tag:blogger.com,1999:blog-47925221505830385792010-05-12T10:11:29.010-04:00High VoltageHigh voltage reference information, with issues relating to high voltage power supplies, transformers, capacitors, resistors, diodes and other components. Also included are high voltage design, various applications, safety, corona, and standards. See the <a href="http://www.highvoltageinfo.com">high voltage information website.</a> <a href="http://www.digg.com">
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</a>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.comBlogger92125tag:blogger.com,1999:blog-4792522150583038579.post-12071934155930217222009-07-23T10:39:00.004-04:002009-07-23T11:02:11.449-04:00Build Your Own High Voltage Optocoupler<a href="http://www.highvoltageinfo.com/uploaded_images/VMI-OZ100SG-opto-717067.JPG"><img style="MARGIN: 0px 0px 10px 10px; WIDTH: 100px; FLOAT: right; HEIGHT: 100px; CURSOR: hand" border="0" alt="" src="http://www.highvoltageinfo.com/uploaded_images/VMI-OZ100SG-opto-717066.JPG" /></a><br /><div>Have you ever needed an optocoupler or isolator but couldn't find what you needed? If so, you might have an interest in Voltage Multipliers' new OZ100SG 10kV opto-diode. This device makes it possible to build your very own high voltage opto-coupler using your choice of LEDs as a light source. Simply reverse bias the photo-diode, run forward current through one or more LEDs (thus exposing the photo-diode junctions to light), and monitor the leakage current, Ir. The level of leakage current serves as feedback for forward current through the LED, while providing system isolation. For more information see <a href="http://www.voltagemultipliers.com/Aliases/LPs/highvoltageinfo.html">Voltage Multiplier OZ100SG</a></div><br /><div></div><div></div><div></div><div>The OZ100SG represents a breakthrough in opto-diode technology. Capable of operating at up to 10,000 volts reverse bias (10kV Vrwm) is it comprised of multiple silicon junctions. The key to operation is light sensitive junctions. Molded in optically clear epoxy, the OZ100SG is a light-sensitive device. When exposed to light, leakage current, Ir, is the result. Leakage current is directly proportional to light intensity, so by varying forward current through the LEDs, light intensity from the LED will vary.<br /></div><br /><div>Varying light intensity in the LEDs results in a corresponding variation in Ir in the photodiode. Ir typically ranges from 1uA to 1nA range. Controlling the exposure to light makes it possible to control leakage current in the photo-diode, thus providing a closed feedback loop. This makes for a useful way to remotely monitor electronically sensitive systems. </div><br /><div><br />Other light sources can be used to generate leakage current in the photodiode. </div><br /><div></div><br /><div>Applications include</div><br /><div>• High Voltage Switches and Remote Control Circuitry</div><br /><div>• HV Linear Regulators</div><br /><div>• Spectroscopy</div><br /><div>• Pockels Cells</div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-1207193415593021722?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com23tag:blogger.com,1999:blog-4792522150583038579.post-2479151088730597352008-12-18T11:35:00.002-05:002008-12-18T11:51:46.926-05:00High Voltage WineApplying a high voltage electric field can shorten the ageing process of wines. Research has been underway for ten years. Taste tests by a panel of experts indicate that this works. <br /><br />The best results appear to occur with a field strength in the range from 300Vac/cm to 600Vac/cm. Details of the plug-in ageing process have been reported in New Scientist magazine. ''Not only can it shorten a wine's normal storage time, it can also improve some lower-quality wines,'' according to the New Scientist article.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-247915108873059735?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-62399573930628741572008-11-24T10:52:00.001-05:002008-11-24T10:52:01.074-05:00Ultra-High Voltage Transformer<a href="http://www.highvoltageinfo.com/uploaded_images/Siemens-UHVDC-Transformer-707863.bmp"><img style="FLOAT: right; MARGIN: 0px 0px 10px 10px; WIDTH: 200px; CURSOR: hand; HEIGHT: 174px" alt="" src="http://www.highvoltageinfo.com/uploaded_images/Siemens-UHVDC-Transformer-707843.bmp" border="0" /></a><br /><div>A new transformer developed for the world’s first ultra high-voltage DC transmission systems (UHVDC) has successfully completed final testing. It is the first transformer for the new 800 kilovolts (kV) HVDC in China. Today’s HVDC transmission systems normally operate at a standard transmission voltage of 500 kilovolts. HVDC systems can transmit power over much greater distances and at considerably reduced loss than is possible with AC systems.<br /><br />To achieve this 60-percent increase in peak voltage capacity, Siemens had to develop a range of entirely new technical solutions for the new 800-kilovolt HVDC transmission system. One of several major challenges facing the company’s development engineers in Nuremberg was a lack of any defined standards for this scale of system. Due to the very high operating voltage, for example, they had to design exceptionally effective insulation systems. Therefore, in order to achieve the needed insulating clearances in air, the two valve bushings through which the current flows from inside the transformer to the converters are 14 meters in length. To construct the 800 kV transformers, a new, specially air-conditioned production hall had to be built to prevent the insulation from absorbing moisture from the atmosphere during final assembly. Similarly, the test facility in the Nuremberg factory had to be adapted to accommodate the tremendous increase in voltage when carrying out final acceptance testing on the new transformer.