Best way to measure the waveform of a 200us 800V 1500A DC Pulsed supply - Page 1
Forum section: electronics / beginners

author: Houseman
author_rank: Regular Contributor
timestamp: July 23, 2020, 12:07:33 am
content: Hi forum.I need some help for a particular measurement and would also like to learn some theory behind the choice.During Supersonic Cluster Beam Deposition process the plasma is produced by firing argon by a 200us 800V - 1500A DC pulsed waveform at 3 or 5 Hz rate.The arc in vacuum is between the chassis of the machine and a titanium rod that is connected to the cathode of the power supply.Actually the R&D engineer uses an oscilloscope with CH1 attached to a simple AC current probe clamped around one cable (the positive one)The probe is from Chauvin Arnoux Mini-09 used mostly in 50Hz mains monitoring environment:Bandwidth is 48-500Hz.Sensitivity is 100mV DC / A ACApart from the questionable choice of that probe (how can a AC probe of maximum 500Hz bandwidth see such a waveform is a miracle - but it sees it) I think the waveform we observe on the scope must be different from the real one.What sort of probe can I use to see the clear waveform?RF current probe with bandwidth up to 30Mhz?A differential voltage probe? (800VDC??)Thank You

author: langwadt
author_rank: Super Contributor
timestamp: July 23, 2020, 12:14:29 am
content: https://www.keysight.com/en/pd-2877519-pn-N7040A/rogowski-ac-current-probe-23-mhz-3000-a?nid=-32553.1229528.00&cc=DE&lc=ger?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 23, 2020, 12:47:01 am
content: Pearson clamp probe, or Rogowski as above, both excellent options.Voltage yeah, a differential probe with modest bandwidth (mind, many of them roll off at a few MHz so you may miss the edges with a slow one) should do, and saves the trouble of dealing with (modest) ground offsets. Which are probably not the most friendly with that kind of current around.Hmm, that thing must have a satisfying ping or pop when it goes off.Tim

author: David Hess
author_rank: Super Contributor
timestamp: July 23, 2020, 11:45:26 pm
content: My first choice for the voltage measurement would be a Tektronix P6013 or P6015 high voltage probe. Since the voltage is referenced to the chassis, wouldn't a single ended measurement work? If not, two of these probes can be used with two channels to make a differential measurement after some careful calibration and provisions to keep the probes and instrument hidden from those would would borrow them. Personally I would plug them into a 7A13 (100MHz 3.5ns) or 7A22 (1 MHz 350ns) differential vertical amplifier because I have several but I do not advocate that anybody invest in such. If the later is fast enough, then an AM502 differential amplifier could be used with any instrument, but again I do not really recommend this unless you already have one.Tektronix made some high current and fast current clamps; the trick will be avoiding saturation at such a high peak current. The CT-5 is rated to 50 kiloamps peak with a 17.5 nanosecond rise time and 3000 volts clamped to a bare wire. They seem to be available on Ebay for reasonable prices but remember that a suitable current probe must still be attached.