Abstract: A method and apparatus for the measuring of a delay in a delay circuit by making a continuous frequency measurement is proposed. The phase-locking of a variable frequency signal applied to the delay circuit allows the user to significantly improve the precision and accuracy of the time delay measurement. A scheme to extract the number of cycles stored in the delay circuit is also disclosed.

Abstract: A circuit for time stamping event signals, e.g. zero-crossings, using coarse and fine timers. The fine timer is a circuit section which subdivides a period from a phase-locked ring-oscillator into 2N subparts. An event signal is timed by latching a digital representation of a particular subpart. The digital representation of the subpart is an N-bit dual thermometer code which uniquely identifies each subpart with each adjacent subpart differing by only one bit. The subparts are made finer in time quantization than the propagation delay of one active element in the ring oscillator by the use of linear combiner elements. The dual thermometer code, encoded post-latching into a binary code, forms the "fine" timing part of a binary word representation of the event time. The event also latches the count states of a pair of lead-lag counters in a master-slave configuration counting ring oscillator periods. These counters change states respectively before and after the dual thermometer code turn-overs.

Abstract: A time interval measuring apparatus is provided for measuring the time interval between two signals. The two signals are successively brought to synchronization by delaying one of the two signals as they pass through a series of time shift cells connected in tandem. These delays are accumulated in a register, and the total net delay which is required to bring the two signals into synchronization is indicative of the time interval between the two signals. This indication of the time interval between the two signals thus forms the time interval measurement thereof. It can be refined by increasing the number of time shift cells in tandem and using progressively finer delays.

Abstract: A method of sampling accurately the instantaneous content of a high speed counter without interrupting the counting process is provided. The method is applicable even when the higher order digits of the counter are constructed by slower switching circuits configured in either a synchronous or ripple-through arrangement. The switching and carry propagation times of these higher order counters need not be shorter than the time between successive events being counted. Sampling of the contents may be made repeatedly in the interim without affecting the totality of the final count.

Abstract: A method is provided for measuring a single-shot time interval using startable oscillators to replicate indefinitely the time interval for averaging. Also provided is a circuit for automatically selecting a proper ratio of division to ensure that the interval being measured is less than the period of replication.

Abstract: Measurement of a time interval between a start and a stop event is made by activating a start oscillator in response to the start event and activating a stop oscillator in response to the stop event. The number of cycles of each respective oscillator signal which occur between the activation of each oscillator and the coincidence of the respective oscillator signal with that of an independent time base is determined. The number of cycles of the time base signal between the coincident points of it and the start and stop oscillator signal is also determined. These numbers, which are always integers, are used along with the values for the time base period and the difference in frequency between the time base oscillator and the start and stop oscillators to calculate the time interval. Resolution of the measurement is dependent on the frequency difference between the time base signal and the start and stop oscillator signals.

Abstract: An automatic transfer oscillator system for frequency measurement using a single sampler is described. Two signals, of frequencies f.sub.1 and f.sub.2, are alternately used to drive the sampler. The two frequencies are sufficiently close by design so that the intermediate frequency signals generated arise from the same harmonic number when sampling a signal of unknown frequency f.sub.x. The resulting average IF output is accurately measured and used to compute the unknown frequency f.sub.x. Accurate measurement of the average IF output is made possible because the transition between f.sub.1 driving the sampler and f.sub.2 driving the sampler only occurs when the two signals are in phase. As a result, the IF signal transitions are also in phase and spurious signals are not produced. This technique is referred to as phase continuous switching.

Abstract: A measurement averaging counting apparatus employing a randomly phase modulated time base provides resolution improvement when measuring an applied signal comprising time intervals or pulsed frequencies repetitively occurring at rates synchronous to a counter's clock frequency.The phase of a reference frequency is varied in response to a random signal. The phase modulated reference frequency is applied to a frequency multiplier chain which multiplies both the frequency and the effective amount of phase modulation. The randomly phase shifting output of the frequency multiplier chain is applied as a clock signal to a measurement averaging counter thereby destroying coherence between the clock signal and the applied signal and allowing statistical averaging to take place.