Thermocouple selection
Type J vs Type K Thermocouples: What to Compare Before Choosing
Type J uses an iron versus copper-nickel alloy pair, while Type K uses nickel-chromium versus nickel-aluminium alloys. Type K has the wider NIST reference-data range, but the complete assembly and installation still determine the usable operating limit.
Technical reference
Type J and Type K at a Glance
The values below come from the NIST Temperature Scale Database (SRD 60). They describe thermocouple reference data, not a guaranteed operating range for every probe, cable or complete assembly.
| Reference characteristic | Type J | Type K |
|---|---|---|
| Thermoelement composition | Iron versus a copper-nickel alloy | Nickel-chromium alloy versus nickel-aluminium alloy |
| NIST reference-data range | -210°C to 1200°C | -270°C to 1372°C |
| What the value means | A reference-table range for the thermocouple type. It is not the operating limit of a specific Yog Electro assembly. | |
Do not use the reference range as the product rating
The practical limit must be checked against the selected sheath, insulation, junction, diameter, cable, termination, process atmosphere, mounting and receiving instrument. Confirm the complete construction for the actual measurement point.
Selection FAQs
Type J vs Type K: Practical Answers
Which products list Type J or K?
The current listings show J/K as selectable on MI-37 and the PTFE assembly, while Catcon lists K type only and ties it to supported automotive and CNG testing.
What should I compare?
Start with the receiving instrument and measurement point, then match process conditions, junction, sheath, diameter, mounting, cable and termination to a single assembly's listed options.
What reference ranges does NIST publish for Type J and Type K?
NIST SRD 60 lists reference-data ranges of -210°C to 1200°C for Type J and -270°C to 1372°C for Type K. These are reference-table ranges, not guaranteed operating limits for a finished sensor assembly.
Product options
What Current Product Listings Show
The listings below show where J and K are offered in the current catalogue. They do not define a single temperature range or establish suitability for every installation.
| Product | Type J | Type K | Other documented choices |
|---|---|---|---|
| Mineral Insulated Thermocouple | Selectable | Selectable | Grounded or ungrounded junction; listed sheath, diameter and cable options. |
| Special Coated (PTFE) Thermocouple | Selectable | Selectable | Simplex or duplex; ceramic or mineral insulation; ungrounded junction; listed sheath and termination options. |
| Catcon Thermocouple | Not listed | Listed | Ungrounded junction, SS304 or SS316 sheath, and a documented cable construction for supported automotive testing applications. |
Decision boundary
Do Not Choose from the Letter Alone
Where a product offers both J and K, the catalogue confirms availability, not which calibration fits every process. The selected calibration must also match the receiving instrument and the complete measurement requirement.
Construction choices are product-specific. Do not transfer a junction, sheath, cable, diameter, insulation or termination option from one assembly to another unless it is listed for the selected product.
Details to Share for Selection
- Process conditionsNormal and maximum temperature, process medium or atmosphere, cycling and vibration.
- Measurement pointSurface, immersion, furnace, machinery or test location and what the reading controls or protects.
- Mechanical assemblyRequired sheath material, diameter, insertion length, mounting and available space.
- Electrical interfaceJunction, simplex or duplex requirement, cable route, termination and receiving-instrument input.
A practical route
Prepare a Complete Enquiry
- 01
Check the instrument
Identify the thermocouple input required by the existing or proposed receiving instrument.
- 02
Define the complete point
List the process, sensing location, construction, mounting, cable route and access constraints.
- 03
Match one product
Use only the options listed for that assembly and contact the engineering team about any unresolved details.
Need a Type J or Type K Review?
Share the process conditions, measurement point, construction, mounting, cable route and instrument input.