High-g Time Bases

For many military applications, low-frequency oscillators are required which maintain their frequency within 5 parts in 104 after they have been exposed to an acceleration of 30 000 g and also after a storage period of 5 years. In addition, the same stability must exist while a constant acceleration of, say, 5000 g is applied. The characteristics of mechanical systems and various electrical circuits proposed for time bases will be summarized. It will be shown that oscillators, based on the use of RC networks and solid-state negative feedback amplifiers, can fulfill the requirements. It will also be shown that, for cost reduction, the conventional amplitude control over many cycles can be replaced by an instantaneous limiter without detrimental effects on stability. A hybrid timer, consisting of an electronic oscillator, synchronizing a spring-driven mechanical clock, is suggested.