I am probably missing an obvious point. If the CTL has addressed 2.1.1.7 and said that the requirement simply is >100 Mohm || <25 pF, why are we going through this special probe construction/evaluation stuff and not just buy an OTS probe that meets this (I see a Tek and HP probe that will work)?
Another question - will the probe be subject to ISO17025 calibration? Brian > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf Of > [email protected] > Sent: Wednesday, May 11, 2011 4:41 PM > To: 'John Woodgate'; [email protected] > Subject: RE: UL/60950-1 Cl. 2.1.1.7 Probe > > Hi John: > > > When conducting the voltage decay measurement, the measurement > > is either made with, or referred to, an instrument having an input > > impedance consisting of a resistance of 100 Mohms ± 5 Mohms > > in parallel > > with an input capacitance of 25 pF or less. > > Agreed. > > > So any 100: 1 probe can probably be used. I would expect the > > capacitance > > of a 100:1 probe to be much less than 15 pF, so just add > extra shunt > > capacitance to taste. > > Be aware that not all 100:1 probes have a 100 Mohm > input resistance. The 100 Mohm input resistance is > critical to the correct measurement. > > The capacitance is of no consequence since the measurement > only applies if the capacitance is 0.1 uF or more. Probe > capacitances are in the range of 2 to 20 pF and are > negligible when in parallel with 0.1 uF. See my "Technically > Speaking" column in Volume 4, Number 4, December 2008, > issue of IEEE PSES "The Product Safety Engineering > Newsletter." > > This is available to IEEE PSES members at: > > http://ewh.ieee.org/soc/pses/society/08V4N4.pdf > > > Best regards, > Rich - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
