Conformity Magazine - October 2008 - (Page 18)

ESD Open Forum Voltage Levels for Higher Capacitance Verification Provided by the ESD Association Q: A: Why doesn’t the ANSI/ESDA CDM-5.3.1 document provide current values for the higher capacitance verification module (30pF) for the 3.0GHz and 1.0 GHz BW measurements? The tables in the standard do not provide these data or give guidance as to what the data should be. Should we expect any linearity? You are correct, the standard does not provide any values at all for voltage levels for the higher capacitance module, and the reasons are many. However, data does exist, but it was collected at one test lab only. The plan of the standard’s Working Group is to collect fresh data, using several test labs including both manufacturers and users of the CDM tester. The good news is that like the small capacitance (4pF) data (see Table 1 for 3.0 GHz BW measurements), the current values for the larger module are linear from 125V to 2000 V. This Round Robin data will then be analyzed and used in the next revision of the document. For the 1.0 GHz BW measurement, data also exists for the 30 pF module, and as is the case for the 3.0GHz data, only one data point is available. However, a graph (not included here) of current versus voltage (x-axis) is linear from 125 V to 2000V. This 1 GHz BW data was collected using a splitter to take the current from the CDM tester to 2 scopes; one was a 3.0GHz BW scope, and the 2nd, a 1.0GHz BW scope. Hence, both scopes saw the same CDM event each time a data set was collected. This correlates well with the linearity shown in Table 2 for the smaller module. The linearity is to be expected even though there is a natural variance in each air arc discharge. The waveform verification nodules used to collect the current data are made up of gold-plated or nickel-plated etched copper disks on single sided insulative circuit board material. The circuit board material can be FR-4 or RF-35. Each disk is etched in the center of a square of the insulative material. The capacitance is always measured with the non-metalized non-disc side of the verification modules in intimate contact with the metal surface of the grounded field charging plate in the CDM tester. We have found the RF-35 material, which is made up 4 pF Verification module Amperes ± 20% 1.9 3.75 7.5 15.0 22.5 30.00 18.00 30 pF Verification module Amperes ± 20% Charge voltage Volts ± 5% 125 250 500 1000 1500 2000 Symbol Ip1 Ip1 Ip1 Ip1 Ip1 Ip1 Table 1: Requirements for the 3.0 gigahertz BW measurement 18 Conformity oCtober 2008

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Conformity Magazine - October 2008 Contents Editor's Note FCC Releases Annual Report on National Do-Not-Call Registry Commission Cracks Down (for the Fourth Time!) On Junk Fax Marketer FCC Releases Quarterly Reports on Consumer Inquiries and Complaints Greenpeace Ranks Electronics Manufacturers Standards List For The EU’s Energy Consumption Directive Published EU Commission Publishes Standards List for Directives on Pressure Equipment, Pressure Vessels Standards List for the EU’s Medical Devices Directive Available The IEEE Product Safety Engineering Society: The First Five Years ESD Open Forum Improving Election Security and Accuracy: The Future of Voting System Certification Conformity Assessment and Accreditation: Their Role in the Global Market Design Issues in Extreme EMC Environment Focus On... Test Equipment Buyers Guide Product News Updated Standards List for EU Directive on Active Implantable Medical Devices FDA Warns of Effects from CT Scans on Electronic Medical Devices FDA Provides Report Card on Its PMA Review Process CPSC Releases Import Safety Strategy Other CPSC Actions in the News IEC Standards Update Product Reviews UL Standards Update Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - October 2008

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