Re: 2440 nvram (was: NVRAM back-up battery change on a 2715..... avoiding disasters)


On Sat, Nov 9, 2019 at 08:39 PM, Szabolcs Szigeti wrote:

I think what the SM says here is when you press the button, it recalculates some values and
writes it to the nvram.
Quite likely.

But this needs to be done after every change in setting the pots.
True for the operational settings, not true for the Adjustment (chapter 5) data that is stored in the "store..." menus during Adjustment.

So for the original question of is there a real need to save the 2440 nvram
when _it is in cal_ but the nvram needs to be changed, the answer is no, as
the scope can be brought back to calibrated state by running the self cal and ext cal.
Here I disagree.
If this were true, what purpose would the menu-supported adjustments (like setting numbers, turning external pots) and storing by pressing keys etc., see msg #161473, during manual calibration ("Adjustment", chapter 5) serve? They are quite different from the saving of operational settings, which happen all the time during use.
In these respects, the NVRAM function is quite comparable to that in 'scopes like the 2445/65 series. Calibration constants are stored in NVRAM, as are the operational settings. The latter change all the time when working with the 'scope, whereas the former cannot be restored by just pressing a button: The scope needs to be Adjusted as per SM chapter 5. Many 'scopes also store user-initiated attenuator offset corrections in NVRAM.

...the scope can be brought back to calibrated state by running the self cal and ext cal.
Not if the constants that were set during Adjustment (chapter 5) were lost because of exchanging the NVRAM , unless the 'scope does have another place to store them. It seems that we don't know where that would be in this model.


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