comment worth a further look

Hi Luke: > This won't work. If you want to look at how badly online forums work, look at the IEE website. Unfortunately, this requires a membership and a login. I really would like to know more about the success of web-based forums. Best regards, Rich

The listserver WILL continue.

Thank you for all the comments on the listserver- based service versus the web-based service. The IEEE listserver WILL continue. I apologize for not being clear on this point. We started with listserver service. However, the listserver does not satisfy all of the needs of our subscribers

Re: Death of the listserver

Hi Jim: Thanks for your message. > The EMC Laboratory that I work for (Acme Testing Company in Acme, > Washington) has the quietest open-field Emissions Sites (OATS) within a 1000 > mile radius. We planned it that way. The village of Acme has a total > population of under 100 peopl

Re: Leakage current test conundrum

Hi Charles: > a) Does anyone one know the genesis > of the requirement to lift the Neutral > AND the Ground simultaneously > during a leakage current test?? > (I am referring to UL6500) While I am not familiar with UL 6500 per se, I believe I can comment on the "lift" of the neutr

Methenamine timed burning tablet

Some fire tests use a "methenamine timed burning tablet." This tablet is specified in USA government standards for furniture flammablity testing. (See 16 CFR Part 1630.4 or CPSC standard FF 1-70.) It is also specified in ASTM D2859. I have also seen it used to test fire enclosures in Euro

Administrative message -- posting formats

Regarding postings, here is a re-statement of our guidelines that were sent to you when you subscribed: 1. No attachments (because many of our subscribers use dial-up modems for which message size determines the download time). If an attachment is appropriate or necessary to

docopocoss

"docopocoss" This word was unknown to me. I checked an American dictionary and could not find it. Then, I called up the Google search engine and entered the word, hoping to find an English dictionary. Google immediately came back with the definition. Rich --

Re: Value of Using Non-NRTL Engineering Firms?

Hi Chris: OSHA rules apply to employers. OSHA electrical rules require employers (1) to use only electrical products that have been certified by an NRTL, or (2) in the case of custom products, to test the product in place. If you sell a non-NRTL-certified "custom" product to an employer

Re: OFF is zero

Hi Stephen: > I think I missed the beginning of this thread, so > please forgive me if I rehash old ground. > > The 'vertical line' and 'circle' you refer to, are > actually a 1 ("One") and 0 ("Zero"); as in digital > logic on/off respectively. My original posting on this

Re: OFF is zero

Hi Serge: > O = Out of Circuit > I = In Circuit > > Note: while many people believe the symbols are O & 1, they are in fact > O & I IEC 60417 Symbols 5007 and 5008 are neither: the numbers 1 and 0, nor the letters I and O. They are the symbols depicted in the 60

Re: OFF is zero

Hi Neil: > The origin may be true, but IEC60417 is quite clear. ON is a vertical line > (symbol 5007) and OFF is a circle (symbol 5008). Agreed. And thank you for the clarification. Best regards, Rich --- This message is from the IEEE EMC

OFF is zero

A week or so ago, I asked about the origin of the 0 and 1 symbols for "off" and "on." I mentioned that it was my recollection that the the symbols came from early safety standards where the "off" and "on" functions were by means of a rotary switch where the 0/zero position was "off." I found

Origin of power symbols 0 and 1?

I am looking for the origin of the power symbols 0 (off) and 1 (on). The earliest standards that I have are CEE 10 and similar where the standard specifies something like: "Where a rotary switch is used for power, the 0 position shall be off and the 1 and higher position shall be o

Re: Creepage

Hi Richard: > What is a good source that explains the rational for the values for creepage > distances? There was a good deal of research done in the late '70s and early '80s on creepage distances and the deterioration due to deposition of foreign materials and the effects of humidity.

Re: Class III ID mark?

Hi Tom: With a bit further search, I found: http://w3.hike.te.chiba-u.ac.jp/iec417/html/doc/5180.html This site specifies the use and the referring standard: Application: On any kind of equipment. To identify equipment meeting the safety requirements specified for class

Re: Class III ID mark?

