[volt-nuts] 34401A Why 10M ohm default i/p resistance?

2014-04-11 Thread frank . stellmach
Hello   In the manual (!), HP reasons the 10M standard input resistance:   "Normally, the multimeter’s input resistance is fixed at 10 MΩ for all dc voltage ranges to minimize noise pickup."   I explained that to myself like this: AC stray fields or noisy high impedance sources induce noise input

Re: [volt-nuts] 34401A Why 10M ohm default i/p resistance?

2014-04-11 Thread Tony
Hi, On 11/04/2014 10:53, frank.stellm...@freenet.de wrote: Hello In the manual (!), HP reasons the 10M standard input resistance: "Normally, the multimeter’s input resistance is fixed at 10 MΩ for all dc voltage ranges to minimize noise pickup." Oops! I'm ashamed to say I missed that!

Re: [volt-nuts] 34401A Why 10M ohm default i/p resistance?

2014-04-11 Thread Poul-Henning Kamp
In message <53482d9e.9060...@toneh.demon.co.uk>, Tony writes: > I did find this explanation in the 3458A manual: > > When making DC voltage measurements, you can fix the multimeter's input > resistance using the FlXEDZ command. This is useful to prevent a change > in input resistance caused by

Re: [volt-nuts] 34401A Why 10M ohm default i/p resistance?

2014-04-11 Thread WarrenS
"You can't have your cake and eat it!" well said Too true, that the 10 MΩ reduces the noise pickup, but **only** when the DVM input is **open circuited**, which is not so good for measuring anything if the signal is not connected. Otherwise the noise pickup is a function of the impedance of

Re: [volt-nuts] 34401A Why 10M ohm default i/p resistance?

2014-04-11 Thread Tony
Hi Paul, On 11/04/2014 19:18, Poul-Henning Kamp wrote: In message <53482d9e.9060...@toneh.demon.co.uk>, Tony writes: I did find this explanation in the 3458A manual: When making DC voltage measurements, you can fix the multimeter's input resistance using the FlXEDZ command. This is useful to

Re: [volt-nuts] 34401A Why 10M ohm default i/p resistance?

2014-04-11 Thread Poul-Henning Kamp
In message <534840da.4070...@toneh.demon.co.uk>, Tony writes: >> Many of the attributes of the input circuit are not there for >> voltage metrology. >> >I can't think of any - I'd be interested to know what you have in mind? One of the articles in HP Journal is specifically about how the input ci

Re: [volt-nuts] 34401A Why 10M ohm default i/p resistance?

2014-04-11 Thread Tony
On 11/04/2014 20:59, Poul-Henning Kamp wrote: In message <534840da.4070...@toneh.demon.co.uk>, Tony writes: Many of the attributes of the input circuit are not there for voltage metrology. I can't think of any - I'd be interested to know what you have in mind? One of the articles in HP Journ