</div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-6239957393062874157?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com4tag:blogger.com,1999:blog-4792522150583038579.post-25642523010062569302008-11-17T09:29:00.000-05:002008-11-17T09:30:23.477-05:00High Voltage Curve TracerAgilent Technologies Inc. recently introduced the industry's first power device analyzer/curve tracer able to characterize semiconductor devices at up to 3,000 volts and 20 amps.<br /><br />Power devices, including power management ICs (PMIC) and power MOSFETs and motor control ICs used in cars, are a growing device category that requires both high-power and high-accuracy test. In order to meet emerging standards for low-carbon emissions and improved energy efficiencies, power devices must function more efficiently even as they continue to become more complex, smaller and faster. New devices using wide band gap materials such as silicon carbide (SiC) or gallium nitride (GaN) have been widely studied in order to achieve high efficiency. To enable the careful and precise testing to meet performance and safety requirements, these studies require high-voltage measurement capabilities greater than 1,000 volts. In addition, for those power-device developments, on-wafer testing becomes very important for reducing development turnaround times.<br /><br />Featuring a curve tracer mode, the Agilent B1505A can replace curve tracers used in failure analysis, as well as in circuit design or power module development of electronic equipment makers.<br /><br />Key Features of the Agilent B1505A Power Device Analyzer/Curve Tracer usful to high voltage engineers:<br />-- Accurate measurement of breakdown voltage and leakage currents at high voltage.<br />-- Sub picoamp level measurement capability at high voltage.<br />-- Capacitance-Voltage (CV) measurement with up to 3,000 V bias.<br />-- Device characterization at 3,000 volts and 20 amps in a single instrument.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-2564252301006256930?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-54273856167960997732008-10-24T16:20:00.000-04:002008-11-17T09:37:27.467-05:00High Voltage DC Leakage TesterThe newly introduced Model PT-5000W High Voltage DC Leakage Tester from HC Electric is a general purpose dual voltage leakage tester designed to test equipment for faults or high leakage currents. The test voltage can be set by the user to either 500 VDC or 5,000 VDC.<br /><br />The handheld PT-5000W can be used to check for leakage on cables, transformers, capacitors, joints, terminations, insulators, etc.<br /><br />Key Features:<br />• Portable unit tests de-energized and discharged capacitors, transformers, terminations and insulators<br /><br />• Use in overhead or underground systems<br /><br />• User selectable - test 500 VDC or 5,000 VDC<br /><br />The PT-5000W can only be used on cables or equipment that has been verified to be de-energized and discharged. primary distribution voltage or secondary voltage. For further info, see <a href="http://www.hdelectriccompany.com/pt5000w.htm">http://www.hdelectriccompany.com/pt5000w.htm</a><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-5427385616796099773?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-51991366822278538152008-09-10T14:59:00.000-04:002008-09-10T14:59:00.643-04:00Insulation TestingInsulation testing is often seen as the third core test and is usually preceded by an earth bond and a flash test.<br /><br />The insulation test measures the resistance of a product's insulation protection by applying a DC voltage between phase and neutral to the earth conductor for Class I equipment and between phase and neutral to the outer case for Class II equipment. This will show a reading of resistance in Mohms.<br /><br />The test ensures protective insulation is good enough to form a barrier to make sure people aren't electrocuted and to ensure other manufacturing systems and machinery are not affected.<br /><br />Legislation such as the low voltage directive (LVD) requires evidence of due diligence and the results of this and the in-service test can be used as well.<br /><br />The test can be applied to both Class I and Class II equipment and should be carried out using probes or insulated clips and without the equipment being connected to a power supply.<br /><br />Test voltages vary between standards - although 500V DC is the most common application - and the voltage is applied for a maximum of three seconds.<br /><br />However, electrical safety testing specialists Clare Instruments has designed test equipment for supplying up to 1000V where greater protection is called for (for example in automotive industry ignitions).<br /><br />Equipment has also been supplied with voltage as low as 100V where higher voltages may cause damage (for example in motor industry switches).<br /><br />In general, pass/fault limits for Class I equipment is a resistance greater than 2Mohms and for Class II equipment is a resistance greater than 7Mohms.<br /><br />There are differences in the flash/hipot tests - flash testing detects gaps or clearance between conductive parts and earth, pin holes in insulation and other degradation that may be the result of production processes and/or wear and tear, while insulation resistance testing is designed to provide a quantitative measurement of the quality of insulation.<br /><br />If a wire was positioned 0.5mm from exposed metal, an insulation test conducted in dry air could provide a pass reading.<br /><br />However, a flash test is more likely to detect if this situation was dangerous.<br /><br />Similarly, if insulation is somehow contaminated, a flash test would produce a pass, but an insulation test would highlight the deficiency.