Hi Tom: > I guess what you think is IEC 60417 No. 5180, which shows "III" > in diamond shaped frame (45 degree rotated square). > (http://member.nifty.ne.jp/tsato/terms/iec417-5180.gif) Yes, this is the mark that was mentioned to me. > However, I don't know which standard require t

Class III ID mark?

A colleague recently showed me a Class III identification mark. However, he had no further information about the mark. (The Class III mark would be used to identify a Class III product similar to the way the Class II mark square-within-a-square is used to identify a double-insulated product.

EMC-PSTC now functional

The EMC-PSTC listserver was down from Friday afternoon until today, Monday, late morning (Pacific Daylight Time). If you attempted to post a message during this time, the message was lost. Please re-send. We apologize for the inconvenience. If you have any questions or comments about this

Changing our safety standards (was 0.1 uF discharge)

Hi Gert: > I also tried the discharge between two fingers, and found the result to > be unpleasant at least. > Time to change standards... Now we must ask the question: Is the purpose of the standard to prevent injury or to prevent an unpleasant experience? I presume tha

Changing our safety standards (was 0.1 uF discharge)

Hi Gert: > I also tried the discharge between two fingers, and found the result to > be unpleasant at least. > Time to change standards... Now we must ask the question: Is the purpose of the standard to prevent injury or to prevent an unpleasant experience? I presume that

Re: Question: Discharge capacitance 0.1 uF

Hi Tom: > So, for voltage up to 450V d.c. (i.e. up to 318V a.c.), capacitor > up to 0.1uF will become a Limited Current Circuit, hence the voltage > is not Hazardous Voltage (1.2.8.4) - no additional condition would > be required for the capacitor connected to the primary circuit. E

Re: safety testing in the USA

Hi Rob: > I am in discussions with a potential supplier of IT equipment, Its our > usual policy to request testing to a listed standard > such as UL 60950 for safety in North America. > > The supplier has replied that this is not mandatory. > > Is he correct? what compels saf

Re: Question: Discharge capacitance 0.1 uF

Hi Tom: > So, for voltage up to 450V d.c. (i.e. up to 318V a.c.), capacitor > up to 0.1uF will become a Limited Current Circuit, hence the voltage > is not Hazardous Voltage (1.2.8.4) - no additional condition would > be required for the capacitor connected to the primary circuit. El

Re: safety testing in the USA

Hi Rob: > I am in discussions with a potential supplier of IT equipment, Its our > usual policy to request testing to a listed standard > such as UL 60950 for safety in North America. > > The supplier has replied that this is not mandatory. > > Is he correct? what compels safe

Re: EN60950-1 Sect 2.5 Limited Power sources

Hi Tom: > Is it permitted to use PTC as an overcurrent protective device > for power sources not inherently limited? > I don't have EN60950-1 here, but I remember it must be a fuse > or other non-autoreset device. I said: "The trick is to determine if your test houses can

Re: Green/Yellow Earthing Leads

Hello from San Diego: One of our subscriber colleagues has pointed out that my assertion that Europe uses yellow as the color of the earthing wire is incorrect. I recall when the green-yellow was agreed to for power cords and internal equipment wiring. My recall was that both yellow and gr

Re: electric strength test

Hi Greg: > > >Why does "True SELV" require basic insulation > > >between SELV and earth? > > > > > >What is the hazardous voltage source, and what > > >is the current path through the body if that > > >basic insulation should fail? > > > > > > > > I believe (and I could

Re: EN60950-1 Sect 2.5 Limited Power sources

Hi Alex: > We use a linear (basically a transformer with a PTC thermistor) class II > SELV O/P stand alone power supply rated 10Vac, 5A. One of the labs tested > the O/P Isc with a direct application of the sc. The other lab tested the > O/P Isc by applying a load of 8A. The results w

Re: Green/Yellow Earthing Leads

Hi Peter: > What is the percentage of color over a surface area for the insulated > green/yellow earthing conductor. Is it better to have more yellow than green > or more green than yellow. I know North Americans prefer more green than > yellow and Europeans like more yellow than gree

