Date Codes can be misleading because most of this style of chip does not connect to the battery until the first power up cycle. So evl
Thomas Knox > Date: Thu, 27 Mar 2014 17:33:17 +0100 > From: [email protected] > To: [email protected] > Subject: [volt-nuts] 3458a RAM batteries - longer life if unit is > continually powered? > > Hi, > > the DALLAS datasheet specifies 10 years data retention. Quite obviously, > that's the unpowered time. > > That time includes self discharge and RAM sustaining currents. > > self discharge and RAM supply current will be of the same order, i.e. < > 1µA, I assume from experience. > And I assume also, that those currents will vary over samples, i.e. over > samples of battery and RAM. > > Recently, there was the case, where the CAL RAM was still alive after 24 > years (instrument vintage 1989, same DALLAS date code!), but with > unknown powering history. > > Additionally, a typical 10 years of lifetime is given also for those > batteries. > > Therefore, in practise there will be no pronounced difference between > powered / unpowered state. > On the other hand, DALLAS implemented an electronic seal, so that the > RAM inside the package is initially powered only after first power up. > But there's no parameter in the datasheet, specifying data retention > according to date code or to initial power up. > > > The waste of energy just to extend the batteries lifetime, does not pay off. > On the contrary, the MTBF time of the instrument will be consumed, the > display will get bad, and here in Germany, this energy consumption would > cost a fortune (meanwhile: 25+ Cents / kWh, crazy). > > > Yes, as long the instrument is powered, the CAL RAM will not lose its > content.. but what about unexpected power outages? > > > If you save the CAL RAM and repogram a fresh one after failure, there's > no need to send it to agilent. > > > No, not any RAM error needs recalibration. > Those error messages are not documented. > > So I've scanned the text fragments in the firmware file: > > RAM TEST 1 > RAM TEST 2 > > probably refer to either to the configuration RAMs (2x32kB), andthe CAL > RAM (8kB). > > Eror messages are: > NONVOLATILE RAM HiGH /LOW > CAL RAM FAILURE > > and known ones from other users: > > RAM TEST 1 HIGH / LOW > > So I assume, that a real failure of the cal constants only apply on > message: CAL RAM FAILURE and perhaps RAM TEST 2 ...., as RAM TEST 1 > should refer to the configuration RAMs only, HIGH to the high byte RAM, > LOW to the low byte RAM. > > Errors of the cal RAM will manifest in additional ACAL or CAL failures. > > > Frank > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