<br /><br />For example, the normal minimum insulation resistance value for Class I appliances is 2Mohm, but with a 1,500V AC flash test, the current would be 0.75mA and would not be detected by the 5mA trip, which has to accommodate the capacitive losses that occur.<br /><br />A DC flash test with a leakage meter can provide insulation resistance monitoring, as the capacitive component is leveled out after the initial switch-on surge.<br /><br />The test time of two to three seconds does not generally pose a problem on the production line, but some practicalities need to be addressed.<br /><br />For example, the use of a conductive foam nest can aid the testing of Class II products, and this nest can be integrated with test enclosures and probes.<br /><br />Typical causes of insulation test failure include poor quality insulating materials, material that has been over-stressed either mechanically or electrically, poor maintenance and cleaning procedures, ingress of fluids and dust, and assembly faults.<br /><br />For more information, request a free brochure from Clare Instruments, where this article is from.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-5199136682227853815?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-32257118813269362162008-08-29T15:19:00.000-04:002008-08-29T15:23:47.320-04:00Isolated High Voltage DC-DC convertersTwo isolated dc-to-dc converters with high isolation voltage have come to our attention recently. Providing low voltage power that floats at a high voltage can be tough to implement. <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">However</span>, these products can do just that, and they do in in compact packages.<br /><br />One is a 1W single or dual output unit with 15<span class="blsp-spelling-error" id="SPELLING_ERROR_1">kVdc</span> isolation. It is supplied in a DIP package. Very handy. For more information on this, please contact us at <a href="mailto:fred@highvoltageinfo.com">fred@highvoltageinfo.com</a><br /><br />The other is a 0.5W single output unit with 2.5<span class="blsp-spelling-error" id="SPELLING_ERROR_2">kVac</span> isolation. It is the Analog Devices <span class="blsp-spelling-error" id="SPELLING_ERROR_3">ADUM</span>5000 Isolated DC/DC Converter. Note that this product is not yet released to manufacturing, so it it worth checking further into availability of this announced part.<br /><a href="http://www.analog.com/en/prod/0,2877,ADUM5000,00.html?ref=ASC-LH-263"></a><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-3225711881326936216?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com1tag:blogger.com,1999:blog-4792522150583038579.post-53347635974764027942008-08-06T17:44:00.001-04:002008-08-29T15:18:41.858-04:00High Voltage, Low Noise DC/DC Converter Circuit DesignsHave you seen the Linear Technology application note on high voltage, low noise DC/DC converters? <span class="blsp-spelling-error" id="SPELLING_ERROR_0">Ap</span> notes don't get any better than this one. It includes circuits for high voltage power supplies rated from 200V to 1000V. It also addresses noise issues, and the effects of various voltage feedback techniques on transient response.<br /><br />The <span class="blsp-spelling-error" id="SPELLING_ERROR_1">ap</span> note describes resonant <span class="blsp-spelling-error" id="SPELLING_ERROR_2">Royer</span> topologies (which produces power by utilizing <span class="blsp-spelling-corrected" id="SPELLING_ERROR_3">sinusoidal</span> waveforms instead of switched waveforms) and also <span class="blsp-spelling-error" id="SPELLING_ERROR_4">flyback</span> converters. It also <span class="blsp-spelling-corrected" id="SPELLING_ERROR_5">describes</span> methods of measuring output noise.<br /><br />If you are planning to design a high voltage power supply for <span class="blsp-spelling-error" id="SPELLING_ERROR_6">photomultipliers</span> (<span class="blsp-spelling-error" id="SPELLING_ERROR_7">PMT's</span>) or other applications requiring low noise, low power in the range of hundreds of volts, you might want to peruse the <span class="blsp-spelling-error" id="SPELLING_ERROR_8">ap</span> note. It is Linear Technology Application Note 118.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-5334763597476402794?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com2tag:blogger.com,1999:blog-4792522150583038579.post-59608626105028218822008-07-29T15:21:00.000-04:002008-08-29T15:24:13.860-04:00Isolated RS-232 Transceiver<a href="http://www.highvoltageinfo.com/uploaded_images/Analog_Devices_RS-232_transeiver-786814.jpg"><img style="FLOAT: right; MARGIN: 0px 0px 10px 10px; CURSOR: hand" alt="" src="http://www.highvoltageinfo.com/uploaded_images/Analog_Devices_RS-232_transeiver-786797.jpg" border="0" /></a> When there are high voltage circuits, such as in a high voltage power supply, and you need to control them via an RS-232 interface, it is usually a good idea to isolate the computer from the analog electronics. Here is information about a new isolated RS-232 <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">transceiver</span> that may be of interest.<br /><br /><div><a class="byline" name="a080725">Fully Isolated RS-232 Transceiver Readies For Harsh Environments </a><br />Claiming title as the industry’s first fully isolated single-package surface mount RS-232 transceiver with integrated dc/dc converter to supply isolated power, the ADM3251E transceiver integrates a line driver, line receiver, oscillator, rectifier, regulator, voltage doubler, voltage inverter, and transformers into a single chip that isolates both the data and power lines on chip. The transceiver incorporates the company’s <span class="blsp-spelling-error" id="SPELLING_ERROR_1">iCoupler</span> and <span class="blsp-spelling-error" id="SPELLING_ERROR_2">isoPower</span> isolation technologies to enable a 2.5 <span class="blsp-spelling-error" id="SPELLING_ERROR_3">kV</span> isolation rating and it complies with industry-standard isolation regulations including UL1577 and DIN <span class="blsp-spelling-error" id="SPELLING_ERROR_4">VDE</span> 0884-10. Additionally, the ADM3251E comes in a lead-free, 13 mm × 10.56 mm 20-lead <span class="blsp-spelling-error" id="SPELLING_ERROR_5">WSOIC</span> surface-mount package. Price is $2.99 each/1,000. Analog Devices, Inc., <span class="blsp-spelling-error" id="SPELLING_ERROR_6">Norwood</span>, MA. (800) 426-2564.