[Isocops] Hi, Lo, CEU Input : IBEX Payload Limits

Paul Janzen paul.janzen at mso.umt.edu
Mon Jun 16 20:53:00 EDT 2014


> Attached is the revised set_payload_limits script. This will only set the
> red/yellow limits in MAESTRO (has nothing to do with autosafing, will
> just alert Sheral/Tim that they need to call me). The goal of this change
> is to remove the red OOLs during OFF conditions.
>
> The only change was to expand the low red OOL limit from -5 to -15 for
> the POS_7_5V_CEU_SWITCH_I. The Hi CEM voltage limits are still well above
> the new voltage. Do the current (I) limits have appropriate headroom too?

I approve the SOH.POS_7_5V_CEU_SWITCH_I change, for what it's worth, noting
that since it's a "CEU" telemetry point rather than a "-Hi" point, CEU
approval is the important one to get.

Nominal current draws for the Hi CEMs at the higher HVSCI operating
voltages (1780, 1780, 1780, 1900) are approximately 4.0, 3.6, 4.6, and
3.7 uA, which are all about 0.2 uA higher than the previous HVSCI operating
conditions.  (The highest gain test voltage for CEMs A, B, and C similarly
results in a current draw about 0.2 uA higher than those listed).
Individual SOH packets can occasionally be jumpy; the highest I've seen in
the last year (40 orbits) was 5.605 uA for one SOH packet on CEM C, back in
orbit 231, when CEM C was at 1780V (the preceding and following packets
reported lower and more typical currents of 4.650 and 4.711 uA; all four
CEMs were reported high by about the same offset for the one dubious
packet).  Aside from individual jumpy packets, the current is usually
stable well within a couple tenths of a uA.  Therefore I think there is
still sufficient headroom, and so the comment

+; 6/16/14 Removed red limits for 0/OFF values. Changed limits for new Hi CEM voltages.
+;       limits define   SOH.POS_7_5V_CEU_SWITCH_I  -15,  75, 124, 136

should not mention any changed limits for new Hi CEM voltages.


Paul Janzen.


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