Re: electric strength test

Hi John: > True SELV . requires double or reinforced insulation from hazardous > live parts/parts at hazardous voltages [different expressions used for > the same things] and basic insulation from earth. '950 SELV' allows SELV > circuits to be earthed (see 2.2.3.3 of IEC60950:1999

IT power distribution and Norway (was electric strength test)

Hi John: > >You may come across some distributors in Norway asking for DI or RI > >between PRI-EARTH, even for Class 1 power supplies. > > That's because Norway uses the 'IT' power distribution system, where > neither mains conductor is earthed directly, but one is earthed through

Re: electric strength test

Hi John: > That depends on which variety of SELV you mean. True SELV, as opposed to > '950 SELV', requires double or reinforced insulation from earth Why? Best regards, Rich --- This message is from the IEEE EMC Society Product Safety Technic

Re: electric strength test

Hi John: > >Y-caps have enough margin to easily withstand > >the 4300 V dc without damage. > > Without immediate failure, no doubt. But such a huge overstress may > cause latent damage that later results in failure, and, since IEC 60384 > doesn't call for such an over-voltage

Re: electric strength test

Hi Brian: > What I've always wondered about, at least for class 1 construction, is just > what is really being tested by the pri/sec hi-pot, when the customer chooses > to ground the power supply's return. (These comments presume the secondary is SELV.) When you use a ground for safe

Re: electric strength test

Hi Brian: > I am attempting to comply with both the letter and spirit of 60950:2000, cl > 5.2. Note that 5.2.2 allows for separate testing, according the type of > insulation required. When testing a (class 1) power supply, the withstand > level for primary to chassis is Basic; and f

minimum distance for PWB inner layers (was creepage)

Hi Tom: > In 60950, applicable clauses are 2.10.5.3 and 2.10.5.1 (I'm not > reading genuine IEC/EN 60950, and I'm sorry if I'm wrong) - > the former states that distance through insulation would be applied > in such situation, and the latter set minimum thickness of 0.4mm > for supp

Re: Creepage on PCB Internal Layers

Hi Chris: > To me, it's sort of funny in that it just says that the Creepage and > Clearance distances do not apply on inner layers of void free PCBs. > That's nice; but I can't find where a distance is specified. I mean, I > would think that there should be some minimum distance betwee

Re: Creepage on PCB Internal Layers

Hi Chris: > To me, it's sort of funny in that it just says that the Creepage and > Clearance distances do not apply on inner layers of void free PCBs. > That's nice; but I can't find where a distance is specified. I mean, I > would think that there should be some minimum distance betwee

Re: medical-grade transformers

Hi Ged: > "In transformers with REINFORCED INSULATION or DOUBLE INSULATION the > insulation between 1ary and 2ary windings shalll consist of - > - 1 insulation layer having thickness at least 1mm, or > - at least 2 insulation layers with total thickness not less than 0.3mm, or >

Re: Marking Languages for Canada

Hi Kris: > The markings on the power supply are: (also as per UL file) > Date code > model number > electrical ratings > "Class 2 transformer" > > The additional markings are: > "CAUTION", "Risk of electric shock" and "Dry location use only" and "Do not > expose to liquid,

Re: Marking Languages for Canada

Hi Kris: > A product from manufacturer X is delivered with a (direct plug-in) power > supply from mftr Y to customers in Canada. > Regarding the power supply, it is UL approved + UL listed and has the UL > marking with C and US. > The warning marking on the power supply is only in e

Re: Compliance Primer

It has been some time since I have had to explain or justify product safety activity to a high-level manager-type. As others have said, it is fraught with difficulties. Success depends on first determining the mindset of the person asking the question. I believe I would first ask a num

Re: Bonding Impedance

Hi Ron: Two years ago, Jim Bacher presented my paper, "Equipotentiality and Grounding -- Deriviation of Grounding Resistance for Equipment" at the IEEE EMC Symposium Product Safety Workshop. This paper is available for download from the IEEE PSTC Mindcruiser web site: http

Admin message: posted advertisement

Today, a message was posted that violates IEEE emc-pstc rules against advertising. Here is our rule: - 5. Blatant or overt advertising of goods or services is not permitted. The listserver is provided as a service by the IEEE, whose policies prohibit anything that might be c