<br /><br /></div><div></div><br /><br /><div></div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-5960862610502821882?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com1tag:blogger.com,1999:blog-4792522150583038579.post-20872480666625881672008-07-24T14:21:00.005-04:002008-07-24T14:48:56.042-04:00New High Voltage Laboratory in IndiaThis week, the M P <span class="blsp-spelling-error" id="SPELLING_ERROR_0">Varshney</span> High Voltage Laboratory was dedicated at the <span class="blsp-spelling-error" id="SPELLING_ERROR_1">Zakir</span> <span class="blsp-spelling-error" id="SPELLING_ERROR_2">Husain</span> College of Engineering and Technology, <span class="blsp-spelling-error" id="SPELLING_ERROR_3">Aligarh</span> Muslim University.<br /><br />Professor (Dr.) M P <span class="blsp-spelling-error" id="SPELLING_ERROR_4">Varshney</span>, an alumnus of this University during 1942-46 has graciously made a large donation for the extension of the High Voltage Laboratory, named after him.<br /><br />It's been said, "The electrical <span class="blsp-spelling-error" id="SPELLING_ERROR_5">department</span> of this college boasts of the best high voltage laboratory in the entire north India.<br /><br />This is but one of several excellent high voltage laboratories in India.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-2087248066662588167?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com1tag:blogger.com,1999:blog-4792522150583038579.post-9429565460444163742008-07-09T11:43:00.000-04:002008-07-09T11:44:18.676-04:00Simple High Voltage Power Supply CircuitThere's a Design Idea in <span class="blsp-spelling-error" id="SPELLING_ERROR_0">EDN</span> magazine that uses just one <span class="blsp-spelling-error" id="SPELLING_ERROR_1">IC</span> in a simple, high voltage power supply. See the June 26, 2008 issue. It's a fixed output supply with limited adjustment capability. If you need a small, inexpensive power supply, this is a good possibility.<br /><br /><br />The output voltage can be increased by adding more secondaries, and stacking them up, as in the design as shown.<br /><br /><br />The regulation is not great, but if that is all you need, then that is <span class="blsp-spelling-error" id="SPELLING_ERROR_2">ok</span>. However, if you prefer better regulation, and if you don't need a floating output, then the circuit would work better if the voltage feedback was taken from the output (with a voltage divider) rather than from a separate secondary winding.<br /><br /><br />You can find the article at <a href="http://www.edn.com/article/CA6571003.html">http://www.edn.com/article/CA6571003.html</a><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-942956546044416374?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-87520443361889623622008-07-01T11:16:00.004-04:002008-07-01T14:01:56.644-04:00Beware of Conterfeit High Voltage Transistors<div><div><div>Apparently, counterfeit high voltage transistors are around. Here's what Geoff found:</div><img style="FLOAT: right; MARGIN: 0px 0px 10px 10px; CURSOR: hand" height="145" alt="" src="http://www.highvoltageinfo.com/uploaded_images/bu505thomchip-750567.jpg" width="278" border="0" /><br /><div>Our design had worked for 20 years in the field, then suddenly last year we had failures. My gut reaction was counterfeiting, even though I had never experienced it before, and this was without even laying a <span class="blsp-spelling-error" id="SPELLING_ERROR_0">CRO</span> probe on the circuit. A month ago, our RF engineer and I looked into it, wondering what was wrong with the design. After a week of bench tests and simulations we went back to basics. We measured the <span class="blsp-spelling-error" id="SPELLING_ERROR_1">VCEO</span> and found the problem! When I etched the metal from some samples, we found a tiny die on the faulty parts. This <span class="blsp-spelling-corrected" id="SPELLING_ERROR_2">occurred</span> with ST BU505's and some <span class="blsp-spelling-error" id="SPELLING_ERROR_3">ON Semiconductor</span> <span class="blsp-spelling-error" id="SPELLING_ERROR_4">MJE</span>8502's, though these are obsolete.</div><br /><div></div><div>It is likely this won’t affect many, but we have good evidence of counterfeit high voltage <a href="http://www.highvoltageinfo.com/uploaded_images/mje8502ver2-702152.jpg"><img style="FLOAT: right; MARGIN: 0px 0px 10px 10px; WIDTH: 148px; CURSOR: hand; HEIGHT: 218px" height="248" alt="" src="http://www.highvoltageinfo.com/uploaded_images/mje8502ver2-702149.jpg" width="197" border="0" /></a>transistors from some suppliers. The types so far affected are BU505 and <span class="blsp-spelling-error" id="SPELLING_ERROR_5">MJE</span>8502. These are 1500V <span class="blsp-spelling-error" id="SPELLING_ERROR_6">VCES</span> and 700V <span class="blsp-spelling-error" id="SPELLING_ERROR_7">VCEO</span>. We noted failures in our products and traced to a very low <span class="blsp-spelling-error" id="SPELLING_ERROR_8">VCEO</span> which I checked with a current limited voltage source. We found ST brand BU505’s failing at slightly more than 500V <span class="blsp-spelling-error" id="SPELLING_ERROR_9">VCEO</span> and the same for ON Semiconductor branded <span class="blsp-spelling-error" id="SPELLING_ERROR_10">MJE</span>8502. I etched a couple of BU505’s with nitric acid to remove all metal. One was a good tested one and one the other a failed one. There was a completely different die size between the two. The good one had a 3.3mm die and the bad one a 1.8mm die. The good one had the markings etched and the bad one had markings printed. These devices are often used for <span class="blsp-spelling-error" id="SPELLING_ERROR_11">switchmode</span> supplies and horizontal drive in CRT’s, where circuit designs may not ever allow the base to be open circuit, i.e., driven from a low impedance source, so I guess that many users many not see the failures.