High-Stability Measuring Oscillator G-4
Abstract Generated abstract
The article describes the G-4 high-stability measuring generator, a sinusoidal voltage source intended to provide low harmonic distortion, stable output voltage, and relatively high output power over a 20 Hz to 50 kHz frequency range. Its design combines a Wien-bridge master oscillator, a cascade power amplifier, automatic voltage regulation through an average-value converter, a photoelectric controlled feedback element, and a Williams-type reference voltage source with temperature compensation and passive thermostating. Reported certification data indicate output-voltage instability below 0.001 percent over both 5 minutes and 1.5 hours, with nonlinear distortion below 0.1 percent and selectable output levels of 10, 30, and 100 V.
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HIGH-STABILITY MEASURING GENERATOR G-4
V. R. TSIBULSKII, V. A. BUTENKO
(Presented by the scientific seminar of the Department of Radio Engineering)
The G-4 generator is a high-stability source of sinusoidal voltage with a low harmonic content and a sufficiently powerful output.
The design of the generator is based on a method of automatic voltage regulation using an average-value converter in the feedback circuit and a photoelectric controlled element. Figure 1 shows the schematic diagram of the G-4.
The master oscillator is an oscillator with a Wien bridge. A special incandescent lamp is used as the inertial nonlinear element in the feedback circuit, owing to which the nonlinear distortions at a frequency of 20 Hz do not exceed 0.07%. The power amplifier is assembled according to a cascade circuit with parallel control. The voltage gain is 10. Its distinctive feature is that the feedback resistance of the amplifier
\[ R = R_1 \parallel R_{\phi} \]
is at the same time also the controlled element of the overall feedback loop. The average-value converter is a diode rectifier with temperature compensation and has high time and temperature stability.
The next element determining the stability of the output voltage of the entire device is the reference source. The latter is assembled according to the Williams circuit [1], using KS196V voltage stabilizers, which have guaranteed stability.
The use of an average-value converter made it possible to create a sufficiently high-resistance comparison circuit after the converter and, consequently, to have a small current consumption from the reference source. Under this condition the Williams circuit gives a stabilization factor of \(10^3 \div 10^4\) and preserves the temperature properties of the voltage stabilizers used. For KS196V voltage stabilizers the temperature coefficient of voltage is \(0.001\%/^\circ\mathrm{C}\). To obtain high temperature stability of the entire generator, through temperature compensation was used by including an additional diode and variable resistance \(R_3\).
As the isolation amplifier, an integrated circuit 1UT401A was used, making it possible to operate the AL102A light-emitting diode without additional matching elements. To eliminate the influence of rapid fluctuations of the ambient temperature, the converter, the isolation amplifier, and the reference source are placed in a passive thermostat.
Fig. 1.
The G-4 generator has been verified, certified, and is operated by the D. I. Mendeleev All-Union Scientific Research Institute of Metrology in Leningrad. According to VNIIM data, the mean value of the instability of the output voltage over 5 minutes is less than 0.001%; over 1.5 hours, 0.001%.
Technical Characteristics of the G-4
- Frequency range: 20 Hz–50 kHz.
- Output-voltage levels: 10, 30, and 100 V, adjustable by ±5%.
- Output-voltage instability: less than 0.001%.
- Nonlinear-distortion coefficient: less than 0.1%.
- Output power: 2 W.
REFERENCES
- R. Williams. High-stability source of reference voltage for direct current. Elektronika, 1969, No. 9, p. 135.