Author Topic: HP 3458A repair log  (Read 2649 times)

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Offline Samogon

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Re: HP 3458A repair log
« Reply #25 on: April 05, 2018, 05:46:30 am »
I have better idea.
I will use power meter 4418B with sensor 8482A and attenuator 30dB
At least it will give me rougly .5% uncertainty way better than 3% still not that good as expensive thermal converters.
 

Offline Samogon

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Re: HP 3458A repair log
« Reply #26 on: April 05, 2018, 01:43:14 pm »
Well, overnight it drifted again for almost  2ppm.
 

Online alm

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Re: HP 3458A repair log
« Reply #27 on: April 14, 2018, 10:11:22 am »
What drifted? ADC relative to internal reference (CAL72)? Internal reference relative to Keithley 2002 or other external reference (how do you know which of the two drifted)? Is this with our without ACAL every 24h/1°C change in temperature?
 

Offline Samogon

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Re: HP 3458A repair log
« Reply #28 on: April 14, 2018, 10:13:07 pm »
Conclusion based on collection of data and daily CAL72 value change baded on formula probided in sevice note 18A where seven day drift should be below 0.43ppm per day mine showed 1.5ppm
 

Online Kleinstein

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Re: HP 3458A repair log
« Reply #29 on: April 16, 2018, 03:56:03 pm »
For the initial few weeks after the meter was not used for a long time, there may be some extra drift, that may be not so critical. There can also be some temperature dependence on the cal72 value. To really get reliable drift of cal72 it would need values at the same temperature.
 

Offline Samogon

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Re: HP 3458A repair log
« Reply #30 on: April 16, 2018, 04:17:02 pm »
Ambient temperature  was stable +/- 1 degree. while CAL72 was steadily drifting down and no temperature correlation.
Per SN18 it is enough to run 7 days test to see if CAL72 out of tolerance.
The only thing i did not test is measuring directly internal reference stability.
 


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