Type J Thermocouple
Iron Constantan thermocouple material for industrial equipment and replacement probes
Type J is a base-metal thermocouple type that uses Iron as the positive leg and Constantan as the negative leg. It is commonly used for moderate-temperature industrial equipment, older control systems, plastics machinery, ovens, and replacement probes where the installed instrument expects Type J input.
Thermometrics manufactures Type J thermocouple assemblies as MI cable probes, wire sensors, plug-and-lead sensors, head-style assemblies, surface sensors, and custom replacement parts built to drawing.
Common Type J RFQ details
Type J temperature range
Type J is commonly referenced for approximately 32°F to 1382°F (0°C to 750°C). The practical assembly rating depends on sheath material, insulation, atmosphere, probe diameter, junction style, and service life expectations.
Type J thermocouple material
Type J uses Iron for the positive conductor and Constantan for the negative conductor. Because the iron leg can oxidize, application atmosphere and moisture exposure should be reviewed before specifying Type J for long-term elevated-temperature service.
Type J chart PDFs
When Type J is a strong fit
When to review alternatives
Type K or Type N may be reviewed for broader high-temperature service. Type T may be reviewed for lower-temperature or moisture-prone work. Noble-metal Type R, S, or B may be reviewed for clean high-temperature furnace service.
Related thermocouple resources
Wire Sensors
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