</div><br /><div>I presented the data to St Microelectronics and they confirmed the likelihood of counterfeit <a href="http://www.highvoltageinfo.com/uploaded_images/BU505ver2-744724.jpg"><img style="FLOAT: right; MARGIN: 0px 0px 10px 10px; CURSOR: hand" height="195" alt="" src="http://www.highvoltageinfo.com/uploaded_images/BU505ver2-744722.jpg" width="277" border="0" /></a>devices. Now we will have to do incoming <span class="blsp-spelling-error" id="SPELLING_ERROR_12">VCEO</span> checks of all batches until the situation improves. We try to get these normally from mainstream suppliers, but sometimes supply problems prevent this. It looks like we will have to get smarter with purchasing though. This is the first time I have personally come across this in 20+ years of engineering.</div><br /><br /><br /><br /><div></div><br /><br /><br /><br /><div></div></div></div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-8752044336188962362?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-88449150943851690402008-06-18T13:08:00.003-04:002008-06-20T18:03:34.314-04:00900V TransistorsReal high voltage transistors can be difficult to find. What I mean by "real" is that the transistor has characteristics similar to low voltage transistors, but just have higher operating voltage capability. For example, some <span class="blsp-spelling-error" id="SPELLING_ERROR_0"><span class="blsp-spelling-error" id="SPELLING_ERROR_0">HV</span></span> transistors have very low beta, and very high leakage current, thereby making them unattractive in many applications, particularly low current applications. Thus, the application spectrum is narrowed somewhat.<br /><br /><span class="blsp-spelling-error" id="SPELLING_ERROR_1"><span class="blsp-spelling-error" id="SPELLING_ERROR_1">Infineon's</span></span> <span class="blsp-spelling-error" id="SPELLING_ERROR_2"><span class="blsp-spelling-error" id="SPELLING_ERROR_2">CoolMOS</span></span>™ 900V power <span class="blsp-spelling-error" id="SPELLING_ERROR_3"><span class="blsp-spelling-error" id="SPELLING_ERROR_3">MOSFETs</span></span> are the industry’s first 900 V <span class="blsp-spelling-error" id="SPELLING_ERROR_4"><span class="blsp-spelling-error" id="SPELLING_ERROR_4">superjunction</span></span> <span class="blsp-spelling-error" id="SPELLING_ERROR_5"><span class="blsp-spelling-error" id="SPELLING_ERROR_5">MOSFETs</span></span> specifically intended for high-efficiency applications. For example, quasi-resonant <span class="blsp-spelling-error" id="SPELLING_ERROR_6"><span class="blsp-spelling-error" id="SPELLING_ERROR_6">flyback</span></span> designs for LCD TV power supplies can benefit from a higher <span class="blsp-spelling-error" id="SPELLING_ERROR_7"><span class="blsp-spelling-error" id="SPELLING_ERROR_7">flyback</span></span> voltage, which provides a longer primary duty cycle with reduced peak current, true zero-voltage switching and significantly lower voltage stress on the secondary side. Other applications include crowbar circuits and high voltage switching.<br /><br />Devices with ON resistance of 0.34ohms are available now, and soon to be released are parts with 0.12 ohm ON resistance.<br /><br />As with many high voltage components, it is important to review the data sheets, since there are often limitations not found with their low voltage brethren. For example, in <span class="blsp-spelling-error" id="SPELLING_ERROR_8"><span class="blsp-spelling-error" id="SPELLING_ERROR_8">Infineon</span></span> <span class="blsp-spelling-error" id="SPELLING_ERROR_9"><span class="blsp-spelling-error" id="SPELLING_ERROR_9">IPW</span></span>90 family, drain-source breakdown voltage rating varies significantly with temperature. <span class="blsp-spelling-corrected" id="SPELLING_ERROR_10">While</span> it is 900V at 25C, it goes down to 850V at -20C. Also, drain-source leakage current is just 100<span class="blsp-spelling-error" id="SPELLING_ERROR_10">nA</span>, but it is specified with no D-S voltage applied. If you look at the breakdown spec, it <span class="blsp-spelling-corrected" id="SPELLING_ERROR_11">specifies</span> a maximum of 250 <span class="blsp-spelling-error" id="SPELLING_ERROR_12"><span class="blsp-spelling-error" id="SPELLING_ERROR_11">microamps</span></span> at 900V, however.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-8844915094385169040?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-50352972543924123932008-06-13T17:58:00.001-04:002008-06-13T18:46:51.522-04:00Isolate, Convert, Boost, and Rescale Process SignalsEven when you are not working with high voltage, it is useful to be able to isolate signals by kV.<br /><br />The model <span class="blsp-spelling-error" id="SPELLING_ERROR_0">TEVL</span>-<span class="blsp-spelling-error" id="SPELLING_ERROR_1">HVDC</span> accepts a DC voltage input and provides an optically isolated DC voltage or current output that is linearly related to the input. This module is unique because it is field <span class="blsp-spelling-error" id="SPELLING_ERROR_2">rangeable</span> for voltage inputs from 100 <span class="blsp-spelling-error" id="SPELLING_ERROR_3">VDC</span> to 2000 <span class="blsp-spelling-error" id="SPELLING_ERROR_4">VDC</span>. Typical applications include signal isolation, signal conversion, signal attenuation or a combination of the three.The optical isolation between input and output makes it useful for ground loop elimination, common mode signal rejection or noise pickup reduction. The power supply is isolated, resulting in full 3-way (input, output, power) isolation.