Showing papers on "Frequency counter published in 1974"

Surface acoustic wave transducer

Abstract: Surface acoustic waves are propagated across a thin, flexible diaphragm which is subjected to an applied external pressure. Since the wave velocity and path length vary with diaphragm deformation, the acoustic wave delay time is a function of the applied external pressure. Electroacoustic transducers are fabricated on opposite edges of the diaphragm for electronic excitation and detection of the surface acoustic wave. An electronic feedback path including the two transducers, the wave path, and an electronic amplifier oscillates at a frequency which is determined by the delay time required for acoustic wave propagation over the diaphragm path, and which decreases approximately linearly with applied external pressure. A second acoustic path called the reference path has a length equal to the first path and in the preferred embodiment contains a diaphragm which is subject to a different applied pressure. A second electronic feedback path composed of two transducers, the reference path and a second amplifier oscillates at a second frequency called the reference frequency. By applying a sample of the first and second oscillator voltages to a semiconductor mixer, a difference frequency output is obtained which is proportional to the differential pressure. The difference frequency output is approximately independent of temperature, and is easily converted to various digital codes by use of standard frequency counter circuits. If only one set of transducers is used, the device can also measure temperature in a digital manner. By adding a mass load to the center of the diaphragm, acceleration may be measured. Stress or strain measurements may also be made by bonding the diaphragms or only the transducers directly on the physical surface to be measured.

Automatic ranging frequency counter

Abstract: An automatic ranging frequency counter comprising a counting register which counts an unknown frequency signal for a measured amount of time. A frequency range detector indicates to a sequence controller and a decade time interval gate the degree of filling of the counter register at the end of said measured amount of time. The sequence controller and decade time interval gate control the commencement and duration of the measured amount of time. When the counting register attains a specific degree of filling after the termination of the measured amount of time, the contents of the counting register are displayed. The measured amount of time is initially small and is increased by decades until the correct frequency range is found, thereby providing the fastest operating speed possible.

Fractional frequency dividers

Abstract: A frequency divider for dividing a frequency in the ratio or fraction whose numerator is 2 and whose denominator is an odd number which comprises a counter circuit for counting input clock pulses; a device connected to the output terminal of the counter circuit so as to deliver a reset signal to the counter circuit when it counts a prescribed number of clock pulses; and a device for supplying a polarity-reversed clock pulse to the counter circuit upon receipt of the reset signal.

Television receiver with pattern generator

Abstract: A pattern generator for a color television receiver which utilizes a digital counter to count scanning lines and produce an output pulse every ninth and tenth scan. An oscillator coupled to the horizontal deflection voltage produces pulses at a repetition rate which is substantially higher than the scan frequency. The high frequency pulses from the oscillator are then combined with the output of the counter to produce either a crosshatch or a dot pattern on the screen. The crosshatch pattern is developed when both the oscillator and counter outputs are continually fed to the television video circuit, and the dot pattern is produced by coupling a signal to the video circuit only upon the simultaneous occurrence of both the oscillator and the counter pulse outputs.

A system for the investigation of nonlinear dielectric effects using digital techniques

Abstract: A novel method for the study of nonlinear dielectric effects has been developed, which allows, for the first time, measurements to be carried out on conductive media such as water. The sample is contained in a dielectric cell which is part of the tank circuit of an oscillator. A rectangular electric field pulse of up to 15 MV m-1 is applied to the sample, and the resulting frequency change of the oscillator due to the nonlinear dielectric effect is measured using a computing frequency counter. This frequency change is simply related to the change in relative permittivity Delta epsilon . By sampling the frequency of the oscillator at different points throughout the duration of the electric field pulse, a very faithful reproduction of the profile of the nonlinear effect can be built up. Details are given of the instrumentation along with illustrative results for diethyl ether.

Readout apparatus for frequency or period-analog measuring signals

Abstract: In the case of frequency-analog measuring values the readout apparatus must be calibrated with respect to two reference points. The readout apparatus comprises a reversible counter, whose counting input for the one counting direction receives the measuring pulse train during a first time interval and whose counting input for the other counting direction receives a reference pulse train during a second time interval. The reference frequency is equalized to the measuring frequency for one reference point and the counter is set to said initial value at the beginning. The time intervals, which are equal and which coincide, are adjusted so with respect to a second reference point, that the counter indicates the desired value. The time intervals are determined in a control counter by a clock frequency. However, for period-analog measuring signals the reversible counter counts the clock frequency, and the measuring frequency and the reference frequency are applied to the control counter.

High frequency counter having signal level sensitivity

Abstract: An improved circuit at the input of a high frequency counter includes a bias-sensitive binary divider in the input stage and includes circuitry for altering the bias on the binary divider to change sensitivity automatically as a function of applied signal level.

Dielectric Loss in Coaxial Cables via Phase Delay Measurements

Abstract: Determining dielectric loss as a function of frequency in high frequency coaxial cables is a requirement for efficient design of long cable systems. A method for determining dielectric loss based on attenuation and phase delay measurements along with low frequency capacitance data and nominal cable specifications is presented in Part I. The pi-point method of making precision phase delay measurements is reviewed and contrasted to earlier methods in Part II. A 10-nmi-length of SF ocean cable at frequencies up to 10 MHz is considered as an example. For this case the number of wavelengths N is approximately 1000 at 10 MHz. A measurement technique is described and a test setup, including circuitry, is presented for making pi-point phase measurements and for determining N with zero error. Measurement errors, converted to equivalent frequency errors, with detector noise, mismatch, attenuator phase shift, and frequency counter errors being the significant contributors are considered in Part III. When all worst case errors are added, the accuracy of the delay measurement is better than 0.3 ppm at 10 MHz for the sample case under study.