Quantities and units of periodic and related phenomena
1Key Takeaways
This standard specifies the names and symbols of the quantities and units of periods and related phenomena; where appropriate, conversion factors are given. This standard applies to all fields of science and technology.
2Expert Interpretation
An in-depth interpretation of the 17 core quantities of periodic phenomena and their unit systems in the GB 3102.2-93 standard, including international standardized definitions and engineering application comparisons of key parameters such as frequency, wavelength, and damping coefficient, with special explanation of the conversion relationship between complex number representation and logarithmic units.
Standard Framework and Technology Evolution
This standard is equivalent to the ISO31-2:1992 international standard and constitutes a key component of my country's measurement system. Together with other standards in the GB3100 series, it constitutes a complete physical quantity expression system, reflecting the results of the unit system reform after the implementation of the Measurement Law in 1984.
Core quantity comparison table
| Quantity name | Symbol | SI unit | Non-SI legal unit |
|---|---|---|---|
| Period | T | Second(s) | - |
| Frequency | f,ν | Hertz(Hz) | Revolution/minute(r/min) |
| Angular frequency | ω | rad/s | - |
| Damping coefficient | δ | s-1 | Np/s |
Key Technical Points
Complex Number Representation Specification
The standard clearly stipulates two equivalent representations of damped oscillation:
- Real number form: F(t)=Ae-δtcos(ωt)
- Complex number form: Re[Ae-(δ+jω)t]
Where δ and ω must use the exponential function of the natural logarithm base e to ensure dimensional consistency (s-1).
Logarithmic Unit Conversion
Definition differences between field magnitude and power magnitude:
| Type | Definition formula | 1 unit corresponding ratio |
|---|---|---|
| Field magnitude | LF=ln(F/F0) | 1Np→e≈2.718 times |
| Power magnitude | LP=½ln(P/P0) | 1Np→e2≈7.389 times |
Accurate conversion between decibel and neper: 1dB = (ln10)/20 Np ≈ 0.115Np
Project implementation suggestions
- When measuring vibration, the Hz unit of the frequency analyzer should be used first. For rotating machinery, r/min can be retained
- It is recommended to uniformly use Np/m for electromagnetic wave attenuation calculation, which is consistent with ISO standards
- The phase angle should be clearly marked in radians (rad) or degrees (°) to avoid dimensionless values