<br /><br />The input and output range settings are configured by the factory to customer requirements, but they can be reconfigured in the field via internal switches. Common range settings are on the module label. A user specified range is available that can be factory configured to meet your specific requirements<br /><br /><ul><br /><li>High Voltage Input Ranges from 100 <span class="blsp-spelling-error" id="SPELLING_ERROR_5">VDC</span> to 2000 <span class="blsp-spelling-error" id="SPELLING_ERROR_6">VDC</span> </li><br /><br /><li>High Input Impedance</li><br /><br /><li>2000 V Full Input/Output/Power Isolation </li></ul><br /><br /><p>For more information see <a href="http://www.ferret.com.au/common/clickthrough2.asp?intType=2&strTarget=http%3A%2F%2Fwww%2Eveederline%2Ecom%2Eau&intOrigin=3&strID=239085" target="_blank">http://www.ferret.com.au/common/clickthrough2.asp?intType=2&strTarget=http%3A%2F%2Fwww%2Eveederline%2Ecom%2Eau&intOrigin=3&strID=239085</a></p><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-5035297254392412393?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com1tag:blogger.com,1999:blog-4792522150583038579.post-8424504903914880722008-06-03T18:18:00.002-04:002008-06-03T18:21:21.231-04:00High Voltage Power Supply Selection Issues - Part 2A couple more high <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">voltage</span> issues to consider:<br /><br />Some power supplies require a minimum load to regulate correctly. Particularly at low output current and low output voltage, this is a concern. Thus, after the minimum desired operating conditions are <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">determined</span>, it is worthwhile checking with <span class="blsp-spelling-corrected" id="SPELLING_ERROR_1">the</span> manufacturer to determine if the selected power supply can operate at those conditions.<br /><br />It is also worthwhile investigating power supply operation when the output current reaches the limit. Some power supplies exhibit <span class="blsp-spelling-error" id="SPELLING_ERROR_2"><span class="blsp-spelling-error" id="SPELLING_ERROR_1">foldback</span></span>, while others will limit the current to the max value. When the limiting is precise, then it is termed current regulation. <span class="blsp-spelling-corrected" id="SPELLING_ERROR_3">Some</span> power supplies can operate in current limit mode <span class="blsp-spelling-corrected" id="SPELLING_ERROR_4">indefinitely</span>, while others cannot, and they can overheat or fail.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-842450490391488072?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-56590842451371430242008-05-29T14:37:00.004-04:002008-06-03T18:20:27.171-04:00High Voltage Power Supply Selection IssuesWhen comparing high voltage power supplies from <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">different</span> manufacturers, here are a few issues to look at:<br /><br />Is ripple specified in peak-to-peak or <span class="blsp-spelling-error" id="SPELLING_ERROR_1">rms</span>? For many applications, it is the peak-to-peak that matters. If the ripple is specified as <span class="blsp-spelling-error" id="SPELLING_ERROR_2">rms</span>, it is not as simple as multiplying the <span class="blsp-spelling-error" id="SPELLING_ERROR_3">rms</span> by roughly 3 to get peak-to-peak. Due to switching regulator spikes or high voltage diode issues, the ratio between peak and <span class="blsp-spelling-error" id="SPELLING_ERROR_4">rms</span> may be much higher.<br /><br />Are the monitors derived from separate sources as the feedback control signals? If so, then these independent signals can be used to determine when the power supply is not working correctly. On the contrary, when the same signal is used for both voltage monitor and voltage feedback, it is possible that the power supply output is much lower than the set point, and the monitor will not know.<br /><br />What is the output connector? As high voltage connectors are not standardized, the output connector might even be the deciding factor. Issues include shielded vs. unshielded, the bend radius of the wire, size and cost. Lead time of the mating connector and cable can be substantial, and in some cases it can take longer to get a cable than the power supply.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-5659084245137143024?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-216911373826379062008-05-02T16:35:00.003-04:002008-05-09T17:09:01.398-04:00Plasma SterilizationIn still another use for high voltage, researchers have developed a plasma that operates at room temperature. The plasma is generated between a high voltage probe and the surrounding room air. One use envisioned is to sterilize medical instruments. A second use is to kill bacteria, specifically dental.<br /><br />Generally, plasmas operate at high temperature, and thus are impractical to use on humans. However, these develpments appear promising.<br /><br />The research paper is in <a href="http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000092000015151504000001&idtype=cvips&gifs=yes">Applied Physics Letters</a>.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-21691137382637906?