Time Clock Owner's Manual

Documentation Number PCRTC2095 Manual 13
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
PH [phone] -- FAX [phone]
Aging
All crystal oscillators have an aging characteristic. The
crystal used in the PCRTC uses the coldweld manufacturing
technique, which exhibits the lowest aging characteristic of 1
ppm/year. In practice, this aging rate improves significantly with
time, but for practical purposes the value of 1 ppm is adequate.
To estimate the error in your application, sum the error from
the three sources above. This estimate can be used to determine
how frequently the time should be updated using Timeset or another
method.