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Electrical Safety Testing
General
Q1. Why do products need to undergo electrical safety tests? Why do products need to undergo electrical safety tests?
This question is many manufacturers want to ask, surely the general answer is “because it is regulated in safety standard”. If you can deeply realize the background of electrical safety then will find the concealed responsibility and meaning behind it. Although electrical safety test occupies a little time on production line, yet it let you reduce the risk of reclamation cause by electrical haza
Q2. What does the chapter on safety standard include? What does the chapter on safety standard include?
The chapter of safety standard includes introduction, meaning, performance test, production test, label and appendix. For electrical safety test, the most important is performance tests and production tests, performance tests are testing all of primary products consist of electric hazard, energy, fire and mechanical hazard. These tests also write in production tests but part of test can't use on production line because of time-consuming. Thus, part of safety standard divides performance tests and production tests for describing. The quality of safety standard decides safety coefficient of product, for example medical equipment usually contact with patient thus its’ safety coefficient should be higher than other products.
Q3. What is Electrical Shock ? What is Electrical Shock ?
The factor for causing electrical shock has several types, the mainly electrical shock is caused by current through human body. This kind of electrical shock has direct effect on human body, the differences of injuring serious depends on degree of electrical energy, humidity and touch area. Image you are bathing in bath tube, suddenly drier in operating dropping into bath tube, the current flows from drier through your body to ground under this situation. Meanwhile, your heart palpitation un-regulated and blood pressure falling down causes tragedy can't be redeemed.
Q4. What are the major tests in Electrical Safety Test? What are the major tests in Electrical Safety Test?
Electrical shock includes the following four kinds of test.
  • Dielectric Withstand / Hipot Test: Withstand test apply high voltage on power and ground terminal circuit of product to measure its collapse status.
  • Isolation Resistance Test: Measure product electrical isolation status.
  • Leakage Current Test: Inspect whether leakage current of AC/DC power flows to ground terminal is over standard.
  • Protective Ground: Inspect whether metal mechanics of accessible part surely grounding.
    • Q5. How to Select the Correct Safety Test Equipment How to Select the Correct Safety Test Equipment
    The first step to select safety test equipment is to realize your basic requirement, it may be the safety standard your company product need to accord. The test is for promoting product function requirement and consideration of cost and efficiency. The excellent safety test equipment is not only in accordance with related safety standard of test equipment but also reach correct and efficiency test for test item, test output range and requirement of various products. Auxiliary accessory, fixture and software control of laboratory, production line can promote test efficiency, like as high voltage gun, air power equipment and remote control box can direct control trigger by interface of test equipment or control by interlock. It is not only decrease electrical shock to personnel but also increase the efficiency of production line automation.
    Q6. Why do we need a better discharge circuit in Electrical Safety Tester? Why do we need a better discharge circuit in Electrical Safety Tester?
    Almost all of DUTs are equipped with capacitance and occurred charge condition when DC tests. For avoiding test personnel electrical hazard is occurred, it is necessary to discharge to regulation voltage value when test is ended. However, the higher of capacitance and the longer of discharge time it affects the smooth of production directly. The excellent safety test equipment is equipped with reliable and fast discharge circuit for the manufacturers bring the efficiency of economy.
    Q7. How to ensure the test connection is OK How to ensure the test connection is OK
    It may occur DUT no contact or bad contact condition during test procedure, especially in production line of emphasizing efficiency occurs more easily. The DUTs which are no contact, bad contact, test line damage or short circuit will judge no good product as good product or damage the equipment then cause the unnecessary risk cost. Thus, a lot of safety test equipment will judge if there is bad contact by low limit or high limit of current, this method interference factor too much so can’t judge effectively. The excellent safety test equipment filter short circuit DUT or judge circuit bad contact by more accurate judgment method (OSC) to save the production cost of manufacturers.
    Q8. Why do the electrical safety test operators need more Training? Why do the electrical safety test operators need more Training?
    All personnel of operating test equipment need to accept basic electronic theory training to realize the effect of current on human body and how to avoid electrical shock, familiar with test environment and precaution for emergency condition occurred. Some test equipments are with interlock function to prevent improper operation. When the personnel realize the previous described items then to explain operation procedure and test purpose about the condition of no good product and test fail occurred. Since the safety tests mostly are high voltage or mass current test, the test personnel should be pay more attention while testing.
    Q9. Is there any special requirement for Test Environments? Is there any special requirement for Test Environments?
    In Europe, the safety for manufacturers and test personnel of laboratory had performed for many years. The manufacturers and test personnel of electronic appliances, technology product, household appliances, mechanical tool or miscellaneous equipment, there is chapter to regulate in various safety regulations. The contents of UL, IEC and EN include grounding status of test area marking (personnel, instrument and DUT position), equipment marking (marked with "dangerous" specifically or the item in testing), equipment worktable and etc and electrical insulation capability of various test equipment (IEC 61010).
    Q10. Safety Information Website Safety Information Website

