Digital Frequency Meter Research Articles

Custom designed LSI for instrumentation

During the 1970s the demands of the electronics and communications industries for high precision instrumentation at competitive prices set new problems for the instrument design engineer. Faced with a challenge to provide accuracy, reliability and versatility in widely different environments and applications an early decision was made to explore the latest technology for digital frequency meters and universal counter-timers. This paper discusses the consequences of this decision.

A simple and inexpensive method of measuring thin film thicknesses

A simple apparatus is described which makes use of quartz crystal oscillator and a digital frequency meter to measure thicknesses of vacuum-deposited films. Experimental results are presented which show that film thicknesses as measured with this apparatus proved more accurate than those measured with a commercial film thickness monitor. Such an apparatus is economically attractive and its versatility gives it many useful advantages not present with commercial monitors.

Digital frequency meter for burst-like laser Doppler signals

A new frequency meter employing a period-measuring method has been developed for a burst-like laser Doppler beat signal. It does not process the Doppler beat signal as a continuous signal, but detects whether each beat signal cycle is a true or a false signal, and measures the signal frequency. It not only follows the frequency changing of each cycle of the Doppler beat signal but also calculates a mean signal frequency within a certain time. The parameter setting of this frequency meter is far easier than for a system employing a bandpass filter.

The counter-timer—a powerful measuring instrument

The modern counter-timer, a natural development of the digital frequency meter, will perform a variety of functions besides basic measurement of frequency. With the aid of transducers, a single instrument can be used in the measurements of widely differing quantities.

Automatic resonant frequency meter

An automatic frequency meter was desgined for operation with a commercial electronic bridge or potentiometer. It can be used as a secondary instrument with high-frequency conductometers, hygrometers, level indicators, etc. The utilization of such instruments will narrow the application range of expensive digital frequency meters.

On an investigation of slow frequency fluctuations

The possibilities of an experimental investigation of the frequency fluctuations of the oscillations are considered by means of a digital electronic frequency meter. A comparison is made of the results of the measurements with the spectrum of the fluctuations, and an analysis of the errors of the measurements is likewise carried out.

A method of measuring pulse duration

The pulse under investigation and a timing wave consisting of a succession of narrow triangular pulses of controllable frequency are simultaneously displayed on a double-beam sampling oscilloscope. Adjacent timing pulses are aligned to the leading and trailing edges of the pulse being measured; the duration of the pulse, being then identical with the period of the timing wave, is obtained from a digital frequency meter monitoring the timing-wave frequency. Pulse durations in the range 20 to 100 ns may be determined with an uncertainty of ± 100 ps. For pulses of durations extending to several microseconds the uncertainty is within ± 0.1%. The method has particular application in pulse-bandwidth measurements on television and other waveform transmission systems having pulse bandwidths in the range 125 kHz to 25 MHz. Using ancillary amplitude-measuring equipment, such measurements can be accomplished with uncertainties of ±1% or better.

An accurate voltage-to-frequency converter

A current- or voltage-to-frequency converter is described for converting analogue signals into a pulse form in which the pulse repetition frequency is proportional to the instantaneous signal amplitude. The conversion is linear to within 0·01% over the frequency range 0-10 kHz (or 0-1 kHz), and to within 0·1% up to 50 kHz. Thermal stability is comparable. The circuit action is based on continuous integration of the input signal, and the converter may be used as an interface in signal processing, or as an integrator, or for converting a digital frequency meter into a digital voltmeter with 10 μV resolution. It may also be used in reverse as an accurate count-rate meter (frequency-to-voltage conversion).

Errors introduced by transistor switches into digital Wien-bridge frequency meters

Errors introduced by transistor switches into digital Wien-bridge frequency meters

Combined generator and digital frequency meter with a pulse-phase automatic trimming

Combined generator and digital frequency meter with a pulse-phase automatic trimming

Testing frequency meters by means of an electronic digital frequency meter

Testing frequency meters by means of an electronic digital frequency meter

Digital frequency meter, Type SA.505

Digital frequency meter, Type SA.505