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-12254096153428087222008-04-24T11:18:00.000-04:002008-04-24T14:33:49.897-04:00A Few Low Cost High Voltage Power Supply Circuits<html> <body> Here's a circuit that generates 100V from 25V. Output current is 25mA. You can find it at <a href="http://www.edn.com/index.asp?layout=article&articleid=CA46343"> http://www.edn.com/index.asp?layout=article&articleid=CA46343</a> <br><br> Another high voltage power supply circuit is at <a href="http://www.instructables.com/id/Cheap-Semi-High-Voltage-Power-Supply/"> http://www.instructables.com/id/Cheap-Semi-High-Voltage-Power-Supply/</a> It is actually just a high voltage multiplier circuit, and is open loop. In other words, you put in an ac signal, and you get the high voltage output.<br><br> This is a low cost 50kV power supply. Like the one above, it is open loop, however in this case it includes a way to vary the output voltage. It uses parts that are available at low cost. See <a href="http://www.instructables.com/id/Build-a-Variable-High-Voltage-Power-Supply/"> http://www.instructables.com/id/Build-a-Variable-High-Voltage-Power-Supply/</a> <div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-1225409615342808722?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-14832623566712821472008-04-19T16:19:00.004-04:002008-04-20T08:30:06.262-04:00Alternating Current – Minimum Approach DistanceThe following table is from Occupational Safety & Health Standards Board of the California Cal/OSHA program website. <a href="http://www.dir.ca.gov/oshsb/rubberglove.html">http://www.dir.ca.gov/oshsb/rubberglove.html</a> Please see this website for more information.<br /><br />It is related to conductors and equipment energized over 7,500 volts<br /><br />Alternating Current – Minimum Approach Distance<br /><br /><br /><table border="1"><tbody><tr><th>Normal Voltage Range (Phase to Phase)Kilovolt </th><th>Approach Distance Phase to Ground Exposure </th></tr><tr><td>Above 0.6 to 15</td><td>2 ft 1 in.</td></tr><tr><td>Above 15 to 36</td><td>2 ft. 4 in.</td></tr><tr><td>Above 36 to 46</td><td>2 ft 7 in.</td></tr><tr><td>Above 46 to 72.5</td><td>3 ft 0 in.</td></tr><tr><td>Above 72.5 to 121</td><td>3 ft 4 in.</td></tr><tr><td>Above 121 to 145</td><td>3 ft 7 in.</td></tr><tr><td>Above 145 to 169</td><td>4 ft 0 in.</td></tr><tr><td>Above 169 to 242</td><td>5 ft. 3 in.</td></tr><tr><td>Above 242 to 362</td><td>8 ft 6 in.</td></tr><tr><td>Above 362 to 552</td><td>11 ft. 3in.</td></tr><tr><td>Above 552 to 765</td><td>15 ft 0 in.</td></tr></tbody></table></tbody><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-1483262356671282147?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com1tag:blogger.com,1999:blog-4792522150583038579.post-31679768016741539712008-04-09T14:19:00.000-04:002008-04-09T14:44:29.243-04:00Human Body Resistance and CapacitanceHere is an interesting piece written by Paul E. Schoen of P S Technology, Inc.<br /><br />There is some more information [regarding the resistance of a human body] at <a href="http://van.physics.uiuc.edu/qa/listing.php?id=6793">http://van.physics.uiuc.edu/qa/listing.php?id=6793</a> , where it states that the external human body resistance is about 1k to 100k Ohms, and the internal resistance is 300 to 1000 ohms. Only a thin layer of dry skin separates the internal resistance from an external object.<br /><br />The human body capacitance to a far ground is 100-200 pF, which is really a minimum value. This correlates to an impedance of about 13 megohms at 60 Hz, which corresponds to a minimum of 9 uA at 120 VAC to ground. This is enough to be sensed and used for capacitively operated light dimmers.<br /><br /><br /><br /><br /><br /><br />Here is a way to measure your body capacitance: <a href="http://web.mit.edu/Edgerton/www/Capacitance.html">http://web.mit.edu/Edgerton/www/Capacitance.html</a><br /><br /><br /><br /><br /><br /><br />The inside of your body can be considered a conductor, and thus if you place your hand flat on a metal plate, you will form a capacitor with an area of perhaps 15 square inches, with a thin (maybe 0.005”) insulating layer of dry skin, which will form a capacitor much higher in value than the 200 pF stated above. According to a formula in <a href="http://www.sayedsaad.com/fundmental/11_Capacitance.htm">http://www.sayedsaad.com/fundmental/11_Capacitance.htm</a> , this would be C = 0.2249 * k * A / d = 1350 pF, (assuming k for skin is 2, about like dry paper). This will be an impedance of about 2 megohms , and current of 60 uA. This is still below the normal threshold of sensation, and still far below the usual safe current levels of 1 to 5 mA.<br /><br /><br /><br /><br /><br /><br />The actual thickness of the epidermis (per <a href="http://dermatology.about.com/cs/skinanatomy/a/anatomy.htm">http://dermatology.about.com/cs/skinanatomy/a/anatomy.htm</a> ) varies from 0.05 mm (0.002”) for eyelids to 1.5 mm (0.06”) for palms and soles, but the actual outer layer of the epidermis that is a good insulator is composed of flat, dead cells, which is much thinner. So the capacitance could be much higher than the quick estimate above.<br /><br /><br /><br /><br /><br /><br />Probably the main reason for electrical current to reach levels high enough for electrocution to occur (6 to 200 mA for 3 seconds, according to <a href="http://www.codecheck.com/ecution.htm">http://www.codecheck.com/ecution.htm</a> ), is when skin becomes sweaty or otherwise loses its dry protective layer, which quickly exposes the underlying 1000 ohms or less, which will conduct 120 mA at 120 VAC.<br /><br /><br /><br /><br /><br /><br />There are safe ways to measure the body’s resistance and capacitance using realistic higher voltages, skin conditions, and contact surfaces, but I’m not going to suggest anyone try it. Suffice it to say that ohmmeter readings are misleading, and any carelessness around any kind of voltage source can be dangerous.