Typical Test Items for Automotive Product Electronic and Electrical Testing and Their Specific Analyses

Electromagnetic Compatibility Testing (EMC)

• Radiated Emission Testing
  • Purpose: To detect whether the electromagnetic radiation emitted by automotive electronic and electrical equipment into the surrounding space during normal operation exceeds the standard. This is because excessive electromagnetic radiation may interfere with other vehicle electronic equipment or even electronic devices outside the vehicle, such as nearby communication equipment and medical equipment.
  • Testing Method: The Equipment Under Test (EUT) is placed in an anechoic chamber. Antennas are used to receive the electromagnetic radiation signals emitted by the EUT during operation. Then, a spectrum analyzer is employed to analyze the signals, determine their radiation intensities at different frequencies, and compare them with the corresponding standard limits. For example, for automotive components, the international standard CISPR 25 stipulates the radiated emission limits in different frequency bands.
• Conducted Emission Testing
  • Purpose: To evaluate the level of electromagnetic interference conducted by automotive electronic equipment to other equipment through power lines, signal lines and other conductors. The electrical systems inside a vehicle are interconnected by wire harnesses. If the conducted interference is too large, it will affect the normal operation of other equipment on the same wire harness.
  • Testing Method: An Artificial Power Network (LISN) is used to connect the EUT to the power grid. The function of the LISN is to isolate the interference in the power grid, provide a stable power impedance, and measure the interference current or voltage conducted by the EUT to the power lines at the same time. The measured signals are also analyzed by a spectrum analyzer and compared with the conducted emission limits specified in the standards.
• Radiated Immunity Testing
  • Purpose: To determine the tolerance ability of automotive electronic and electrical systems when subjected to external electromagnetic radiation interference. In the actual usage environment, vehicles may be affected by electromagnetic radiation from various external sources such as radio stations, mobile communication base stations and radars. It is necessary to ensure that the in-vehicle electronic equipment can work normally under such interferences.
  • Testing Method: In an anechoic chamber, antennas are used to emit electromagnetic interference signals with specified intensities and frequency ranges to the EUT. Meanwhile, the working state of the EUT is monitored to observe whether there are functional abnormalities, performance degradation or data errors. For example, when conducting radiated immunity testing on an automotive Electronic Control Unit (ECU), the field strength of the interference signals may be set within the range of 10 – 100 V/m according to different standards and application scenarios.
• Conducted Immunity Testing
  • Purpose: To test the resistance ability of automotive electronic equipment to interference signals entering through conduction paths such as power lines and signal lines. For example, when the vehicle starts, the instant voltage fluctuations generated on the power lines due to the start-up of high-power equipment such as motors may be conducted to other electronic equipment. It is necessary to test the immunity performance of the equipment against such interferences.
  • Testing Method: A signal generator is used to inject specified interference signals, such as fast transient bursts and surges, into the power ports and signal ports of the EUT. Meanwhile, the response of the EUT is observed. Taking the fast transient burst test as an example, a series of pulse signals with relatively high amplitudes (such as ±2 kV) and high repetition frequencies (such as 5 kHz) are injected into the power lines of the EUT to check whether the equipment can work normally.

