ANSI ESD-S4.2 2006 pdf download For the Protection of Electrostatic Discharge Susceptible Items ESD Protective Worksurfaces Charge Dissipation Characteristics
4.1.3 Disk Raising/Lowering Mechanism (RLM) The test apparatus shall contain a mechanism used to lower and raise the disk assembly to and from the tested worksurface. Any process may be used to accomplish this task (ie. hydraulic, pneumatic, etc.) as long as the raising/lowering speed is controllable and provides uniform stroke movement and stability to the suspended disk assembly. The RLM must also be capable of suspending the disk assembly above the tested work surface while being electrically isolated from it. The RLM must be controlled such that a specified contact time between the disk assembly and the tested worksurface is maintained.
4.1.4 Control Pane/ and Contact Timer A control panel and contact timer shall be used to activate the RLM and control the time in which the disk assembly is in contact with the test sample. Contact time shall be specified in the test procedure.
4.1.5 Test Cabling The specified test voltage is applied to the disk assembly from a charge plate monitor through test cabling. The test cabling also provides the electrical connection between the disk assembly and the charge plate monitor when monitoring the resultant disk assembly voltage after it is raised from the sample. The entire cable length shall be no greater than 121.92 cm (4 feet) in length and consist of two bonded portions. The first portion shall consist of 1 meter of insulated high voltage wire (40KV minimum). It shall be electrically bonded to a smaller 30 cm (11.7 inches) section of insulated (28 gauge or greater) wire. The high voltage wire end of the cable is connected to the isolated plate of the charge plate monitor and the smaller wire end is connected to the disk assembly. The cable shall not contact any portion of the test apparatus between the disk assembly and the charge plate monitor. This can be accomplished through an electrically insulative standoff material clamped to the test apparatus housing. The use of this isolation technique as well as the specified wire types ensures electrical isolation of the disk assembly. Test cable acceptability is verified through the Disk lsolation/System Verification Test outlined herein.
4.1.6 Disk Suspension Cord The disk assembly shall be suspended and electrically isolated from the RLM. Braided nyion lacing tape/ Cord IAW MIL-T-43435, Type I, Size 5, Finish B or equivalent is recommended.
4.1.7 Apparatus Housing It is recommended that the suspended disk assembly, test sample support table and test sample be contained within a grounded conductive housing. The housing provides some limited shielding from extemal noise or EMI sources and a ground point for the worksurface test samples. Its size is dependent on overall system design but must accomnhodate all test apparatus components, as a minimum, the disk assembly, test sample support table and test sample.