[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system
bob at evoria.net
Sat Nov 1 00:38:31 EDT 2014
Hi Bob et al,
I don't understand the direction this question about the supercap has taken. It's connected to pin 1 of the GPS receiver. It looks to be a UT+, so that's the battery backup power. According to my UT+ manual the current draw on this pin is between 5uA (at 2.5V) and 100uA (at 5V)? How many hours will a .022F supercap keep at least 2.5V at that sort of discharge rate? Unless the cap has gone bad, it seems more likely that Bob's comment about it doing a fast survey and then doing a slower one in the background probably has merit. In fact, my unit goes through its survey mode pretty quickly on power up. So do those current/voltage figures imply several hours on the cap?
From: Bob Camp <kb8tq at n1k.org>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Friday, October 31, 2014 9:22 PM
Subject: Re: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system
I sort of doubt that a GPS aux supply is quite that low current. I have seen some RTC’s that won’t last a month on a coin cell. My recollection is that the Oncore backup is closer to that category than the “many years on a cap” group.
> On Oct 31, 2014, at 9:26 PM, Brooke Clarke <brooke at pacific.net> wrote:
> Hi Bob:
> When HP came out with the 300 series Rocky Mountain Basic computers they were fitted with a super cap to power the RTC.
> I will keep time for some months.
> Mail_Attachment --
> Have Fun,
> Brooke Clarke
> Bob Camp wrote:
>> The ultra cap is a pretty small one (physical small). You might be able to find a larger (more farads) one that would fit in the same space. It’s not going to help for a hours and hours sort of outage. It might get you from dying in 15 minutes to dying in a half hour.
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