3458A resistance calibration
Re To: *Electronics and Books
Dear Frans,
I cant't believe this! Thanks alot!
As you mentioned the VHP101 as a reference resistor in your'98 unit, I
just opened my HP3458A from 2000, and it's also a VHP101!
According to the actual Vishay PG datasheet, it's really the best type
they offer currently.
As I learnt from a Vishay representative years ago, they pair two
resistor elements inside, i.e. a C-foil, and a K-foil, to compensate for
the T.C.
The VHP101 has 10ppm absolute/max. variation over 15..45°C, i.e. an
average of 0.3ppm/K, and it's oil filled, giving 2ppm/6year stability.
Both parameters I really can believe in, (I'm otherwise very sceptical
about Vishays specs) as these are specified as being max. value by this
window definition, and the annual stability of oil filled, hermetically
sealed Vishay types, I have checked on 5 EA VHP202Z over > 5 years,
meanwhile.
I was not aware of this ultra stable reference resistor inside my
instrument, as the 40k resistor in my unit was bent backwards, so I
could not read the type designator, and did not dare to touch it, up to now!
The old CLIP specifies this resistor as having 1.3ppm/K, so I always
assumed a Vishay k-foil of the 1989 era, non oil filled type.
Also the datsheet specified 1ppm/K (selected component), and 10ppm/year,
which also indicated the same type of hermetically sealed Vishay BMF.
So, this is a big surprise, no reason any more to change this reference
resistor.
HP did not change the specification, but the T.C. should be < 0.5ppm/K,
and <1ppm/yr for the Ohm ranges.
Frank
*
Dear Frank,
Could You give me more detail which resistor has C-foil and which K-foil.
Anton
Pada Jumat, 22 Mei 2015 5:44, Frank Stellmach <frank.stellmach@freenet.de> menulis:
Re To: *Electronics and Books
Dear Frans,
I cant't believe this! Thanks alot!
As you mentioned the VHP101 as a reference resistor in your'98 unit, I
just opened my HP3458A from 2000, and it's also a VHP101!
According to the actual Vishay PG datasheet, it's really the best type
they offer currently.
As I learnt from a Vishay representative years ago, they pair two
resistor elements inside, i.e. a C-foil, and a K-foil, to compensate for
the T.C.
The VHP101 has 10ppm absolute/max. variation over 15..45°C, i.e. an
average of 0.3ppm/K, and it's oil filled, giving 2ppm/6year stability.
Both parameters I really can believe in, (I'm otherwise very sceptical
about Vishays specs) as these are specified as being max. value by this
window definition, and the annual stability of oil filled, hermetically
sealed Vishay types, I have checked on 5 EA VHP202Z over > 5 years,
meanwhile.
I was not aware of this ultra stable reference resistor inside my
instrument, as the 40k resistor in my unit was bent backwards, so I
could not read the type designator, and did not dare to touch it, up to now!
The old CLIP specifies this resistor as having 1.3ppm/K, so I always
assumed a Vishay k-foil of the 1989 era, non oil filled type.
Also the datsheet specified 1ppm/K (selected component), and 10ppm/year,
which also indicated the same type of hermetically sealed Vishay BMF.
So, this is a big surprise, no reason any more to change this reference
resistor.
HP did not change the specification, but the T.C. should be < 0.5ppm/K,
and <1ppm/yr for the Ohm ranges.
Frank
*
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In message 555E5D13.4060006@freenet.de, Frank Stellmach writes:
The VHP101 has [...]
I'd be surprised if HP didn't have a pretty hostile incoming inspection
procedure for this component, so I'd expect the specs of the onces that
made it into HP3458 instruments to be somewhat tighter.
I've always wondered what a company like HP did with rejects against
in-house-specs ? Did they have multiple grades so that the best
ended up in 3458, the next best in 3457 and the ones living up to
manufactureres spec in 3456 ?
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Poul-Henning Kamp schreef op 22-5-2015 om 10:22:
In message 555E5D13.4060006@freenet.de, Frank Stellmach writes:
The VHP101 has [...]
I'd be surprised if HP didn't have a pretty hostile incoming inspection
procedure for this component, so I'd expect the specs of the onces that
made it into HP3458 instruments to be somewhat tighter.
I've always wondered what a company like HP did with rejects against
in-house-specs ? Did they have multiple grades so that the best
ended up in 3458, the next best in 3457 and the ones living up to
manufactureres spec in 3456 ?
Most likely, they have Vishay do the selection for them.
As for rejects, there are no VHP101's in either the 3456 or the 3457 :)