Type J Bare Wire
Iron / Constantan
Solid single-strand thermocouple wire. φ0.025mm ultra-fine to φ5.0mm standard. Bright or oxidized finish.
Type J Bare Wire: φ0.025mm – φ5.0mm, −40°C to +750°C, IEC 60584-1 Class 1
- Ø range
- φ0.025mm – φ5.0mm
- Temp
- −40°C to +750°C
- EMF tol.
- ±1.5°C (0–275°C) / ±0.4% (275–750°C)
- Testing
- 100%
Technical Specifications
Type J Bare Wire — Iron / Constantan at −40°C to +750°C, solid single strand from φ0.025mm – φ5.0mm, supplied to IEC 60584-1 Class 1.
| Property | Specification |
|---|---|
| Positive Leg | Iron (Fe 99.5%) |
| Negative Leg | Constantan (CuNi 55/45) |
| Temperature Range | −40°C to +750°C |
| Diameter Range | φ0.025mm – φ5.0mm |
| Diameter Tolerance | ±0.005mm (fine) / ±0.02mm (standard) |
| EMF Tolerance | ±1.5°C (0–275°C) / ±0.4% (275–750°C) |
| Standards | IEC 60584-1 Class 1 / ASTM E230 / DIN EN 60584 |
| Surface Finish | Bright / Oxidized / Electro-polished |
| Condition | Hard (cold-drawn) / Soft (annealed) / Bright finished |
| Packaging | DIN 125 spool / Coil / Custom reel |
| Coil Weight | 5kg / 10kg / 20kg standard |
| Testing & Traceability | 100% eddy-current + resistance + dimensional · MTC · EMF calibration certificate · Furnace batch traceability |
How to specify Type J Bare Wire
- Confirm the alloy for your operating temperature — Iron / Constantan, rated −40°C to +750°C in air.
- Pick the conductor diameter from φ0.025mm – φ5.0mm (diameter tolerance ±0.005mm (fine) / ±0.02mm (standard)) — solid single-strand Iron / Constantan at the ultra-fine end of the −40°C to +750°C range.
- Choose the temper condition for this J · Iron / Constantan wire — Hard (cold-drawn) / Soft (annealed) / Bright finished. The temper is chosen for the solid J sensing element held in the furnace or panel.
- Choose the surface finish for J · Iron / Constantan — Bright / Oxidized / Electro-polished. Finish is selected for the atmosphere the J element will sit in.
- Choose the packaging — DIN 125 spool / Coil / Custom reel, standard coil weights 5kg / 10kg / 20kg standard. Spooled to protect the J solid conductor in transit and handling.
- Quote Type J Bare Wire against IEC 60584-1 Class 1 and request the MTC / EMF calibration certificate with the batch number for traceability.
Which thermocouple type fits the job
These are the J-type ranges as they apply to the solid single-strand form described on this page. Confirm the type first, then pick the conductor diameter.
| Type | Alloy | Range | EMF tolerance |
|---|---|---|---|
| E | Chromel / Constantan | −200 … +900 °C | ±1.5°C (0–275°C) / ±0.4% (275–900°C) |
| J this page | Iron / Constantan | −40 … +750 °C | ±1.5°C (0–275°C) / ±0.4% (275–750°C) |
| K | Chromel / Alumel | −200 … +1370 °C | ±1.5°C (0–375°C) / ±0.4% (375–1000°C) |
Verification & quality evidence
- IEC 60584-1 Class 1 / ASTM E230 / DIN EN 60584
- 100% eddy-current + resistance + dimensional · MTC · EMF calibration certificate · Furnace batch traceability
- Third-party testimonials and site references are being collected for this product line — ask for Type J Bare Wire reference contacts in comparable static installations when you request a quote.
Frequently Asked Questions
What alloy is Type J bare wire made from?
Iron (Fe 99.5%) for the positive leg and Constantan (CuNi 55/45) for the negative leg.
What temperature range does Type J cover?
−40 °C to +750 °C. The iron leg oxidises rapidly above 550 °C, so the upper limit applies only in suitable atmospheres.
Can Type J be used in oxidising, vacuum or sulphur-containing atmospheres?
No. Type J suits reducing atmospheres and is commonly used in plastics, food and HVAC work. It is not for oxidising service above 750 °C, nor for vacuum or sulphur-bearing atmospheres.
Bottom line: Type J Bare Wire (Iron / Constantan) covers −40°C to +750°C across φ0.025mm – φ5.0mm, with EMF tolerance ±1.5°C (0–275°C) / ±0.4% (275–750°C). Supplied to IEC 60584-1 Class 1 with 100% EMF testing, MTC and furnace batch traceability.