Sorry I should have said "uv" where ever I said "mv". Too early in the morning where I live in the world.
Bill ----- Original Message ----- From: "Bill Gold" <[email protected]> To: "Discussion of precise voltage measurement" <[email protected]> Sent: Thursday, September 25, 2014 8:10 AM Subject: Re: [volt-nuts] 845ab Led Mod Update > Dallas: > > I check my 845ab yesterday, S/N 4470002. It still has the neon > bulbs/photo resistors chopper. > > From what I can observe the Peak to Peak noise on the 1 mv range is > about +/- 0.1 mv, or a total of around 0.2 mv. As far as temperature drift > I don't know. Never tried to measure that parameter. > > Sure would love to know if the FLUKE modification to the 845ab made in > 1993, when the new circuit was put into production, makes the noise lower. > Or better, if your efforts can make the noise lower on the 1 mv range. > > Bill > ----- Original Message ----- > From: "Dallas Smith" <[email protected]> > To: "Discussion of precise voltage measurement" <[email protected]> > Sent: Wednesday, September 24, 2014 12:06 PM > Subject: [volt-nuts] 845ab Led Mod Update > > > > Well I finally got the 615nm Led's installed and the results seem so so. > > The zero drifted was significantly on the 1uV range. So I used two > > LT1634 1.25 Volt references with the current set by two 43k resistors > > from the ±15 volt supplies. The previous reference used came from the > > -0.4 volts at TP1 and +0.6 volts at TP8. Removed the 150k resistor at > > the positive end of the zero control and lifted the negative end from > > the circuit board the connected the ±1.25 ref to the zero pot. Much > > better stability, drifts by noise about ±.1 to ±.2uv now on 1uv range. > > Is this normal now? Never used a new Fluke 845ab before. The white led's > > seemed to filter the noise better with its persistent, may go back. The > > zero seems stable with ±2 F change in room temperature now. > > _______________________________________________ > > 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. _______________________________________________ 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.
