Step 3: Select the appropriate current measurement mode. Step 4: Connect the SG-004A according to its operating instructions. Step 5: Compare the measured current with the expected process value. For current measurement, use the correct series connection. Never connect a current measurement input directly across a power supply. Method 2: Simulate a 420mA Signal If the transmitter is suspected to be faulty, technicians can test the PLC analog input using a simulated current signal. Step 1: Confirm that the PLC input supports 4-20mA. Step 2: Identify the required active or passive current mode. Step 3: Safely isolate the original transmitter. Step 4: Connect the SG-004A using the correct wiring configuration. Step 5: Generate 4mA, 12mA and 20mA signals. Step 6: Check whether the PLC displays the expected values. If the PLC responds correctly, technicians can investigate the transmitter and field wiring. If the PLC displays incorrect values, check the analog input module, signal scaling and PLC configuration. Common 4-20mA Signal Problems ProblemPossible CauseNo signalOpen circuit or missing powerUnstable readingLoose wiring or electrical interferenceIncorrect readingWrong scaling or transmitter faultPLC reading does not changeAnalog input or configuration issue FNIRSI SG-004A Industrial Applications The SG-004A is useful for: PLC analog input testing 4-20mA transmitter troubleshooting Pressure and temperature signal simulation Control panel commissioning Industrial automation maintenance Process instrumentation testing It provides a practical solution for technicians who need to generate or measure electrical signals during maintenance work. Who Should Use the SG-004A? The FNIRSI SG-004A is suitable for instrumentation technicians, factory maintenance engineers, PLC programmers, automation contractors and technical training centres. It is intended for functional testing and troubleshooting. Applications requiring traceable calibration should use suitably calibrated reference instruments. FNIRSI SG-004A Signal Generator Malaysia MTM Precision Sdn Bhd supplies industrial testing and measuring instruments for Malaysian factories, maintenance contractors and engineering companies. For enquiries about the FNIRSI SG-004A, customers may WhatsApp us a photo of their transmitter, PLC module or existing testing equipment. MTM Precision Sdn Bhd Showroom & Service Centre No. 29-1 & 2, Jalan Bandar 18, Pusat Bandar Puchong, 47160 Puchong, Selangor, Malaysia. Tel: 03-8080 7172 WhatsApp: +6016-660 7346 Email: mtmpre@yahoo.com Website: www.mtmpre.com.my We serve customers across Kuala Lumpur, Selangor, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kedah, Kelantan, Terengganu, Perlis, Sabah and Sarawak.
08 Oct 2026