Product safety job at Hewlett-Packard San Diego

Hewlett-Packard Company San Diego site is looking for a high-level product safety engineer. The major job function is that of advising product designers on 1) innovative safeguards for new products, and 2) safety certification requirements for new products. The ideal candi

Re: TOUCH CURRENT LIMIT

Hi Xing Weibing: > We can read from table 5A of IEC60950:1999: > > Touch current limit for accessible parts and circuits not connected > > to protective earth: 0.25 mA > > question 1 : How does it (0.25mA) come from and what it is based on? For grounded (Class I) equipment for the home,

10 watts (was IEC 60950 & Solar Cells)

Hi Ted: > it seems that the low voltage used in the application is being > mistaken for low energy. Your garden variety alkaline manganese cell > has such a low internal resistance that it behaves as a little bomb when > shorted. Same with lithium battery technology. If the solar cell can

Re: CCFT Backlight Circuits

Hi Chris: We use similar circuits. The circuit is an inverter powered from SELV. The inverter output is hazardous voltage. Usually, the output is floating, but not always. The output MAY be hazardous energy ONLY IF the SELV is hazardous energy. If the SELV is hazardous energy, the in

Re: UL 60950, Section 6.1.2.1

. Best regards, Rich > From douglas_beckw...@mitel.com Tue Jun 4 09:35:39 PDT 2002 > Subject: Re: UL 60950, Section 6.1.2.1 > To: Rich Nute > Cc: rgeorger...@carrieraccess.com, emc-p...@majordomo.ieee.org > Date: Tue, 4 Jun 2002 12:27:52 -0400 > > >

Posting available equipment, was Surplus EMC Test Equipment

The policy for emc-pstc postings allows for posting of availability of used or surplus equipment commonly used by subscribers to this listserver. (See the Charter that was sent to you when you subscribed.) However, the policy does not include advertising of any kind. So, how do we decide

Re: UL 60950, Section 6.1.2.1

Hi Richard: > For those who want to read the UL60950 Section 6.1.2.1, I have written the > specific parts of the section that I have questions on. Otherwise, here are > my questions and comments: > > 1) If the bridging components are left in place, do I still have to meet the > 1

Off-topic messages.

The subject matter for this forum is product safety EMC telecom and related issues. Off-topic postings dilute the value of this forum and are discouraged. I am declaring the subject of guns as off-topic. Further discussion of this topic may result in deletion from the subsc

Re: Anti-static Insulating Tape ???

Hi Doug: Thanks for sharing your findings on insulating tape and anti-static tape. All insulators have the property of insulation resistance. Modern insulations have insulation resistances in the gigaohm and teraohm ranges. I would guess that anti-static insulators have a relatively low va

Re: EMC and Class 2 equipment

Hi John: > Now we have sub-classes Y1 to Y4. Y capacitors can be used in locations > where neither side is grounded, but in the OP's context, grounding is > involved. What are the definitions of the various Y capacitors in the most edition of IEC 384? OP? > >A Y-cap can be used

Re: EMC and Class 2 equipment

Hi John: > >Ground connections is usually nice to have when dealing with EMC. But what > >about EMC and a class 2 (double insulation) power supply (shall comply with > >MIL-STD-461E) . I'm thinking on, what to do with the regularly Y-caps, > >does it really have any meaning with t

Admin message: RE: A very nice game virus.

Hi Chris, Bill, and all other subscribers: A message with the subject: A very nice game was sent to the IEEE (emc-pstc) for posting by our listserver. The original message contained a virus known as KLEZ.G. The IEEE computer detected the virus. This virus was stripped from the m

Re: EMC and Class 2 equipment

Hi Amund: Being a safety guy and not an emc guy... (disclaimer) > Ground connections is usually nice to have when dealing with EMC. But what > about EMC and a class 2 (double insulation) power supply (shall comply with > MIL-STD-461E) . I'm thinking on, what to do with the regular

Re: Criteria for UL V0 plastic enclosure

eet the HB flame class, hence my comment that he "may use any plastic." Best regards, Rich > Rich Nute wrote: > > > The choice is yours. If your product is supplied by a > > Limited Power Source, then you may use any plastic for the > > enclosure. If y

Re: Don'r Get Caught Running a Red Traffic Light!

