Electronic Measurements

measurement of some electric, magnetic, or electromagnetic quantity or of the relationships between such quantities characterizing the operation of electronic equipment over the range of frequencies from the infrasonic to the superhigh.

Methods of electronic measurements were invented and developed simultaneously with the emergence and development of radio engineering and electronics and are based on the measuring methods used for electric quantities. Electronic measurements are necessary for the development, production, and use of equipment in radio communications, television, and radar, as well as for automation, technical troubleshooting, computer technology, and the manufacture of electronic instruments and components. The measurement techniques are used in physics, chemistry, biology, medicine, geology, and other scientific fields.

A distinctive feature of electronic measurements is the multiplicity of the quantities and the wide ranges of the values measured, for example, voltages of 10^-8 to 10³ volts, powers of 10^-16 to 10⁸ watts, and frequencies of 10⁴ to 10¹² hertz. In measuring the parameters of electronic equipment, it is often necessary to use indirect methods, requiring the use not only of measuring instruments but also of auxiliary apparatus, such as generators for voltage and current at various frequencies, operating in a continuous mode or with different types of oscillation modulation. Such equipment is also generally grouped together with electronic meters.

One of the most important areas in which electronic measurements are used is the measurement of parameters of electronic and radio components, such as resistors, capacitors, inductance coils, semiconductor devices, and integrated circuits. Other important uses are in determining the duty characteristics of semiconductor and electron-tube components, instruments, and apparatus with respect to current, voltage, and power; in determining the type and characteristics of variations in radio signals, including the shapes and spectra of pulse signals, the depth of modulation, the keying, and the deviation of continuous signals, and in studying the characteristics of electronic and radio-engineering equipment, including the amplitude of output signals as a function of frequency and time and the output power as a function of the load, the standing-wave ratio, and the shape of the radiation pattern of the antennas. Such measurements are also important in the grading and calibrating of electronic meters and electronic assemblies, apparatus, and systems, including signal generators, electron-tube voltmeters, wattmeters, radio receivers and transmitters, and radar sets; they are also used in measuring a variety of electrical parameters of materials and substances.

Electronic measurements are made under laboratory, production and field conditions. The instruments used for laboratory measurements feature high accuracy and stable parameters; they may have digital readouts of the measured quantities or dials with pointer indicators and manual adjustments.

Under production conditions, measurements are used mainly to check the parameters and characteristics of the items produced. Measuring equipment is now being used that automatically records the measurement results and, in a number of cases, transmits the results to a computer for further processing. Integrated measuring methods are being developed for usage in the so-called measurement-and-information systems that substantially (by hundreds of times) increase labor productivity in making the measurements, in management departments, and in other areas. These information systems fed by electronic measurements differ from other measurement-and-information systems in having, in addition to switching, recording, and computing devices, equipment that generates and transmits simulated (test) signals to the object being examined.

Under field conditions, electronic measurements are used for the immediate monitoring and measuring (with a limited accuracy) of the parameters of various radio devices or of the environment, particularly the noise level and radiation intensity. Portable electronic meters are generally used for this purpose.

The principal requirements of electronic meters are a small error, a negligible effect on the object of the measurement, high degree of reliability and operational readiness, and ease of use and repair. With the rapid development of electronics during the 1960’s, it became necessary to increase markedly the operation speed and frequency ranges of measurements, to introduce digital readouts, to minimize the number of controls needed, and to automate as much as possible the measurement process and feed results in digital form to a computer. In the early 1970’s, general-purpose electronic meters in the USSR and abroad included more than 1,000 types of different instruments, classified according to their purpose.

The voltmeter group includes both DC and AC types, as well as frequency-selective, phase-sensitive, pulse, general-purpose, and differential voltmeters. Instruments for power measurements include power meters, power bridges, thermistor devices, thermoelectric and bolometric transducers, and pyroelectric detectors.

The parameters of components and circuits having lumped constants are measured with inductance meters, capacitance meters, quality factor meters, ohmmeters, megohmmeters, and ground meters. The parameters of components and channels having distributed constants are measured by using slotted lines and instruments for measuring the standing-wave ratio, the reflection factor, the complex transfer constant, the impedance, and the admittance.

Frequencies are measured using wavemeters, heterodyne resonance indicators, and frequency meters; measurements are also made using the standard frequencies and instruments having an extremely high reproducibility for the given physical quantity; for hydrogen masers, this reproducibility is (1-5) × 10^-14. Also included in this group of instruments are frequency synthesizers, calibrators, frequency converters, and frequency synchronizers for radio signals.

Phase shift and group-path time delay are measured with phase meters and meters that measure the transit time of signals at different frequencies. Instruments have been adopted for observing and studying the shapes and spectra of signals. This group includes cathode-ray oscillographs, modulation meters, deviation meters, spectrum and harmonic analyzers, and nonlinear distortion meters. Also in this group are instruments for measuring the gain-frequency, phase-frequency, and correlation characteristics of electronic equipment, as well as the noise factor.

More and more attention is being given to the development of a particular group of instruments in modern measurement technology designed for pulse measurements, including meters for measuring time intervals, pulse duration, and the leading and trailing edges of pulses, pulse counters, and pulse-amplitude analyzers. During the 1970’s, instruments also appeared for holographic measurements and for parameter measurements of equipment operating at low temperatures.

Of great importance in electronic measurements are instruments that receive, amplify, and generate radio signals, including radiometer receivers, AC and DC amplifiers, wide-band, selective, and general-purpose amplifiers, instruments and equipment for antenna measurements, signal generators, noise generators, sweep generators, and generators for special signal forms, such as square-waves and sawtooth waves, whether or not they are the envelopes of a carrier.

For production needs and operating services, there are instruments that measure the parameters of semiconductor diodes, transistors, and integrated microcircuits, as well as measurement-and-information systems designed for large-scale measurements, where high accuracy and productivity are both important. Cathode-ray curve tracers are used for making rapid measurements of the parameters and characteristics of electronic devices.

Auxiliary equipment in the form of functional units is employed to connect the electronic meters with the objects of the measurement. Such equipment includes modules of coaxial, strip, or wave-guide lines, E-H tuners, conversion (bullet) and balun transformers, wave-guide-to-coaxial and strip-line-to-coaxial adapters, mechanical and electric switches for coaxial and wave-guide lines, attenuators, directional couplers, phase shifters, detector-converters, ferrite circulators and isolators, filters, loads, short-circuiting devices, and connecting units. Practically all these components are used in three versions: waveguide, coaxial, and strip line.

Electronic meters are also used in combination with various converters to determine certain nonelectric quantities, such as linear dimensions, temperatures, and pressures.