frequency standard

elektor electronics september 1985 GE Dunning 62 ... 1.ooooos s• A frequency standard is a stable and precise oscillator that is calibrated against national or international reference frequencies which are often broadcast as time signals throughout the day; in many countries, such reference signals are also available over the telephone. These reference frequencies deviate by not more than 1 second per 3170 years. The clock used in the SI definition of the second is 100 times better still! A frequency standard is used, for instance, to check the calibration accuracy of various measuring instruments. For this purpose, an accuracy of about 1 p.p.m. is normally perfectly adequate. frequency standard A quartz-controlled digital watch, syn- chronized to a radio or telephone refer- ence time signal over a period of time, is a convenient and inexpensive basis for a frequency standard. Such a watch com- monly deviates not more than 1.. .2 seconds per month from true time, which is an acc...