Understanding Frequency Accuracy in Crystal Controlled Instruments

Synthesizers, vector network analyzers, frequency counters, spectrum analyzers and many other instruments must accurately create or measure frequency. However, their accuracy is affected by time, temperature, frequency and even gravity. This paper explains these effects in understandable terms and explains how to determine absolute frequency accuracy. This paper is not a thesis on crystal time base design; rather, it explains the external specifications of crystal time bases and how these specifications affect instrument performance. A frequency generation or measurement instrument must contain an internal frequency standard to which everything is referenced. It is called the time base standard. This standard is invariably a quartz crystal oscillator. The relative accuracy, size and cost of quartz crystal oscillators make them the time base standards of choice for instrumentation.