Warning:
non photographic OM engineering content follows.
wright@xxxxxxxxxxxx writes:
<<
>the
>analog TTL can react faster that the digital circuits in the 4T.
>
Ah yes, I'm a fan of analog circuitry. Long rule analog@!@!
>>
Dirk,
The OM2S and OM4 are both pretty analog despite the microprocessors
in both. The 2S and 4 might well have slower comparators/buffers for the TTL
but they don't delay the quench signal through the software decision of the
processor. The processors run pretty slowly for that. The basic building
block circuits in the OM2S for example, are almost identical to the OM2.
Consisting of an analog current (light ) integrator followed by an analog
comparator feeding the shutter magnet/quench signal output. The reference
signal the comparator uses in the OM2S is generated digitally from a DAC
rather than the resistors in the OM2.
However, unlike the OM2 the OM2S sets the manual shutter speeds purely
digitally with a counter. I have not checked the OM4 schematic but form a
comment in one of the OM documents I believe the OM4 does not use a digital
counter like the 2S for manual shutter speeds. If this is true, the OM2S may
be "more" digital than the OM4!
Regards,
Tim Hughes
>>Hi100@xxxxxxx<<
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