Hi Doug: > I've only heard shortening the yellow light cycle > as an unconfirmed rumor. But I've been watching. > According to our local newspaper, the San Diego Union- Tribune, not only did the contract photo cops shorten the yellow light, they also moved the sensors. The contrac

Re: ventilation holes

Hi David: > You probably already know this, but don't forget that the product will need > to pass temp tests during abnormals i.e., blocked vents. I'm not sure if "pass temp tests" means compliance with the heating requirements or the abnormal requirements, so I offer this clarification

Re: UL Material flammability requirements for enclosures less than .3

Hi Paul: > Can anyone give me any information on whether a box with less than .33 cubic > feet needs to meet UL Flammability ratings? > I have been told this is true, but I can not find the location of that > information. I believe the requirement you are referring to is Sub-cla

Re: ventilation holes

Hi George: > I have a safety question for the group. I have a small (about 8 x 10 x 2 > inch) piece of ITE equipment, SELV, enclosed in a plastic case, powered by > an external 12 volt brick from AC mains. > > The problem is, the device tends to run a little hotter than desi

Re: double-pole switching and fusing

Hi John: > I read in !emc-pstc that Rich Nute wrote (in > <200202202227.oaa19...@epgc264.sdd.hp.com>) about 'double-pole switching > and fusing', on Wed, 20 Feb 2002: > >Tables 2E and 2F are invoked only by the Note 2 > >to Sub-clause 2.7.4. &g

double-pole switching and fusing

Hi John: > I read in !emc-pstc that Crabb, John > wrote (incr.com>) about 'South Korean Power System', on Wed, 20 Feb 2002: > >Typically I would expect IT equipment to be safe if line and neutral > >were reversed, except for the issues relating to a single pole > >disconnect de

Re: Using PCB traces as transient voltage suppressor

Hi Chris: > 1. Can anyone else verify the breakdown voltage of 1Megavolt/meter for > air? Seems different than what I can remember; but I don't have a > reference handy. It also seems to me that this would be very dependent > upon humidity and pollution degree? In a separate messa

Re: Safety of Indicating LEDs

Hi Scott: > The scope of EN 60825-1 says LEDs are included whenever the word "laser" > is used, meaning they are to be evaluated the same way lasers are. Does > this apply to status indicating LEDs (non-lasing)? If so, are > manufacturers expected to test every status-indicating LED

Re: South Korean Power System

Hi Ed: With few exceptions, most power distribution systems have one pole of the supply, the neutral, grounded. (Indeed, the definition of "neutral" for single-phase systems is the grounded conductor.) In the IEC scheme of the world, a power distribution system where the neutral is groun

Japan mains frequency

> A good source is http://kropla.com/electric2.htm > . > > According to that site: > Japan100V50/60 Hz* > > *Eastern Japan 50 Hz (Tokyo, Kawasaki, Sapporo, Yokohoma, and Sendai) > *Western Japan 60 Hz (Osaka, Kyoto, Nagoya, Hi

Admin message -- format of posted messages should be plain text

A request from your list administrators... > Except... I (and other classic Compuserve users) won't see these messages > at all, unless and until they appear in someone else's REPLY in a form > Compuserve can send. It LOOKS great - but please don't send HTML to the > list. Cortland is

Re: OEM

Hi Richard: > We may soon be privately labeling our products for a particular customer, > and I have a question concerning the EU Declaration of Conformity. We will > be shipping products to our customer's distribution center, and they will be > responsible for sales to their customer

Re: My subscription may have terminated

Hi Dan: > I have received no emails today. Did my subscription cease? No, your emc-pstc subscription is not terminated. Today is the most unusual day in the history of emc-pstc in that there were no postings to the listserver between 5:30 PM PST Tuesday and 11 AM PST Wednesday. I, too

Re: Flammabilty requirement for cloth used on loudspeaker / UL6500

Hi Pierre: > Unfortunately, Hexamine is temporarely unavailable from IMSPLUS, and, > furthermore, this product cannot be sold outside the US. > > If somebody knows another source, he's welcome ! I did a Google search and found at least one more source: http://www.omahas.com/sto

Re: Flammabilty requirement for cloth used on loudspeaker / UL6500

Hi Pierre: > Reading the standard, I understand that the cloth used on the front of the > loudspeaker (external to fire enclosure) has to be tested according the > "tablet test" (see Table 13). As I recall (from the UL standard), the tablet is hexamine. I have purchased tablets from:

Re: Teslars???

