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
There is no suggestion in the specifications for the 34401A that the
accuracy suffers by selecting 10G ohm input resistance on the .1 to 10V
range so why would they make 10M ohm the default? I can think of very
few cases where having the 10M ohm i/p resistor switched in is better
for accuracy
] 34401A Why 10M ohm default i/p resistance?
There is no suggestion in the specifications for the 34401A that the
accuracy suffers by selecting 10G ohm input resistance on the .1 to 10V
range so why would they make 10M ohm the default? I can think of very few
cases where having the 10M ohm i/p
In message 5346a952.9080...@toneh.demon.co.uk, Tony writes:
There is no suggestion in the specifications for the 34401A that the
accuracy suffers by selecting 10G ohm input resistance on the .1 to 10V
range so why would they make 10M ohm the default?
In addition to the compatibility reasons
It is more along the lines of building a voltage divider with stable
resistors. A !G ohm voltage divider would be more expensive to build with
the same stability that you can get from 10M ohms. There are trade offs in
all designs. The cost benefit ratio just is not there. If you really need
high
. Many of the accurate ones want to see a 10 meg input.
Also, some meters change input impedance depending on the selected range.
T
- Original Message - From: Tony vn...@toneh.demon.co.uk
To: volt-nuts@febo.com
Sent: Thursday, April 10, 2014 10:23 AM
Subject: [volt-nuts] 34401A Why 10M ohm
so why do you care what the input is as long as you know what it is and how
to make it do what you want?
On Thu, Apr 10, 2014 at 1:16 PM, Brent Gordon volt-n...@adobe-labs.comwrote:
Pure conjecture: So that the reading on the 34401A matches that on a $20
DVM.
Or stated differently: So
Very unlikely I'd have thought - the relay (K104) which selects between
the high and low voltage ranges also selects the I/P resistance. It
wouldn't get used any more than the identical relay |(K102) which
switches when changing between 10 and 100V ranges.
In any case a typical signal relay
Hi John:
Because when measuring a source with a high resistance you get a different
answer.
Some W.W.II electronics specified 1 kOhm/Volt meters and if you used a VTVM you
got the wrong results.
If a test procedure specifies a 10MOhm input meter and you use a higher input Z
then you may get
With the 1K ohm per volt you need to know what range you are using. You do
have to know your meter and know how to correct for loading or not loading.
It is not very practical to have a bunch of different input standards 10M
works for a lot of things and is the the standard voltage divider.
On
Gordon wrote:
Pure conjecture: So that the reading on the 34401A matches that on a
$20 DVM.
I assume you mean when the DVM is disconnected - otherwise you wouldn't
spend more than $20 on a meter! But I said that in my original post:
/So why would they do this? Could it be
: Thursday, April 10, 2014 4:16 PM
Subject: Re: [volt-nuts] 34401A Why 10M ohm default i/p resistance?
Pure conjecture: So that the reading on the 34401A matches that on a $20
DVM.
Or stated differently: So that the input impedance is the same as other
DVMs.
Brent
On 4/10/2014 8:23 AM, Tony
On 4/10/2014 3:18 PM, Tony wrote:
Gordon wrote:
Pure conjecture: So that the reading on the 34401A matches that on a
$20 DVM.
I assume you mean when the DVM is disconnected - otherwise you
wouldn't spend more than $20 on a meter! But I said that in my
original post:
Actually, I meant
Only specialized meters can provide virtually infinite input R at
voltages above the 10 to 20 V or so native range of conventional
amplifiers, so you have to use some kind of attenuator to cover the
higher ranges anyway. 10 megs and 1 meg (and sometimes 11) are the
traditional values used,
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