HP41C/CV Time module accuracy factor

[Boub65]

Hi all,
I have a question concerning the Accuracy Factor of a given time module.

Does it depend on the time module only (i.e. it's quartz) or also on the calculator (i.e. it's LC value)?

For example, if I have a accuracy factor for a given time module in one of my HP41*, can I use the same accuracy factor if I move the module to another calculator? Or do I have to recalculate?

[Monte Dalrymple]

(02-22-2023 08:41 PM)Boub65 Wrote:  Hi all,
I have a question concerning the Accuracy Factor of a given time module.

Does it depend on the time module only (i.e. it's quartz) or also on the calculator (i.e. it's LC value)?

For example, if I have a accuracy factor for a given time module in one of my HP41*, can I use the same accuracy factor if I move the module to another calculator? Or do I have to recalculate?

The AF is specific to the crystal oscillator in the Time Module itself, so it should stay fairly constant across machines. The condition of the batteries will probably have some effect, but that's all.

[Allen]

Quote: The condition of the batteries will probably have some effect, but that's all.

I would guess the Allan Variance of the crystal oscillators is pretty sloppy by today's standards, especially if the calc was not at room temperature.

I'd be surprised if the cost/power/size/availability at the time would have allowed them to use a TCXO rather than a standard crystal, but that would be an improvement!

[Garth Wilson]

Have any of you really needed to use it?  My 1986 41cx's time keeping has been super accurate even without applying the AF.  I go many years at a time without having to do anything except apply the change to daylight savings and back.

[cortopar]

I wear mechanical wristwatches, exclusively. So, my accuracy demands are fairly low, comparatively speaking. TCXO would be overkill for a calculator for me. I have a bunch of 17bii and 41CX, and they’re all close enough.