Hi Joe: > We have a customer that is concerned about how our product, laboratory > equipment, will respond to electromagnetic disturbances from a high speed > train that runs close to their lab. The customer states that the > disturbance will be around 0.7-1.2 m Teslar. I believe yo

Re: TUV NRTL

Hi George: > However, for the U.S. OSHA establishes acceptable NRTLs, and the > CFR uses the words "NRTL", so I do not see how an electrical > inspector could object to what the Federal Government has sanctioned. The inspector must abide by the certifications approved by the local bui

Re: CE Marking - Prototypes

Hi Gregg: > My understanding if that: > > where OSHA is applicable then UL or equivalent is mandatory. True. However, replace "UL or equivalent" with "NRTL." > where OSHA is not application then Local Code is mandatory - and LOCAL > Code > requires NRTL (UL or equivalen

Re: Telecommunications Vs. ITE Product

Hi Gregg: > Let me start by asking one simple question - WHAT IS THE PURPOSE OF > CERTIFICATION? > > 1- to meet the legal requirement > 2- help market the product > 3- do the 'right thing' > 4- not to kill anyone > 5- make sure that the product is nor recalled > >

Re: Harmonic current emissions

Hi John: > >> But whichever method is adopted, the customer pays the bill eventually > and I > >> have more confidence in the highly competitive world of electronic > products > >> to come up with a cost-effective solution in a timely manner. > > > >One of the USA's major ob

Harmonic current emissions

Hi Keith and Ghery: There are a number of effects of harmonic current emission from non-linear loads. 1) When a large number of loads rich in triplen harmonics are supplied from a 3-phase source, the neutral current can be as high as root 3 of the phase current. (This effect d

Re: Company close down due to EMC phenomena

Hi Amund: I suggest you and your client and the regulatory authority meet to address the situation. Here are the issues as I understand them from your message: 1. In idle mode, the emissions are comfortably below the maximum allowed emissions. 2. In transmit mode, the emissions exc

EMC-PSTC needs some help.

personally rewarding experience. If you would rather talk with our on-the-line admins, feel free to contact either one directly: Michael Garretson:pstc_ad...@garretson.org David Heald: dave_he...@hotmail.com Best regards, Rich and Jim Rich Nute: ri...@sdd.hp.com

Re: TR: 60950 - Insulation between mains and secondary with capacitors

Hi Pierre: You did not state whether or not your secondary circuit is intended to be SELV or not. This is critical to your choice of capacitor. However, you did ask whether the circuit is equivalent to reinforced insulation, so I assume that your secondary circuit is SELV. By definitio

Re: Switch Inrush Ratings

Taking John Woodgate's usual response to such an inquiry, I did a Google search on "inrush." Surprisingly (to me), there is a wealth of reasonably good info on the web under the subject of "inrush," including switches rated for inrush current. Best regards, Rich ---

Re: SMPS Derating reqs for Altitude range of 5000-10000ft

Hi Chris, Andrew, Carmen: With regard to safety, both effects of altitude must be considered: 1) effect of air pressure on the electric strength of air (clearance), and 2) effect of lower density air on the temperature of solid insulation. (Creepage is a surface

Re: EMC-related safety issues

> No, it's simply that it isn't considered reasonable to have a radio and > a CFL in close proximity. If you want a lamp and a radio close together, > use an incandescent lamp. That's the bottom line, isn't it? Somebody has decided for me (in terms of what is "reasonable") that if I u

Re: EMC-related safety issues

Hi John: > >I've replaced the incandescent lamp on my bedside > >table with a new energy-saving compact flourescent > >lamp. With the lamp on, I cannot listen to even > >the strongest AM radio station on my clock radio > >(on the same bedside table) due to the lamp > >interf

