Paul, There will always be some small current flowing during a hipot test. If there isn't any current flowing, it's probably because you're circuit is open somewhere (probably the test jig, or the hipot tester's leads). To prevent this problem from going undetected some manufacturers began to include an adjustable "minimum current detection" circuit. An alarm sounds if the set minimum current is not detected while the equipment is in test mode. I think QuadTech and Kikusui both sell equipment with "minimum current detection".
A nice feature, but I sometimes wonder how reliable it is. If this is manufacturing's only reason for purchasing a new hipot tester, you might suggest that they just buy a calibrated resistor. Before performing the hipot test, check the hipot tester using the resistor. That way you can be check both the voltage across the test points, and the correct function of the current monitor in the hipot tester. Additionally, if you check the hipot equipment before each equipment test you can justify longer periods between hipot calibrations. This can save you quite a bit of pocket change. A good resistor has high reliability and can calibrated much more cheaply. This isn't too practical for high volume production line testing, but can work pretty well for some machinery manufacturers. Even if you are doing high volume, you can still reasonably use this approach by testing at the beginning and at the end of a lot (kind of a drag if you have a problem with the last unit though). Matt > > Folks, > > My manufacturing contacts have asked for a lead on a supplier of test > equipment that I can use to be able to test the Hi pot lead for it not to > be open. If you run the Hi Pot test holding the lead in the air it will > pass . We need a way to test that the lead is not open . > > The Test requirement (as far as I know) is to verify functionality of the > equipment before testing. > > Best Regards, > > Paul J. Smith, Teradyne > > > > > > > > > Kevin Harris <harr...@dscltd.com> on 09/25/2000 01:39:29 PM > > Please respond to Kevin Harris <harr...@dscltd.com> > > > > > > > > > To: "'Maxwell, Chris'" <chr...@gnlp.com> > > cc: "EMC-PSTC (E-mail)" <emc-p...@ieee.org>(bcc: Paul J > Smith/Bos/Teradyne) > > > > Subject: RE: Battery Safety > > > > > > > > > > Hi, > > I've seen this done before on low current designs. Sometimes when you > replace the batteries in this type of design the circuit voltage does not > have time to drop completely away due to the charge saved on bulk > capacitors. When the new batteries are added the circuit comes up in a > peculiar state. This is particularly true of uP power on reset circuits. > There are more elegant ways to take care of this problem but I suppose a > single resistor would be the cheapest (if one ignored battery life). > > Regards, > > Kevin Harris > Manager, Approval Services > Digital Security Controls > > > > -----Original Message----- > From: Maxwell, Chris [mailto:chr...@gnlp.com] > Sent: Monday, September 25, 2000 11:31 AM > To: 'EMC-PSTC Internet Forum' > Subject: Battery Safety > > > > All, > > We have inherited a design from a company which we purchased. The product > is a handheld and can be operated from a pair of Alkaline batteries. > Inside > the unit, there is a 91 KOhm resistor across the + and - terminals of the > batteries. Since the people who designed the instrument are long gone, > some > of my collegues have asked me if this resistor could be a safety feature. > > I can't think of any way this resistor would help the safety of the > instrument. I did read through the safety test report; and I found no > reference to this resistor being required. All it does is provide a > constant drain on the battery (reducing battery life). It has been > suggested to me that some designers put resistors across batteries to > reduce > the electrical noise in a product. To me a capacitor would be better for > this because it wouldn't drain the battery while it was filtering. Even > so, > isn't a battery the ultimate capacitor? I'm just drawing a blank why > anyone > would do this. I'd love to recommend that we pull this resistor out > because > it's a pain to solder and it affects battery life. However, I don't want > to > sacrifice the safety of the product. > > Anybody want to take a guess at this one? > > Thanks. > > Chris Maxwell, Design Engineer > GN Nettest Optical Division > 6 Rhoads Drive, Building 4 > Utica, NY 13502 > PH: 315-797-4449 > FAX: 315-797-8024 > EMAIL: chr...@gnlp.com > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > 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: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > 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: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > > > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > 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: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
