Thanks for comments, Scott, Robert -- I should clarify. I was referring to reed relays, which are what I use in most of my low-frequency automated test equipment. There may be some plating materials on the contacts, but since they're embedded in a glass capsule, I believe the base material is Kovar.
Coto relay is one mfr. that offers a coaxial configuration for a miniature reed relay geared towards automated test using some nickel/iron allow for the base material for the contacts. Sorry if I've muddied the issue -- hope that helps. Timothy J. Christman Test Engineer Tel 651.582.3141 Fax 651.582.7599 -----Original Message----- From: Scott Lacey [mailto:sco...@world.std.com] Sent: Saturday, May 25, 2002 11:00 AM To: Christman, Timothy (STP) Cc: emc-p...@majordomo.ieee.org Subject: RE: Coaxial Switches - use with spectrum analyzer and gear? Timothy, I'm somewhat sceptical that kovar (nickel/cobalt/iron) would be used for relay contacts. In my experience better quality relays and switches use coin silver or similar for contacts due to it's low resistance. Only the plunger of the relay needs to be of ferrous metal. As to the original question I see no reason why high-quality coaxial switches could not be used as long as they were periodically checked (characterized) the same as all cables and other pieces should be when used for serious work. Scott Lacey On 24 May 2002 at 15:52, Christman, Timothy (STP) wrote: > > This may not be the effect being referred to, but... > > Relays require a ferromagnetic alloy, such as Kovar for the contacts. The > leads leading to the connector are more likely beryllium copper or some > similar material. The weld or joint between them forms a thermoelectrically > active junction, and an associated error potential. > > Ideally, the two contacts form two sets of junctions that are opposite in > polarity. In reality, they are seldom identically constructed, and if > there's a temperature gradient across the part the error is magnified. > Perhaps this was an effort to stress that the signal amplitude should be in > excess of the thermoelectric offsets. > > Another possibility -- Many small form-factor relays are the reed type, so > wiping action across the contacts forms a conduction path. There may be a > minute oxide layer there or elsewhere in the system which will create the > non-linear behavior described. Point contact rectification and dielectric > breakdown become possibilities. > > Probably not pertinent, but interesting. > > Timothy J. Christman > Test Engineer > Tel 651.582.3141 Fax 651.582.7599 > timothy.christ...@guidant.com > Guidant Corporation > 4100 Hamline Ave. N. > St. Paul, MN 55112 USA > www.guidant.com > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