Re: EMC-related safety issues

Hi Ken: > Trial lawyers and their clients have an obvious interest in portraying > consumers as helpless and child-like, and rich corporations as robber-barons > preying on the poor and weak. But why does the rest of society jump on that > bandwagon? Because profit and wealth, once

Re: EMC-related safety issues

Hi Ken: > The Forrestal incident occurred during the Vietnam conflict, July 1967. It > was pretty much as you describe except I would not say EMI was not > controlled. All DOD services had EMI requirements at his time. In fact, > 1967 was the year that MIL-STD-461 was adopted as a

Re: EMC-related safety issues

Hi George: > The key word in EMC is "compatibility". This implies that electrical and > electronic > equipment are (ideally) designed so that each can operate normally in the > presence > of another. This requires limiting both the emissions and sensitivity of > such > devices.

Re: Electric Shock and Water

Hi John: > >Is there a value (or range of values) for the > > resistance of water? > > The data exists; it depends, of course, on solute nature and > concentration. Try a web search. I did a web search before my post. There is lots of data on the use of water resistance an

Re: Electric Shock and Water

Hi Jason: Water comprises a 3-dimensional resistor. The value of the resistor depends on: * the "purity" of the water itself (the resistance is inversely proportional to the purity); * the dimensions of the electrodes (i.e., the conductors in contact with the wate

Re: Fw: working voltage measurement

Hi Cortland: > One can also use a pair of probes known to be well balanced and take the > difference between the A and B channels, or > use a differential input accessory or plugin. There is then no possibility > of high-voltage on the instrument chassis. "Balance" is really Common-Mod

Re: Fw: working voltage measurement

Hi Xing Weibing: > 2. supply the SMPS from an isolating transformer where > both supply conductors are isolated from ground. > 3. connect secondary's ground and primary 's ground (neutral and ground > are connected together) This is the correct connection for measuring the prim

Re: Fw: working voltage measurement

Hi Xing Weibing: One of the problems of making oscilloscope measurements within switching-mode power supply circuits is that the common side of the oscilloscope *MAY* change the waveform. There are two ways to minimize the effect of the common side of the scope from affecting the waveform:

Re: Mains Cords in the UK and the fuse rating

Hi John: > More significantly, its resistance affects the maximum short-circuit > current that can flow. This is a valid consideration with regard to safety. Given a 6-amp maximum, 0.75 sq mm size, and 2 meters length. In North America, 2X rated current is the 1-minute operating time

Re: Mains Cords in the UK and the fuse rating

> For an IT product there is a restriction in the use of mains cords with a > cross > sectional area of 0.75mm2 for units up to 6 amps when the cord is greater > than > 2m in length (EN60950: 2000 section 3.2.5) I am curious as to the hazard that is prevented by this length require

Re: [Fwd: clearance and working voltage]

Hi Xing Weibing: Here is my answer to the question. >Hi group I have a question regarding clearance and working voltage of > IEC60950. If I HAVE A AC ADAPTER(AC 100-240V 50/60Hz) ,THE WORKING > VOLTAGE MEASURED ARE AS FOLLOWS: Nominal supply voltage: AC240V PRIMARY > AND SECONDARY

Re: Quality Assurance and Product Approvals

> On the aspect of the "where to put Product Safety/Compliance in the > organization" discussion bears mentioning on the forum. In general I > advocate that the Product Safety/Compliance department be separate from > Engineering, Sales, and Operations. The Safety/Compliance group sho

Re: Production Line Hipot Test for Network Powered Equipment

Hi Jerry: > Will a production line hipot test be required? As far as I know, the only certification house that requires a production-line hi-pot test of TNV circuits is UL. The test is specified in the gray pages as a separate test from that of the mains hi-pot test. Since you mentione

Re: Quality Assurance and Product Approvals

Hi Dan: > Dell Computers, as well as a few other major players, take a proactive > approach to compliance and actually have a VP position for compliance. With > a little investigation into the benefits of having a first rate compliance > department with the ability to design for compl

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