IEC 60584-1 and ASTM E230: same EMF data, different class names.
Tolerance class equivalents
| IEC 60584-1 | ASTM E230 | Type K at 1000 °C | Type N at 1000 °C | Notes |
|---|---|---|---|---|
| Class 1 | Special Limits | ±4.0 °C | ±4.0 °C | Approx. 2× better than Class 2 |
| Class 2 | Standard Limits | ±7.5 °C | ±7.5 °C | Standard industrial grade |
| Class 3 | — | ±12.5 °C | — | IEC-only, rarely used for base metals |
How to specify dual compliance
- State both standards on the purchase order — for example “IEC 60584-1 Class 1 and ASTM E230 Special Limits”.
- Confirm the MTC will reference each standard separately, so both audiences find their own clause.
- Check the colour code against the instrument the cable will actually be connected to.
Key differences
EMF reference tables: IEC 60584-1 and ASTM E230 use the same underlying ITS-90 temperature scale. The EMF values are identical for all practical purposes (differences are below 1 µV). A wire manufactured to IEC Class 1 will meet ASTM Special Limits and vice versa.
Tolerance definition: IEC expresses tolerance as a fixed value (±X °C) in the low range and a percentage of reading (±Y%) in the high range. ASTM uses the same mathematical formula but uses different terminology: “Special Limits of Error” ≈ IEC Class 1, “Standard Limits of Error” ≈ IEC Class 2.
Testing requirements: ASTM E230 references ASTM E220 (calibration method) and ASTM E1350 (homogeneity testing). IEC references IEC 60584-2 (tolerances) and IEC 60584-3 (extension cable). The testing procedures produce equivalent results.
Dual certification: We can supply the same batch certified to both IEC 60584-1 Class 1 and ASTM E230 Special Limits. No additional testing is required — we simply issue two MTCs referencing the respective standard.
Frequently Asked Questions
Are IEC 60584-1 and ASTM E230 EMF tables the same?
For all practical purposes, yes. Both standards sit on the ITS-90 scale and the EMF values differ by less than 1 µV, so wire made to IEC Class 1 meets ASTM Special Limits and vice versa.
What is the ASTM equivalent of IEC Class 1 and Class 2?
Class 1 corresponds to ASTM Special Limits of Error and Class 2 to Standard Limits of Error. IEC Class 3 has no ASTM equivalent and is rarely used for base metals.
How much error does each class allow at 1000 °C?
For Type K at 1000 °C: ±4.0 °C for Class 1 / Special Limits and ±7.5 °C for Class 2 / Standard Limits. The same figures apply to Type N.
Do I need separate wire for IEC and ASTM certification?
No. We supply one batch certified to both IEC 60584-1 Class 1 and ASTM E230 Special Limits; no additional testing is required, we simply issue two Material Test Certificates.
Bottom line: IEC 60584-1 and ASTM E230 describe the same thermoelectric behaviour with different vocabulary: identical tolerance formulas and near-identical EMF tables, different class names and testing references. Where you ship into both regions, order one batch certified to both — it removes the risk of a mismatch between the certificate and the standard your customer audits against.