<br /><br /><br /><br /><br /><br /><br />For very high voltages, there are standard minimum distances that must be maintained between a worker and an energized line: <a href="http://www.dir.ca.gov/oshsb/rubberglove.html">http://www.dir.ca.gov/oshsb/rubberglove.html</a> . I found this on a search for rubber glove testing.<br /><br /><br /><br /><br /><br /><br />The field intensity near high voltage lines is so great that it might be fatal to touch them even if you were suspended in free air. You may notice that birds can sit on lower voltage transmission lines which are 5kV to 50 kV or so, but not on 200kV+ lines.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-3167976801674153971?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com31tag:blogger.com,1999:blog-4792522150583038579.post-14107066520526014442008-04-02T08:59:00.006-04:002008-04-04T11:15:43.839-04:00Extremely low cost high voltage power suppliesIf you are looking for an extremely low cost high voltage power supply, a good place to look is consumer products that <span class="blsp-spelling-corrected" id="SPELLING_ERROR_0">incorporate</span> high voltage. For example there are electronic fly swatters that claim to produce 4<span class="blsp-spelling-error" id="SPELLING_ERROR_1">kV</span>! Of course the current is very low, and performance in terms of ripple, regulation and stability is not all that good. The electronic fly swatter may not even put out nearly the voltage claimed. However, if these performance related issues are not important in your application, or just need to generate a spark, you're in luck. Besides, you can find them for under $10, and sometimes even under $5. Other products to consider as a source of low cost high voltage are air purifiers, mosquito zappers, LCD display backlights, piezoelectric spark generators, and vehicle electronic ignitions.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-1410706652052601444?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-9414255297932627192008-03-27T16:38:00.001-04:002008-03-27T17:07:53.789-04:00Welcome Package for Opto IsolatorsNew high voltage <span class="blsp-spelling-error" id="SPELLING_ERROR_0">opto</span> isolators are always a welcome addition to a designers. <span class="blsp-spelling-error" id="SPELLING_ERROR_1">Optek</span> has a new configuration that you may find handy.<br /><br />They have axial fiber optic isolators offered in isolation distances from 18mm to 80mm. Providing power electronics engineers with a means to isolate high voltage input/output circuits over varying distances, <span class="blsp-spelling-error" id="SPELLING_ERROR_2">TT</span> electronics <span class="blsp-spelling-error" id="SPELLING_ERROR_3">OPTEK</span> Technology has developed a series of axial optical isolators using plastic optical fiber. Designated the <span class="blsp-spelling-error" id="SPELLING_ERROR_4">OPI</span>1270 Series axial fiber optic isolators, the devices are constructed using a visible red LED emitter and a <span class="blsp-spelling-error" id="SPELLING_ERROR_5">phototransistor</span> detector in separate opaque molded plastic modules, linked by a shrouded optical cable that shields the optical signal from dust and other <span class="blsp-spelling-error" id="SPELLING_ERROR_6">contaminations</span>.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-941425529793262719?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com1tag:blogger.com,1999:blog-4792522150583038579.post-48807186170657650852008-03-21T16:37:00.002-04:002008-03-21T16:44:00.642-04:00High Voltage CommentsYou may noticed a recent change in our high voltage blog. You now have an opportunity to leave a comment on any of the posts. Feel free to indicate what you like/dislike, what you agree/disagree with, or you may submit ideas for future posts. Questions are always welcomed. Of course we expect all comments to be in keeping with the professional nature of the blog. <br /><br />We look forward to your comments!<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-4880718617065765085?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com1tag:blogger.com,1999:blog-4792522150583038579.post-38269073006010563142008-03-14T11:43:00.002-04:002008-03-14T11:48:09.680-04:00High Voltage in the NewsParts were recently stolen from towers carrying 115kV wires. The thieves took hundreds of steel struts, nuts and bolts from three 115kV high voltage towers in Thailand. The 130 foot high towers leaned much more than normal during a windy evening, causing an investigation. The parts were probably taken in order to sell them as scrap metal.<br /><br />Imagine what would have happened if the towers fell down!<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-3826907300601056314?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0tag:blogger.com,1999:blog-4792522150583038579.post-22930792992875424072008-03-03T11:30:00.000-05:002008-03-03T20:43:24.228-05:00High Voltage Chip ResistorsIt's often tough to find good resistors with high enough voltage and resistance ratings. Stackpole has expanded its HVC product line in both areas. Their surface mount resistors are now available up to 10Gohms, and with voltage ratings up to 25kV.<br /><br />Stackpole claims that their manufacturing process yields resistors with lower noise and better stability.<br /><br /><br />Other specifications include:<br /><ul><li>Temperature coefficient ratings are as low as 25 ppm per degree C. </li><br /><li>Tolerance as low as 0.5%</li><br /><li>Voltage ratings from 5kV to 25kV for chip sizes 0603 to 2512, respectively.</li></ul><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/4792522150583038579-2293079299287542407?l=www.highvoltageinfo.com%2Fhigh-voltage-blog.html' alt='' /></div>Fred Wrighthttp://www.blogger.com/profile/07850278226396218162noreply@blogger.com0