    UL

    www.ul.com

    American Underwriters Laboratories Recognized Administration

    ANSI

    www.ansi.org

    American National Standards Institute

    BSI

    www.bsi.org.uk

    British Standards

    CENELEC

    www.cenelec.org

    European Committee for Electrotechnical

    CSA

    www.csa.ca

    Canadian Standards Association

    VDE

    www.vde.de

    Germany Electronic Electrical Information Association

    IEC

    www.iec.ch

    International Electrotechnical Commission

    JSA

    www.jsa.or.jp

    Japanese Standards Association

    IEEE

    www.ieee.org

    American Institute of Electrical and Electronics Engineers, Inc.

    ISO

    www.iso.ch

    International Organization for Standardization

    OSHA

    www.osha.gov

    American Occupational Safety & Health Administration

    TUV

    www.tuv.com

    German TUV Recognized Administration

    CCC

    www.cccn.org.cn

    People’s Republic of China Enforced Product Recognized Center

    NSSN

    www.nssn.org

    National Resource for Global Standards

    BSMI

    www.bsmi.gov.tw

    Bureau of Standards, Metrology & Inspection, MOEA, R.O.C

    Chroma

    www.chromaate.com

    Chroma ATE INC.
    AC/DC Dielectric Withstand Test (HIPOT Test)
    Q1. What is Dielectric Withstand Test? What is Dielectric Withstand Test?
    Hipot test is one of safety test being often seen. Often seen dielectric withstand, high potential and hipot test all denote withstanding test. The mainly purpose of hipot test is for testing insulating capability of DUT(Device under Test). When the equipment is operating, apply a high voltage to test point for testing whether insulation breakdown or electrical flashover/ARC are occurred.
    Q2. How many types of isolation are there in Safety Standards? How many types of isolation are there in Safety Standards?
    The insulation is divided into four types: Basic, Supplementary, Double and Reinforced. Because product inside may be over dirt, wet or other reason cause discharge along surface, thus judge if circuit design inside product has problems of distance along surface or insulation insufficiency by hipot test.
    Q3. Why do we need real current function in AC Hipot test? Why do we need real current function in AC Hipot test?
    Please notice that may has difference between total current and real current cause by partly internal capacitive reactance. The curent is outputting, if capacitive reactance is higher and reactive is higher, this makes real current lower relatively. If the user can’t measure output current accurately, it will cause a blind spot in testing.
    Q4. Why do we need ramp time in DC Hipot test? Why do we need ramp time in DC Hipot test?
    DC hipot test usually need to add ramp time and fall time, because mostly DUTs are with capacitance and causes charging current generated(figure 3). For charging current steady, ramp time is needed for buffering then leakage current won’t over high because of charge current and judge as FAIL
    Q5. Why do we need fall time in Hipot test? Why do we need fall time in Hipot test?
    Because hipot test will cause DUT discharge, thus need a period of time for discharging after hipot test is ended. A fine hipot test equipment will descrease fall time to the minimum and mark danger warning before reaching discharge standard for protecting the testers from electrical shock
    Q6. What is flashover (ARC)? What is flashover (ARC)?
    Obviously indicate that can't occur breakdown in safety standard and partly safety standard request can't occur Flashover/ARC(figure 4), and without definite test standard. ARC belongs to a kind of electrical discharge, when ARC occurred it means insulation capability insufficient. If ARC occurred several times then it will result in breakdown.
    Q7. Why do we need Auto Gain Compensation? Why do we need Auto Gain Compensation?
    The test voltage of standard is the mainly factor for judging good product in hipot test. A lot of hipot test equipment convert low voltage into high voltage by transformer then output it, but internal impedance of instrument will cause divider especially in some bad quality hipot test equipment, its actual output voltage can't reach safety standard. For avoiding error to judge as good product and cause unnecessary trouble, fine hipot test equipment will auto gain compensation to modify and compensate voltage to needed voltage value and design the voltmeter on the output terminal for measuring accurately whether output voltage is insufficient
    Ground Bond Test
    Q1. What is Ground Bond Test? What is Ground Bond Test?
    Ground protection consists of two kinds of test method: Ground Continuity test (GC) and Ground Bond test (GB). The purpose of ground protection test is for protecting users from electrical hazards as touching equipment when unsuitable current is created and flows to the earth.
    Insulation Resistance Test
    Q1. What is Insulation Resistance Test? What is Insulation Resistance Test?
    Insulation resistance test and DC withstand test are very similarity, apply DC voltage (50~1000V) to two points of connecting for judging good and no good product. Insulation resistance test is nondestructive test and can detect if insulation is good. In some regulation, do insulation resistance test firstly then withstand test. When insulation resistance test can't pass usually withstand voltage test also can’t pass.
    Leakage Current Test
    Q1. What is Leakage Current? What is Leakage Current?
