---------------------------------------- > Date: Sun, 29 Dec 2013 21:44:03 +0100 > From: [email protected] > To: [email protected] > Subject: [volt-nuts] Fluke 845 Modification > > The Fluke 845 is famous for its high resistance measurements, due to the > differential principle. > But its leakage or bias current is not specified at all! > Anyhow, one has to pay a premium price for this ancient technology, > perhaps having bad neon bulbs. > > Well, all those new Super-Zero ChopAmps nowadays are specified for a > typical Ibias @ RT only, like the LTC2054, or the MAX4238/4239. There's > obviously no upper limit testing, and a specified 150pA max over 85°C > temperature range is much too much! > > Therefore I would opt for the ICL7650, guaranteed / tested 10pA max @ > 25°C, with slightly higher noise. > This OpAmp is still available from MAXIM, and from Intersil, again.
With the rise in leakage vs temperature, if 65C operation is important the 7650 is not for you. I think the 85C leakage will be similar to the 4238 > > Frank > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
