Thermocouple Type Comparison

Type J, K, T, E, N, R, S, B thermocouples: temperature range, accuracy, typical services, and sheath material selection.

TC Types

Thermocouple Type Comparison Reference · Rev 1 — 2026-04-16 | Per ASTM E230, IEC 60584, ISA MC96.1

Type	Conductor Materials	Range (°F)	Range (°C)	Accuracy Class 1	Sensitivity (µV/°F)	Best Applications	Limitations
J	Iron / Constantan	-346 to 1382	-210 to 750	±1.5°C or ±0.4%	30.0	General purpose, reducing atmospheres, vacuum. Common in plastics/rubber industry	Oxidizes above 1000°F; not for oxidizing or sulfur-bearing atmospheres above 500°C
K	Chromel / Alumel	-328 to 2282	-200 to 1250	±1.5°C or ±0.4%	22.0	Most widely used. Refinery, chemical, power generation. Good in oxidizing atmospheres	Green rot (Cr depletion) in reducing atmospheres 1500-1850°F. Not for vacuum or sulfur
T	Copper / Constantan	-328 to 662	-200 to 350	±0.5°C or ±0.4%	23.0	Cryogenic and low-temp. Food industry. Moisture-resistant	Limited to 662°F max. Copper oxidizes at higher temps
E	Chromel / Constantan	-328 to 1652	-200 to 900	±1.5°C or ±0.4%	40.0	Highest sensitivity of standard types. Good for low-level temp measurement	Not for reducing or vacuum. Shares K-type green rot issue at elevated temps
N	Nicrosil / Nisil	-328 to 2282	-200 to 1250	±1.5°C or ±0.4%	15.5	Replacement for K in high-temp oxidizing. Better long-term stability & drift resistance	Higher cost than K. Lower sensitivity. Newer, less historical data in some processes
R	Pt-13%Rh / Pt	32 to 2642	0 to 1450	±1.0°C or ±0.25%	3.5	High-temp precision. Glass, ceramics, semiconductor. Laboratory reference	Very expensive. Low output requires good signal conditioning. Contamination sensitive
S	Pt-10%Rh / Pt	32 to 2642	0 to 1450	±1.0°C or ±0.25%	3.2	Similar to R. Historically used as ITS-90 reference standard	Same as R. Slightly lower sensitivity than R. Being phased out by R in new designs
B	Pt-30%Rh / Pt-6%Rh	32 to 3092	0 to 1700	±0.5% above 600°C	1.8	Highest temp range. Fired heater tubes, high-temp furnaces, glass melting	Very low output below 600°F — essentially useless below 500°F. Extremely expensive
Wire Color Codes (ANSI MC96.1 / ASTM E230)
Type	(+) Wire Color	(-) Wire Color	Jacket Color	Extension Wire
J	White	Red	Brown	JX
K	Yellow	Red	Brown	KX
T	Blue	Red	Brown	TX
E	Purple	Red	Brown	EX
N	Orange	Red	Brown	NX
R	Black	Red	Green	RX (Cu-based)
S	Black	Red	Green	SX (Cu-based)
B	Gray	Red	Gray	BX (Cu-based)
REFERENCES
ASTM E230/E230M — Standard Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
IEC 60584-1 — Thermocouples Part 1: EMF Specifications and Tolerances
ISA MC96.1 (ANSI) — Temperature Measurement Thermocouples
ASTM E608 — Standard Specification for Mineral-Insulated, Metal-Sheathed Base-Metal Thermocouples

Source: Thermocouple_Type_Comparison_v1.xlsx

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