Electrical Performance Testing

• Voltage Testing
  • Purpose: To ensure that automotive electronic equipment can work normally within the specified power voltage range. The voltage of the vehicle power supply system will fluctuate due to factors such as battery status, generator output and load changes. The equipment needs to adapt to these voltage changes.
  • Testing Method: An adjustable power supply is used to power the EUT to simulate the voltages of the vehicle power supply system under different working conditions. For example, the low voltage during startup (usually around 9 – 10 V), the nominal voltage during normal operation (12 V or 24 V system), and the high voltage during charging (which may reach 14 – 15 V or 28 – 30 V). Meanwhile, it is checked whether the functions and performance indicators of the EUT meet the requirements.
• Current Testing
  • Purpose: To measure the current magnitude when automotive electronic equipment is working. On the one hand, it can determine the power consumption of the equipment. On the other hand, it can check whether there are abnormal conditions such as overcurrent. Excessive current may lead to problems such as overheating of lines and blowing of fuses.
  • Testing Method: An ammeter is connected in series in the power supply circuit of the EUT to measure the current under normal working conditions and different load conditions of the equipment. For example, for the vehicle lighting system, by measuring the currents when different lamps (such as headlights, turn signals, brake lights, etc.) are working, it can be judged whether the lamps are working normally and whether there are short circuits or overloads in the lines.
• Insulation Resistance Testing
  • Purpose: To evaluate the insulation performance of automotive electronic equipment and prevent potential safety hazards such as electric leakage and short circuits caused by poor insulation. Especially for high-voltage systems (such as the power battery system of electric vehicles), good insulation resistance is the key to ensuring personal safety and the normal operation of the equipment.
  • Testing Method: An insulation resistance tester is used to apply a specified direct current voltage (such as 500 V or 1000 V) between the live parts and the shell of the EUT or between circuits with different insulation levels, and measure the insulation resistance value. Generally, the insulation resistance is required to be greater than the specified minimum value. For example, for the high-voltage system of electric vehicles, the insulation resistance is usually required to be no less than 100 Ω/V.
• Ground Continuity Testing
  • Purpose: To check whether the grounding of automotive electronic equipment is good, ensure that current can be safely introduced into the earth in case of equipment failure, and also reduce electromagnetic interference.
  • Testing Method: The ground continuity is evaluated by measuring the resistance of the grounding path. A low-resistance tester is used to measure the resistance between the grounding terminal of the equipment and the vehicle grounding electrode. The grounding resistance value is required to be less than the specified limit, generally ranging from a few milliohms to dozens of milliohms.

Environmental Adaptability Testing

• Temperature Testing
  • Purpose: To verify the performance and reliability of automotive electronic and electrical equipment in different temperature environments. Vehicles are used in different regions and seasons, and electronic equipment needs to withstand temperature changes from extremely cold to extremely hot.
  • Testing Method: It includes high-temperature testing and low-temperature testing. During high-temperature testing, the EUT is placed in a high-temperature test chamber, and the temperature range (such as 85 °C – 105 °C) and test time (such as 24 – 48 hours) are set. It is observed whether there are performance degradations, material deformations, component damages and other situations in the equipment under the high-temperature environment. The low-temperature testing is similar. The temperature of the test chamber is set in the low-temperature range (such as – 40 °C – - 30 °C), and the function state of the equipment during low-temperature startup, operation and storage is checked.
• Humidity Testing
  • Purpose: To evaluate the performance and moisture-proof ability of automotive electronic equipment in a humid environment. The interior of a vehicle may have a high-humidity environment due to factors such as the breathing of passengers and rain leakage. Electronic equipment needs to be able to resist the influence of humidity.
  • Testing Method: Constant humidity testing and alternating humidity testing are adopted. In the constant humidity testing, the EUT is placed in a test chamber with a humidity of 90% – 95% and a temperature of 40 °C – 60 °C for a certain period of time (such as 48 – 96 hours). It is checked whether there are problems such as moisture damage, short circuits and corrosion in the equipment. The alternating humidity testing simulates an environment where humidity and temperature change periodically, which is closer to the actual usage situation, and the durability of the equipment in such a complex environment is observed.
• Vibration Testing
  • Purpose: To simulate the impact of vibrations on electronic and electrical equipment during vehicle driving and ensure the reliability of the mechanical structure and electrical connections of the equipment in a vibration environment. During vehicle driving, the operation of the engine and the bumps on the road will generate vibrations.
  • Testing Method: A vibration test bench is used. The vibration parameters are set according to the actual vibration spectrum and amplitude of the vehicle. For example, according to different vehicle types and road conditions, the frequency range (such as 10 Hz – 2000 Hz) and acceleration amplitude (such as 1 g – 10 g) are set. The EUT is subjected to vibration tests in different directions (such as X, Y, Z axes). The duration may range from several hours to dozens of hours. During the testing process, it is checked whether there are problems such as component loosening, solder joint detachment and changes in electrical performance in the equipment.
• Salt Spray Testing
  • Purpose: For vehicles used in coastal areas or on roads where snow-melting salt is used, this test is to detect the corrosion resistance ability of electronic and electrical equipment. Chloride ions in the salt spray will have a corrosive effect on metal parts, affecting the service life and performance of the equipment.
  • Testing Method: The EUT is placed in a salt spray test chamber filled with a certain concentration of salt spray (such as 5% sodium chloride solution). The spray time (such as 24 – 72 hours) and temperature (such as 35 °C) are set. It is observed whether there are phenomena such as corrosion and rust on the metal parts (such as the shell, connectors, etc.) on the surface of the equipment, and at the same time, it is checked whether the function of the equipment is affected.