HP HP-Bench-Briefs-1994-04-06 free download

File name HP-Bench-Briefs-1994-04-06.pdf

HEWLETT PACKARD SERVICE INFORMATION FROM HEWLETT-PACKARD 2nd Quarter 1994 CaAibraltiom of Time Base Oscillators Jim BechtoldlEditor of 9,192,631,770 periods of transition bration interval within the cesium atom." Frequency is Determination of the effects of noise determined by counting the number of in frequency generating equipment cycles over the period of a second. Therefore, the definition of a clock can Determination of the effects of be expressed as a device that counts the changing environmental conditions number of seconds occurring from an arbitrary starting time. This Article Prior to analyzing the effects and im- From this definition it appears that a pact of the above sources of error, it is clock needs three basic parts. First, a necessary to determine the level of ac- source of events to be counted. This curacy required and the tolerances es- source can be labeled a frequency stan- sential for the individual application. Counting and Clocks dard, frequency source, or time inter- Once the essential tolerances have been val standard. Second, a means of accu- established, the sources of error can be Counting intervals has been going on mulating these events or oscillations. since man's beginning. Early time mea- analyzed to determine if they have an Third, a means of displaying the accu- impact on system operation. If they do, surements involved counting the num- mulation of time. Figure 1 shows a ber of days in terms of sunrises, sun- in fact, affect the system operation, then simple clock block diagram, including appropriate steps can be taken to re- sets, or moons. Later, the day was di- a method of presetting the arbitrary vided into smaller incrementsby using duce that impact. This article will de- starting time and obtaining an electri- scribe the frequency calibration inter- an hourgla