China
Africa
Explore chapters and articles related to this topic
Precision frequency meter for basic metrology and displacement measurements
Published in Kennis Chan, Testing and Measurement: Techniques and Applications, 2015
V. Zhmud, A. Goncharenko, A.V. Liapidevskiy
Relevance of high-precision frequency measurements for di erent time intervals is a consequence of the need to develop a global satellite navigation system GLONASS, where high-precision measurements of distances require time or frequency standards of according precision. Available frequency standards do not agree to the requirements because their relative uncertainty is the unit of the 14-th sign, whereas this system requires frequency standards with the accuracy of the order of one of the 18-th sign. Therefore, the leading research teams carry out extensive research to create a prototype of a new generation of the frequency standard, which would provide the required accuracy. Certification of such standards requires precision frequency meters. The validation procedure uses two or more standard, and this frequency di erence is formed by the heterodyne mixing which by mixing or directly is transferred to a carrier frequency, su ciently stable for the subsequent measurement. The accuracy requirements to the frequency counters used for this measuring are in this case not so high, namely, the error of frequency counters should be not more than one unit of the 10-th sign. But the following additional requirements arise. 1 Measuring intervals must vary from ultra-small (less than 0.001 s) to very large-scale (more than 1000 s) values. 2 Dead time between the measurement intervals is unacceptable. 3 The possibility of simultaneous measurement of multiple frequencies a single device is desirable
Test equipment
Published in Joe Cieszynski, David Fox, Electronics for Service Engineers, 2012
As the name implies, this piece of test equipment is used to measure the frequency of sinusoidal or squarewave signals, and although this can be done using an oscilloscope, the frequency counter is far more accurate, especially at higher frequencies.
Dry aerosol particle deposition on indoor surfaces: Review of direct measurement techniques
Published in Aerosol Science and Technology, 2022
Surface Acoustic Wave (SAW) sensors are miniaturized devices used in R&D studies, which means that they are not ready-to-use sensors: mass deposited on their surface can be correlated to a shift in frequency correlated to a mass load. All acoustic wave mass sensors are composed of a piezoelectric part that produces an acoustic wave. By studying the velocity and amplitude changes of the acoustic wave, deductions can be made regarding resonance frequency. Frequency is measured using a frequency counter. The precision of the counter depends on its timebase stability. Precision is also enhanced by measuring over a long time period. All acoustic wave mass sensors play the role of deposition surface.