Corey - These Seiko Epson RTC chips can and do fail (oscillator failure or moves “out of spec”). These chips have a rough accuracy of ~ 1 second/day. That level of accuracy can produce ~ 365 seconds/year (6 minutes)
Your question suggests that you are searching for a Clock with a higher frequency accuracy/stability — than this 1990s RTC solution provides (10-6). Seiko Epson RTC-72241 RTC - Full Datasheet http://www.s100computers.com/My%20System%20Pages/PIC&RTC%20Board/Epson%2072421%20manual.pdf Page 20 of the full datasheet provides insight & finding the frequency stability (time). 1.) Frequency and temperature characteristics can be approximated using the following equations. ** Finding the Frequency Stability ** ∆fT= α ( θT- θX)2 ∆fT : Frequency deviation in any temperature α (1/°C2) : Coefficient of secondary temperature ( −0.035±0.005 ) × 10-6 / °C2 θT ( °C ) : Ultimate temperature (+25±5 °C) θX ( °C ) : Any temperature 2.) To determine overall clock accuracy, add the frequency precision and voltage characteristics. ∆f/f= ∆f/fo+ ∆fT+ ∆fV ∆f/f : Clock accuracy (stable frequency) in any temperature and voltage. ∆f/fo : Frequency precision ∆fT : Frequency deviation in any temperature. ∆fV : Frequency deviation in any voltage. 3.) How to find the date difference Date Difference = ∆f/f × 86400(s) ** For example: ∆f/f = 11.574 × 10-6 is an error of approximately 1 second/day. ** — Greg == Date: Thu, 3 Oct 2019 00:00:44 -0500 From: Corey Sukalich <[email protected]> To: [email protected] Subject: [time-nuts] Timebase Replacement - Seiko Epson RTC-72421 My question pertains to a timebase used in a Schulmerich carillon bell tower system from the 1990’s. The Seiko Epson RTC-72421 Real Time Clock Module (4-bit) is used, but the clock ends up walking to a noticeable degree (minutes) over a period of months. Is this expected for the device in question, or could it possibly have a defect? Corey N9WIV _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