    The current is brimmed over as flowing through insulation impedance we called it leakage current, contact by human body and the current through human body flow to Earth then electrical damage is occurred. The difference between leakage current test, withstanding voltage test and grounding protection test is equipment testing under running status. The leakage current adds a human body simulation impedance circuit in testing, it can simulate the quantity of leakage current through human body under real condition.
    Q2. What are the different types of insulation? (Class I, II, III) What are the different types of insulation? (Class I, II, III)
    Whatever national standard regulation or region standard regulation, the standard of leakage current is different by the insulation types of products. “CLASSI, II, III” are mainly in consideration of the insulation system of product which derived from IEC system, brief descriptions are as below:
    • CLASS I indicates anti-shock protection of product not only depends on basic insulation but also includes grounding method.
    • CLASS II indicates anti-shock protection of product not only depends on basic insulation but also includes additional precaution. For example double or reinforce insulation but without grounding or installation condition for relying precaution.
    • CLASS III indicates anti-shock protection of product depends on power voltage is safety extra-low voltage (SELV) and it don’t generate danger voltage.
    Q3. How many types of leakage current tests are in the standards? How many types of leakage current tests are in the standards?
    The leakage current with different test mode by various safeties and different leakage current standard by various test point. The most often seen is that the current flows through DUT to E terminal of power, the human body touches E terminal of product will cause induction we called it earth leakage current. When earth leakage current is testing input 110% rated voltage to add human simulation circuit and judge if the current value of flowing through human simulation circuit is over the limit value of leakage current. In addition, there are Patient Leakage Current, Patient Auxiliary Leakage Current and etc leakage tests.
    Q4. Why are leakage current tests so important in Medical Equipment Safety Standards? Why are leakage current tests so important in Medical Equipment Safety Standards?
    The definition of medical equipment is the physical or electrical contact with patients (mostly regulations denotes human being, Europe regulations denotes human being and animal), applies to the equipment of diagnosing, treating and monitoring. The leakage current testing of medical equipment emphasizes on Applied part under normal using status by physical method to contact patient or accessories and facilities the patients need to touch such as probe, electrocardiogram, blood pressure bar and operating table. All types of leakage current will cause electrical hazards to patients and operators.
    Q5. What is earth leakage current? What is earth leakage current?
    The current flows from the power terminal through DUT to E terminal of power as product running.
    Q6. What is Enclosure / touch Leakage Current? What is Enclosure / touch Leakage Current?
    The current flow from two kinds of power terminal through DUT to accessible part of chassis, touch point and screw products, created inductance as human body touch, we called it enclosure/touch/chassis leakage current.
    Q7. What is patient leakage current? What is patient leakage current?
    Patient leakage current consists of three kinds of test. The first test is the current flow from power terminal through applied part to earth terminal as product operating;Another test of patient leakage current, power source applies to MD by 110% the highest operating voltage. Make the current flows through applied part, accessible part then to earth terminal;The third test of patient leakage current, power source applies to SOP/SIP by 110% the highest operating voltage. When the product is operating, the current flows from two kinds of power terminal through applied part, MD then to earth terminal.
    Q8. What is Patient Auxiliary Leakage Current? What is Patient Auxiliary Leakage Current?
    When the product is operating, the current flows from test point of applied part through MD to another test point of applied part then to earth terminal
    PXI Instruments and Systems
    General
    Q1. How reliable is your product? How reliable is your product?
    Chroma ATE is the premiere instrument maker in Taiwan. All of our products must go through ISO9001 certified design process, and must pass Highly Accelerated Life Testing (HALT) before production. All products are built in house, with our own SMT lines for quality control.
    Q2. I want to know how you can support me on production environment. I want to know how you can support me on production environment.
    Well, PXI is well suited for production T&M because of its plug-and-play feature. At Chroma, all the plug-in cards are Hot Swappable, so the production down time is minimized. Furthermore, all of our relay products uses two boards. All the control circuit is on the main board, and all the relays are on the daughter board. As you know relays go bad after awhile, and our approach made customer repair much easier.
    Q3. Why should I buy relay products from Chroma? Why should I buy relay products from Chroma?
    I would say VALUE. Our relay cards are every bit as good as others. We are also a good PXI citizen, our relay cards can be triggered via trigger bus, via external trigger, or under software control. All our relay products also have programmable delays, a must in critical applications.
    Automated Optical Inspection
    Sub-Nanometer 3D Optical Profiler
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