Overview of Core Differences Between Pt100 GOST 6651-2009 and IEC 60751
The temperature measurement range and minimum span (10K) of the two Pt100 temperature sensors are completely identical, but the core differences lie in the governing standards, α temperature coefficient, resistance-temperature graduation curve, and the interchangeability of associated instruments. The following explains this in detail from 6 aspects.
1. Different Governing Standard Systems
- Pt100 GOST 6651-2009 α=0.003910: Russian national standard, applicable to CIS and Russian-system equipment, adopts the traditional high-purity platinum graduation curve of the former Soviet Union, commonly known as the 391 curve.
- Pt100 IEC 60751 α=0.00385: International general electrotechnical standard, adopted by the EU, China GB/T30121, and the vast majority of industrial instruments worldwide, commonly known as the 385 curve, and is the mainstream standard.
2. Definition and Numerical Difference of α Temperature Coefficient
α = (R₁₀₀−R₀)/(R₀×100), representing the average resistance temperature coefficient from 0 to 100°C.
- IEC 60751: α=0.003851 ≈ 0.00385, standard resistance at 100°C is 138.51Ω, average resistance increase per °C from 0 to 100°C is 0.3851Ω.
- GOST 6651-2009: α=0.003910, standard resistance at 100°C is 139.10Ω, average resistance increase per °C from 0 to 100°C is 0.3910Ω.
3. Different Roots of Platinum Wire Purity and Graduation Polynomials
- IEC 60751 (385): Uses industrial doped platinum; to adapt to the ITS-90 international temperature scale, the pure platinum coefficient is artificially lowered, using the globally universal Callendar-Van Dusen polynomial (A=3.9083e-3, B=-5.775e-7, C=-4.183e-12).
- GOST 6651-2009 (391): Uses early high-purity undoped platinum wire, with higher platinum purity and a higher original inherent temperature coefficient; the standard uses independent graduation constants and cannot be mixed with IEC coefficients.
4. Resistance Values at the Same Temperature and Temperature Measurement Errors
Both have a resistance of 100Ω at 0°C, but the resistance values at 100°C and above are completely different. Mixing instruments will cause errors of tens of degrees. The specific comparison is shown in the table below:
| Temperature (°C) | IEC 60751 Resistance (Ω) | GOST 6651-2009 Resistance (Ω) | Resistance Difference (Ω) | Equivalent Error (°C) |
|---|---|---|---|---|
| 0 | 100.00 | 100.00 | 0 | 0 |
| 100 | 138.51 | 139.10 | 0.59 | ≈1.5 |
| 200 | 175.86 | 177.20 | 1.34 | ≈3.5 |
| 400 | 247.09 | 249.80 | 2.71 | ≈7.0 |
| 600 | 313.71 | 317.80 | 4.09 | ≈10.6 |
Simply put: A 391 probe connected to a 385 instrument will read severely high; conversely, the reading will be severely low, and they are completely non-interchangeable.
5. Application Scenarios and Associated Equipment Are Not Interchangeable
- IEC 60751 α=0.00385: Universally used in China, Europe, America, Japan, and South Korea; PLCs, temperature controllers, paperless recorders, and RTD transmitters use the IEC 385 curve by default; standard equipment for all domestic industrial temperature measurement devices.
- GOST 6651-2009 α=0.003910: Dedicated only to old equipment in Russia, Belarus, Kazakhstan, and other CIS countries, as well as Russian-made boilers, chemical, and metallurgical equipment; only Russian-system instruments support the 391 graduation curve, and ordinary domestic temperature controllers are not compatible.
6. Subtle Differences in Additional Technical Requirements of the Standards
Both have the same temperature range of -200 to +850°C and minimum measurement span of 10K, but the additional requirements differ:
- IEC 60751: Strictly specifies A/AA/B accuracy tolerance grades, self-heating, AC measurement characteristics, and insulation requirements, with globally unified quality control specifications.
- GOST 6651-2009: Adopts Russian-style testing, tolerance, and aging assessment standards, applicable only to the Russian metrology system for traceability.
Selection and Usage Recommendations
- When replacing sensors, the probe and instrument curves must match completely; 385 and 391 cannot be interchanged.
- For domestic projects and imported European/American equipment: always choose IEC 60751 (α=0.00385).
- For old Russian-system equipment and CIS-produced units: only choose GOST 6651-2009 (α=0.003910).
- If the instrument supports curve switching, you can switch between 385/391 graduations in the parameters to adapt to the corresponding probe.