"NOISE data" without the upper and lower Bandwidth used, is a near meaningless number. Doing a ADEV plot of the voltage noise is one nice way to include the Bandwidth with the data. ws **************** I measured a 731 with a scope to see the noise. It was around 25 uVpp. I think that is the most easy way. You see how much disconnected and how much its connected. I úse a tektronix 547 with E-plugin for this. ( a lot cheaper then a 7,5 digit or more multimeter ;-) Fred PA4TIM ***************** Op 27 sep. 2011 om 05:04 heeft "gbusg" <gbusg at comcast.net> het volgende geschreven: > Hi Joe, > > My calculations agree with yours, as far as Fluke specs for your two > voltages are concerned. > > Fluke spec'd Ripple and Noise (all frequencies) as <20 uV rms on the 10V > range. So that would be another 2ppm rms adder for 10Vdc setting, 20ppm > rms > adder for 1Vdc setting and 200ppm rms adder for 100mVdc setting. But I'm > not > immediately sure how that rms noise spec might translate to observed > racking-around on your 3478A (depending on integration time setting on > your > 3478A, etc.). > > Fluke's basic 10 uV adder (for 10Vdc range) translates to 1ppm adder at > 10Vdc setting, 10ppm adder at 1Vdc setting and 100ppm adder at 100mVdc > setting. The way I look at it, that 10 uV adder accounts for some > short-term > instability (which might also show up as some racking around on your > 3478A) > plus DC zero offset (as observed on your 3478A). > > Anyway, obviously the 335D "likes" full (or near full) scale the best. > > You could test your 3478A short-term noise (racking around of readings) by > using it to read a source that's known to be very quiet. Or at least you > could build a 10 to 1 or 100 to 1 resistive divider between 335D and your > 3478A to see if that reduces the observed noise. > > Best, > Greg >

Fluke didn't state the bandwidth for their "Ripple and Noise" spec in the "Specifications" section of their manual for 335D. However in the Performance Test section of their 335D manual, for that test they use a Fluke 931B RMS meter, preceded by a preamplifier having a gain of 1000 and bandpass of 20 Hz to 30 kHz. So I think they "forgot" to state the noise bandwidth on their spec page, even though they intended it. -Greg ----- Original Message ----- From: "WarrenS" <warrensjmail-one@yahoo.com> To: <volt-nuts@febo.com> Sent: Tuesday, September 27, 2011 8:41 AM Subject: Re: [volt-nuts] Fluke 335A "NOISE data" without the upper and lower Bandwidth used, is a near meaningless number. Doing a ADEV plot of the voltage noise is one nice way to include the Bandwidth with the data. ws **************** I measured a 731 with a scope to see the noise. It was around 25 uVpp. I think that is the most easy way. You see how much disconnected and how much its connected. I úse a tektronix 547 with E-plugin for this. ( a lot cheaper then a 7,5 digit or more multimeter ;-) Fred PA4TIM *****************