2.6.1 Laboratory Reference Conditions
In order to minimize the impact of environmental parameters on test results, the tests shall be carried out in climatic and electromagnetic reference conditions as specified in 2.6.1.1 and 2.6.1.2.
2.6.1.1. Climatic Conditions
In the case of air discharge testing, the climatic conditions shall be within the following ranges:
- ambient temperature: 15 ˚C to 35 ˚C;
- relative humidity: 30 % to 60 %;
- atmospheric pressure: 86 kPa (860 mbar) to 106 kPa (1,060 mbar).
NOTE Any other values are specified in the product specification.
The EUT shall be operated within its intended climatic conditions.
2.6.1.2. Electromagnetic Conditions
The electromagnetic environment of the laboratory shall not influence the test results.
2.6.2 EUT Exercising
The test programs and software shall be chosen so as to exercise all normal modes of operation of the EUT. The use of special exercising software is encouraged, but permitted only where it ca be shown that the EUT is being comprehensively exercised.
For conformance testing, the EUT shall be continually operated in its most sensitive mode (program cycle) which shall be determined by preliminary testing.
If monitoring equipment is required, it should be decoupled in order to reduce the possibility of erroneous failure indication.
2.6.3 Execution of the Test
The testing shall be performed by direct and indirect application of discharges to the EUT according to a test plan. This should include:
- representative operating conditions of the EUT;
- whether the EUT should be tested as table-top or floor-standing;
- the points at which discharges are to be applied;
- at each point, whether contact or air discharges are to be applied;
- the test level to be applied;
- the number of discharges to be applied at each point for compliance testing;
- whether post-installation tests are also to be applied.
It may be necessary to carry out some investigatory testing to establish some aspects of the test plan.
2.6.4 Direct Application of Discharges to the EUT
Unless stated otherwise in the generic, product-related or product-family standards, the static electricity discharges shall be applied only to those points and surfaces of the EUT which are accessible to persons during normal use. The following exclusions apply (i.e.
discharges are not applied to those items):
(a) those points and surfaces which are only accessible under maintenance. In this case, special ESD mitigation procedures shall be given in the accompanying documentation;
(b) those points and surfaces which are only accessible under service by the (end-)user. Examples of these rarely accessed points are as follows: battery contacts while changing batteries, a cassette in a telephone answering machine, etc.;
(c) those points and surfaces of equipment which are no longer accessible after fixed installation or after following the instructions for use, for example, the bottom and/or wallside of equipment or areas behind fitted connectors;
(d) the contacts of coaxial and multi-pin connectors which are provided with a
metallic connector shell. In this case, contact discharges shall only be applied to the metallic shell of that connector.
Contacts within a non-conductive (for example, plastic) connector and which are accessible shall be tested by the air-discharges test only. This est shall be carried out by using the rounded tip finger on the ESD generator.
In general, six cases shall be considered in table 2.4.
(e) those contacts of connectors or other accessible parts that are ESD sensitive because of functional reasons and are provided with an ESD warning label, for example, r.f. inputs from measurement, receiving or other communication functions.
Rationale: Many connector ports are designed to handle high-frequency information, either analogue or digital, and there fore cannot be provided with sufficient overvoltage protection devices. In the case of analogue signals, bandpass filters may be a solution. Overvoltage protecting diodes have too much stray capacitance to be useful at the frequencies at which the EUT is designed to operate.
In all previous cases, special ESD mitigation procedures are recommended, to be given in the accompanying documentation. The test voltage shall be increased from the minimum to the selected test level, in order to determine any threshold of failure. The final test level should not exceed the product specification value in order to avoid damage to the equipment.
The test shall be performed with single discharges. On preselected points at least ten single discharges (in the most sensitive polarity) shall be applied. For the time interval between successive single discharges an initial value of 1 s is recommended. Longer intervals may be necessary to determine whether a system failure has occurred.
NOTE The points to which the discharges should be applied may be selected by means of an exploration carried out at a repetition rate of 20 discharges per second, or more.
The ESD generator shall be held perpendicular to the surface to which the discharge is applied. This improves repeatability of the test results. The discharge return cable of the generator shall be kept at a distance of at least 0.2 m from the EUT whilst the discharge is being applied. In the case of contact discharges, the tip of the discharge electrode shall touch the EUT, before the discharge switch is operated. In the case of painted surfaces covering a conducting substrate, the following procedure shall be adopted:
If the coating is not declared to be an insulating coating by the equipment manufacturer, then the pointed tip of the generator shall penetrate the coating so as to make contact with the conducting substrate. Coating declared as insulating by the manufacturer shall only be submitted to the air discharge. The contact discharge test shall not be applied to such surfaces.
In the case of air discharges, the round discharge tip of the discharge electrode shall be approached as fast as possible (without causing mechanical damage) to touch the EUT.
After each discharge, the ESD generator (discharge electrode) shall be removed from the EUT. The generator is then retriggered for a new single discharge. This procedure shall be repeated until the discharges are completed. In the case of an air discharge test, the discharge switch, which is used for contact discharge, shall be closed.
2.6.5 Indirect Application of the Discharge
Discharges to objects placed or installed near the EUT shall be simulated by applying the discharges of the ESD generator to a coupling plane, in the contact discharge mode.
In addition to the test procedure described in 2.6.5, the requirements given in 2.6.5.1 and 2.6.5.2 shall be met.
2.6.5.1. Horizontal Coupling Plane (HCP) under the EUT
Discharge to the HCP shall be made horizontally to the edge of the HCP.
At least 10 single discharges (in the most sensitive polarity) shall be applied at the front edge of each HCP opposite the centre point of each unit (if applicable) of the EUT and 0.1 m from the front of the EUT. The long axis of the discharge electrode shall be in the plane of the HCP and perpendicular to its front edge during the discharge.
The discharge electrode shall be in contact with the edge of the HCP .
In addition, consideration should be given to exposing all sides of the EUT to this test.
2.6.5.2. Vertical Coupling Plane
At least 10 single discharges (in the most sensitive polarity) shall be applied to the centre of one vertical edge of the coupling plane. The coupling p lane, of dimensions 0.5 m x 0.5 m, is placed parallel to, and positioned at a distance of 0.1 m from, the EUT.
Discharges shall be applied to the coupling plane, with sufficient different positions such that the four faces of the EUT are completely illuminated.