# Type J Thermocouple Wire — Iron / Constantan

> Temperature range: −40 … +750 °C. Full batch-to-furnace traceability. IEC 60584-1 Class 1, ASTM E230.

**Temperature range:** −40 … +750 °C

## Alloy composition

- **Positive leg:** Iron (Fe 99.5%)
- **Negative leg:** Constantan (CuNi 55/45)
- **EMF tolerance:** ±1.5°C (0–275°C) / ±0.4% (275–750°C)

## Advantage

Higher EMF output than Type K in the 0–400°C range. Cost-effective due to iron positive leg. Good for reducing atmospheres.

## Limitation

Iron leg oxidises rapidly above 550°C. Not for oxidising atmospheres above 750°C. Not for vacuum or sulphur-containing atmospheres.

## Technical specifications

| Property | Specification |
|---|---|
| Diameter Range | φ0.025mm – φ5.0mm |
| Tolerance | ±0.005mm (fine) / ±0.02mm (standard) |
| Temperature Range | −40 … +750 °C |
| Standards | IEC 60584-1 Class 1 / ASTM E230 / DIN EN 60584 |
| Surface Finish | Bright / Oxidised / Electro-polished |
| Packaging | DIN 125 spool / Coil / Custom reel |
| Coil Weight | 5kg / 10kg / 20kg standard |
| Traceability | Furnace batch number engraved on spool |

## Available forms

| Form | Specification | Notes |
|---|---|---|
| bare-wire | Bare Wire | Solid single-strand, φ0.025–5.0 mm, bright or oxidised. |
| stranded-wire | Stranded Wire | Multi-strand for flexibility and vibration resistance. 7/19/37 strand. |