The immunity of conducting disturbance is an important test to measure the EMC index of the equipment under test (EUT). At present, the test of this project in China is mainly based on the GB/T17626.6:2008 standard, which is about the resistance of the equipment to the conduct disturbance from the 9KHz~80MHz frequency range. The equipment is coupled with RF by at least one cable (such as power line, signal line, ground line etc.), and the actual test frequency is usually 150 KHz ~ (80) MHz. Its test configuration diagram is as the following:
Conduct Disturbance Immunity Test Configuration Diagram
1. The purpose and application of conducting disturbance immunity test.
The main source of disturbance involved in the GB/T17626.6:2008 standard is the electromagnetic field generated by the RF transmitter in the 9kHz~80MHz frequency range. The electromagnetic field acts on the wiring lines, communication lines and interface cables of electrical and electronic equipment, which may be as long as several wavelengths of the interference frequency, so the leads become passive antennas. By receiving the induction of the external electromagnetic field, the lead cable can coupling the external interference to the device by conducting mode (eventually, disturb the device in the form of near field electromagnetic formed by the RF voltage and current), finally affect the normal operation of the equipment. Therefore, the purpose of this standard is to establish a public reference for evaluating the resistance to conduct disturbance of RF field induction, and to provide a basic reference for the professional technical committee or the users and manufacturers of the products concerned.
2. Conduct disturbance immunity test arrangement and test
1) Typical test arrangement is as follows:
a. Where coupling and decoupling devices are required, the distance between them and the equipment to be tested should be between 0.1 and 0.3m, and be connected to the reference connection floor. Connection cables between coupling and decoupling devices and the equipment to be tested shall be as short as possible and shall not be tied or coiled.
b. Other grounding terminals of the tested equipment should also be connected to the reference floor by coupling and decoupling network CDN-M1.
c. For all tests, the total length of cable between the tested equipment and the auxiliary equipment (including any internal cable of the coupled decoupling network used) shall not exceed the maximum length specified by the manufacturer of the equipment under test.
d. If the device under test has a keyboard or portable attachment, the simulated hand should be placed on the keyboard or wound around the attachment and connected to the reference connection floor.
2) Test Procedure
a. The equipment to be tested shall be tested under expected operating and climatic conditions. Record the ambient temperature and relative humidity at the time of the test.
b. The calibration of the test system should be carried out before each test to avoid test error and ensure that the system meets the necessary common mode impedance.
c. The test signal generator is connected to the coupling device (coupling and decoupling network, electromagnetic clamp, current injection probe) in turn.
d. Grade of test level is set according to requirement, the range of sweep frequency is from 150kHz to 80MHz or 230MHz, 1kHz sine wave is used to modulate the amplitude and the modulation rate is 80% to the level of modulated interference signal. When sweep with frequency increasing progressively, the step size should not exceed 1% of the previous frequency. At each frequency, the resident time of the amplitude modulated carrier shall be no less than the necessary time for the operation and response of the device to be tested, but the minimum shall not be less than 0.5s. Sensitive frequencies (e.g. clock frequencies) should be analyzed separately.
3) Evaluation of test results
The test results shall be classified according to the loss of function or deterioration of the performance of the tested equipment, it is related with the performance level specified by the manufacturer and the demand-side of the test, or by the agreement of the manufacturer and the buyer of the product. The recommended categories are as follows:
a. Normal performance in the limits imposed by the manufacturer, the demand side or the buyer.
b. Temporary performance degradation and loss of function after termination of interference, and no artificial intervention until the device under test resumes its normal performance.
c. Temporary performance degradation and loss of function, recovery requires human intervention.
d. Failure of hardware or software, or loss of data, resulting in unrecoverable degradation of performance and loss of functionality.