Conformity Magazine - November 2007 - (Page 55)

I remember vividly standing at the Northeast Product Safety Show, overhearing two gentlemen discussing how high tech the new hipot testers are. One commented that all his “legacy” hipot testers worked with only a variable transformer and a voltmeter. Yes, hipot testers have come a long way. Today’s testers provide more function than the single high voltage AC or DC test. The features within a new hipot tester have been added due to demand from the industry and most importantly safety. This article will discuss the use of the features that have brought the hipot tester into the 21st century, and which features to pay attention to when buying one. Hipot tests are performed in production to meet safety standard requirements. Each product has a test standard whose specifications must be met. The first step in selecting a tester is to determine the primary as well as the supplementary test standards. Tests such as Ground Bond, Ground Continuity, Insulation Resistance, and Leakage Current are required for most product safety compliance. Some standards may require these tests for production also. If your company decides these are tests you want to perform, look for test equipment that can accomplish all of the tests in one instrument. The Tests Dielectric withstand, high potential voltage breakdown, or hipot tests stress the insulation of a product beyond what it may encounter in normal use. This test is performed using AC or DC voltage. The safety standard can call for AC or DC testing or both, depending on the specific product type. AC is often specified more than DC and can be more stressful. For example, power line consumer products are much more likely to experience AC voltage transients than DC transients. Typically a product powered by AC is tested with AC, and a product powered by DC is tested with DC. waiting for the charge current to reduce after each step. If the current suddenly rises, a breakdown may be on its way. By stopping the test at this point, destruction of the material can be prevented. However it does not tell where the breakdown would have occurred. Ground Continuity, very common in production testing, is performed using a low DC current source, typically less than 1 Amp, between the ground blade on the power cord and any exposed metal on the product. Most hipot testers come standard with a ground continuity measuring circuit. Ground Bond is not always required for production testing but some manufacturers choose this test over Ground Figure 1: Ground fault interrupt Looking for EMC Test Equipment? www.atecorp.com A Wide Variety of Test and Measurement Equipment Available When You Need It, As Long As You Need It! AC testing has some advantages over DC testing as it stresses the insulation equally in both polarities, whereas DC testing stresses the insulation in single polarity only. There is not a charge time associated with AC and it is not necessary to discharge the product after testing. However, AC can have a downfall if the device under test is capacitive. The reactive current (caused by the capacitance) is typically much higher than the real current, resulting in the total leakage current to be comprised mostly of reactive current. An increase in real current may go undetected due to the magnitude of the www.atecorp.com reactive current. If an AC test is required and the DUT has capacitors, ensure that the tester you choose has high output current capacity. Performing a DC test may be a better option than running the device at high unsafe currents. Performing a DC test may take longer because the device needs to charge, but once fully charged, the leakage is true leakage. This provides a more realistic indication of the quality of the insulation of the product. DC is also used in non-destructive testing of devices for predicting when a breakdown occurs. This is done by raising the test voltage in small increments and Advanced Test Equipment Rentals Transient / Surge / EFT Generators Spectrum Analyzers / Receivers Antennas / Sniffer Probes Amplifiers Bulk Current Injection Probes Couplers / CDNs / LISNs ESD Simulators / Guns Rentals Leases Sales www.atecorp.com RENT Today! SOLVE Tomorrow! Fast Shipping / Technical Support / Custom Solutions Full Online Catalog Available at www.atecorp.com Agilent A.H. Systems Amplifier Research Haefely IFI Narda Rohde & Schwarz Schaffner and more Advanced Test Equipment Rentals www.atecorp.com (800) 404-2832 CONFORMITY www.atecorp.com NOVEMBER sales@atecorp.com 55 2007 http://www.atecorp.com http://www.atecorp.com http://www.atecorp.com http://www.atecorp.com http://www.atecorp.com http://www.atecorp.com

Table of Contents Feed for the Digital Edition of Conformity Magazine - November 2007

Conformity - November 2007 Contents Editor’s Note Commission Sets Date, Terms for 700 MHz Auction FCC Reaffirms Roaming Obligations Commission Moves to Improve USF Management FCC Proposes Fines for Violations of E911 Handset Requirements Commission Levies $1 Million Plus Fines for Unsolicited Fax Advertisements GR-3150 - Lithium Battery Certification Levels Based on Criteria for General Product, Safety, and Performance, Part 2 ESD Open Forum Machinery Field Evaluation for the United States Validation, Verification, and Immunity Testing Techniques for EMC for Functional Safety Thermal/EMC Simulation Addresses New Mechanical Design Challenges Product Safety Equipment Buyer’s Guide FCC Releases Report on Telephone Numbering Resource Utilization Canada Still Has PCS Spectrum to Assign Updated Standards List for the EU’s Medical Devices Directive Updated Standards List for EU Directive on Active Implantable Medical Devices Call for Papers for the 2008 EOS/ESD Symposium Announced Mobile Phone Use in Hospitals May Be Dangerous CPSC Actions in the News IEC Standards Update UL Standards Update Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Product Reviews Looking Back: Items from Past Issues of Conformity Upcoming Events Advertisers

Conformity Magazine - November 2007

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.