HP-3458A Zero Reading
I shorted the input terminals of my HP-3458A with a short lead of copper
wire, Bell telephone wire as recommended in the manual. The reading I get
is around 000.00070 mV, or 0.7 uV with NLPC set to 100. I was trying to
evaluate it's use as a null meter for my Fluke 752A divider. This seems a
little higher than I would expect but no amount of running AUTOCAL or ZERO
changes this amount. Is this considered acceptable?
Randy AE6YG
Randy:
I sure hope you are not trying to use 26 ga. telephone wire for the zero
shorting wire. The manual recommends either 14 ga. or 12 ga. solid copper
wire, this is the kind you can get for basic electrical wiring in conduit in
homes, at least in the US. Generically called "TW" in electrician's
language.
My 3458A reads about -0.20 uv before AutoCal and less than +0.20 uv
after, with the short as described in the manual. You will observe that
the HP/Agilent/Keysight manual for the 3458A does not give any "zero"
stability specs, at least that I can find.
I have been using the 3458A for nulling my 752A and have had no problems
with my homemade "low thermal" leads as I described them to you.
Belden/Pomona components. I use 100PLC.
There is an application note from Fluke, I think, on using DVMs for null
meters.
"Fluke_-_Using_a_DMM_to_balance_752A_Divider.pdf " is the name if it.
I think it came from the Fluke
Calibration Website.
Bill
----- Original Message -----
From: "Randy Evans" randyevans2688@gmail.com
To: volt-nuts@febo.com
Sent: Sunday, July 26, 2015 6:19 PM
Subject: [volt-nuts] HP-3458A Zero Reading
I shorted the input terminals of my HP-3458A with a short lead of copper
wire, Bell telephone wire as recommended in the manual. The reading I get
is around 000.00070 mV, or 0.7 uV with NLPC set to 100. I was trying to
evaluate it's use as a null meter for my Fluke 752A divider. This seems a
little higher than I would expect but no amount of running AUTOCAL or ZERO
changes this amount. Is this considered acceptable?
Randy AE6YG
volt-nuts mailing list -- volt-nuts@febo.com
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and follow the instructions there.
On 7/27/2015 7:54 PM, Bill Gold wrote:
You will observe that the HP/Agilent/Keysight manual for the 3458A
does not give any "zero" stability specs, at least that I can find.
On DC 100 mV range, the standard model is spec'd for 14+3 ppm of range @
2 years from calibration, not considering temperature. That's 1.7 uV,
from my reckoning. The OP's reading of 0.7 uV is well within that - it
even beats the 90 day spec.
Bill wrote -
There is an application note from Fluke, I think, on using DVMs for null
meters.
"Fluke_-_Using_a_DMM_to_balance_752A_Divider.pdf " is the name if it.
I think it came from the Fluke Calibration Website.
It is available at
http://www.ko4bb.com/manuals/download.php?file=Fluke/Fluke_-_Using_a_DMM_to_balance_752A_Divider.pdf
John K1AE
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Bill Gold
Sent: Monday, July 27, 2015 7:54 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] HP-3458A Zero Reading
Randy:
I sure hope you are not trying to use 26 ga. telephone wire for the zero
shorting wire. The manual recommends either 14 ga. or 12 ga. solid copper
wire, this is the kind you can get for basic electrical wiring in conduit in
homes, at least in the US. Generically called "TW" in electrician's
language.
My 3458A reads about -0.20 uv before AutoCal and less than +0.20 uv
after, with the short as described in the manual. You will observe that
the HP/Agilent/Keysight manual for the 3458A does not give any "zero"
stability specs, at least that I can find.
I have been using the 3458A for nulling my 752A and have had no problems
with my homemade "low thermal" leads as I described them to you.
Belden/Pomona components. I use 100PLC.
There is an application note from Fluke, I think, on using DVMs for null
meters.
"Fluke_-_Using_a_DMM_to_balance_752A_Divider.pdf " is the name if it.
I think it came from the Fluke
Calibration Website.
Bill
----- Original Message -----
From: "Randy Evans" randyevans2688@gmail.com
To: volt-nuts@febo.com
Sent: Sunday, July 26, 2015 6:19 PM
Subject: [volt-nuts] HP-3458A Zero Reading
I shorted the input terminals of my HP-3458A with a short lead of copper
wire, Bell telephone wire as recommended in the manual. The reading I get
is around 000.00070 mV, or 0.7 uV with NLPC set to 100. I was trying to
evaluate it's use as a null meter for my Fluke 752A divider. This seems a
little higher than I would expect but no amount of running AUTOCAL or ZERO
changes this amount. Is this considered acceptable?
Randy AE6YG
volt-nuts mailing list -- volt-nuts@febo.com
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and follow the instructions there.
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On 7/27/2015 10:26 PM, Mike S wrote:
On 7/27/2015 7:54 PM, Bill Gold wrote:
You will observe that the HP/Agilent/Keysight manual for the 3458A
does not give any "zero" stability specs, at least that I can find.
On DC 100 mV range, the standard model is spec'd for 14+3 ppm of range @
2 years from calibration, not considering temperature. That's 1.7 uV,
from my reckoning. The OP's reading of 0.7 uV is well within that - it
even beats the 90 day spec.
Doh. That 14+3 actually equates to ~=3 ppm ~= 0.3 uV (since reading is
essentially zero), but there's also temperature, which contributes >
0.115 / C.