| Type | Positive/Negative Materials | Temperature Range | Features | Typical Applications |
|---|---|---|---|---|
| Type K | Nickel-Chromium (Ni-Cr) / Nickel-Aluminum (Ni-Al) | -200°C to +1260°C | • Best cost-performance ratio • Strong oxidation resistance • Good linearity |
Industrial furnaces, heat treatment, food processing |
| Type J | Iron (Fe) / Copper-Nickel (Cu-Ni) | -210°C to +760°C | • High sensitivity (~50μV/°C) • Only for reducing environments (iron oxidizes easily) |
Vacuum systems, cryogenic measurements |
| Type T | Copper (Cu) / Copper-Nickel (Cu-Ni) | -270°C to +400°C | • Best ultra-low temperature performance • Excellent corrosion resistance |
Freezing equipment, medical cryostorage |
| Type E | Nickel-Chromium (Ni-Cr) / Copper-Nickel (Cu-Ni) | -270°C to +870°C | • Highest sensitivity (~68μV/°C) • Ideal for weak signal detection |
Aerospace, scientific research |
| Type N | Nickel-Chromium-Silicon (Ni-Cr-Si) / Nickel-Silicon (Ni-Si) | -270°C to +1300°C | • Improved version of Type K • Better high-temperature stability • Superior resistance to "Green Rot" corrosion |
Automotive exhaust, high-temp heat treatment |
| Type | Positive/Negative Materials | Temperature Range | Features | Typical Applications |
|---|---|---|---|---|
| Type S | Platinum-Rhodium 10% (Pt-Rh10) / Platinum (Pt) | 0°C to +1480°C | • Highest accuracy (±0.5°C) • Extremely expensive • Requires protective sheath |
Laboratory standards, glass melting furnaces |
| Type R | Platinum-Rhodium 13% (Pt-Rh13) / Platinum (Pt) | 0°C to +1480°C | • Similar to Type S but slightly more sensitive • Weaker resistance to reducing gases |
High-temp industrial process control |
| Type B | Platinum-Rhodium 30% (Pt-Rh30) / Platinum-Rhodium 6% (Pt-Rh6) | +200°C to +1820°C | • Highest measurable temperature • Severe non-linearity at low temps • Virtually no cold junction compensation needed |
Molten steel measurement, ceramic sintering |
| Type | Features | Applications |
|---|---|---|
| Tungsten-Rhenium (W-Re) | • Measures up to 2300°C • Only usable in inert/vacuum environments (prone to oxidation) |
Rocket engines, nuclear reactors |
| Sheathed Thermocouples | • Metal sheath protects against corrosion/mechanical damage • Flexible installation |
Chemical pipelines, mobile equipment monitoring |
| Surface Thermocouples | • Flat probe design • Fast response |
Roller temperature, electronic component testing |
| Parameter | Type K | Type S | Type T | Type E |
|---|---|---|---|---|
| Sensitivity (μV/°C) | 41 | 10 | 43 | 68 |
| Long-Term Stability | Medium | Extremely High | High | Medium |
| Cost | $ | $$$$$ | $$ | $$$ |
graph TD A[Temperature >1300°C?] -->|Yes| B[Choose noble metal (S/R/B)] A -->|No| C{Ultra-high precision needed?} C -->|Yes| D[Choose Type S or RTD] C -->|No| E{Oxidizing environment?} E -->|Yes| F[Choose Type K/N] E -->|No| G{High sensitivity needed?} G -->|Yes| H[Choose Type E] G -->|No| I[Choose Type K (default choice)]
Cold Junction Compensation: Required for all types except Type B (use ICs like MAX31855).
Matching Wires: Must use corresponding compensation cables (e.g., KX for Type K).
Protective Sheaths: Required for high-temp/corrosive environments (alumina or silicon carbide).
Tip: Type K suits 90% of industrial applications; consider other types only for special requirements.
