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@ -59,10 +59,10 @@ Another healthy upgrade I did was to update the firmware to the latest version,
## U180 drift evaluation ## U180 drift evaluation
Now the big question with any 3458A project is whether the U180 ADC ASIC at the heart of the meter is still in good condition. This requires an extensive check, powering the meter and monitoring the calibration constants from the ACAL DCV. For this, a toolkit was written. And although this is a rather short data capture, several captures were made. All with similar results in terms of the drift observed. Now the big question with any 3458A project is whether the U180 ADC ASIC at the heart of the meter is still in good condition. This requires an extensive check, powering the meter and monitoring the calibration constants from the ACAL DCV. For this, a toolkit was written. And although this is a rather short data capture, several captures were made. All with similar results in terms of the drift observed.
In terms of the [infamous service note 18](3458-WorkLog/Sn18A.pdf) this meter passes, though it is not a "golden" meter by any means at this point in time. But great that it's not failing this and not permanently out of the manufacturer's specifications.
![u180-drift](3458-WorkLog/u180-drift.png) ![u180-drift](3458-WorkLog/u180-drift.png)
In terms of the [infamous service note 18](3458-WorkLog/Sn18A.pdf) this meter passes, though it is not a golden meter by any means. But excellent that it's not failing this and not permanently out of spec.
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## Improving ## Improving
If one looks at semiconductor ageing there are a few things we can do to improve the stability in the long term. If one looks at semiconductor ageing there are a few things we can do to improve the stability in the long term.
Firstly, it is possible to lower the current passing trough the reference devices on the die, this in turn will decrease the drift experienced from electromigration. This is the movement of material caused by electons bumping into them. Thus this could be lessened by decreasing the amount of electrons troughout the device by decreasing the amount of current. This coming at the tradeoff of extra noise. Firstly, it is possible to lower the current passing trough the reference devices on the die, this in turn will decrease the drift experienced from electromigration. This is the movement of material caused by electons bumping into them. Thus this could be lessened by decreasing the amount of electrons troughout the device by decreasing the amount of current. This coming at the tradeoff of extra noise.