Image Gallery (1/1)
Type keywords to search pages, products, standards and articles
As defined in GB/T 18404-2022, a mineral-insulated (MI) thermocouple consists of thermocouple wires, a high-purity magnesium oxide insulation layer and a metal protection tube that are compacted into a solid composite structure through multiple integrated drawing passes. It is used with various indicating instruments, recording devices and temperature control systems to measure the temperature of fluids, steam, gaseous media and solid surfaces. It is widely used in core industrial sectors such as petrochemical, power generation, iron and steel metallurgy, precision manufacturing, semiconductors and aerospace, and is also an indispensable basic temperature sensing element in scientific experiments and high-end equipment testing.
Tel: 0512-57892201 Mobile: 13451695112
| Code Segment | Meaning & Options | Value in This Example |
|---|---|---|
| W | Temperature instrument | W |
| R | Thermocouple | R |
| N | Thermocouple Graduation （P: PtRh10-Pt (S)，Q: PtRh13-Pt (R)，R: PtRh30-PtRh6 (B)，N: NiCrSi-NiSi (N)，M: NiCrSi-NiSiMg (N)，E: NiCr-CuNi (E)，F: Fe-CuNi (J)，C: Cu-CuNi (T)） | N NiCrSi-NiSi (N) |
| K | Sheath Type | K, MI |
| ₂ | No. of Thermocouples （Single (unmarked)，2: Dual element） | ₂ Dual element |
| 2 | Terminal Head Type （0 Simplified，2 Splash-proof，3 Waterproof，4 Flameproof (Ex d)，6 Round plug-in，7 Flat plug-in，8 Handle type，9 With extension wire） | 2 Splash-proof |
| 4 | Mounting Type （1 Without fixing device，2 Fixed compression thread，3 Movable compression thread，4 Fixed compression flange，5 Movable compression flange） | 4 Fixed compression thread |
| 1 | Hot Junction Type （1 Insulated，2 Grounded (shell-contact)，3 Split-core insulated，4 Exposed） | 1 Insulated |
| Ⅱ | Tolerance Class （Ⅰ: Class I，Ⅱ: Class II，Ⅲ: Class III，Pt: Class Pt） | Class II |
| Ø6×600 | Sheath O.D. × Length （Ø0.5 ~ Ø8.0） | Ø6mm × 600mm |
| G39 | Protection Tube Material (1Cr18Ni9Ti is indicated by B， GH3039 by G39， GH3030 by G30， 304， 316L， 2520) | G39（GH3039） |
| Product name | Model | Graduation No. | Outer Sheath Material | Outer Dia. (mm) | Recommended max. service temperature °C |
| MI NiCr-NiSi (Type K) thermocouple MI NiCrSi-NiSiMg (Type N) thermocouple |
WRNK WRMK |
K N |
GH3030 GH3039 Cr25Ni20 |
0.5，1.0 | 500 |
| 1.5，2.0 | 800 | ||||
| 3.0，4.0，4.5，5.0 | 900 | ||||
| 6.0，8.0 | 1100 | ||||
| MI NiCr-NiSi (Type K) thermocouple MI NiCrSi-NiSiMg (Type N) thermocouple |
WRNK WRMK |
K N |
1Cr18Ni9Ti 316L 304 |
0.5，1.0 | 400 |
| 1.5，2.0 | 600 | ||||
| 3.0，4.0，4.5，5.0 | 800 | ||||
| MI NiCr-CuNi (constantan) thermocouple | WREK | E | 1Cr18Ni9Ti 316L 304 |
0.5，1.0 | 400 |
| 1.5，2.0 | 500 | ||||
| 3.0，4.0，4.5，5.0 | 600 | ||||
| 6.0，8.0 | 800 | ||||
| MI Fe-CuNi (constantan) thermocouple | WRFK | J | 1Cr18Ni9Ti 316L 304 |
0.5，1.0 | 300 |
| 1.5，2.0 | 400 | ||||
| 3.0，4.0，4.5，5.0 | 500 | ||||
| 6.0，8.0 | 750 | ||||
| MI Cu-CuNi (constantan) thermocouple | WRCK | T | 1Cr18Ni9Ti 316L 304 |
0.5，1.0 | 200 |
| 1.5，2.0，3.0 | 300 | ||||
| 6.0，8.0 | 400 | ||||
| MI PtRh10-Pt thermocouple | WRPK | S | GH3030 GH3039 N10276 |
1.0，1.5 | 800 |
| 2.0，3.0 | 900 | ||||
| 4.0，4.5 | 1000 | ||||
| 5.0，6.0，8.0 | 1300 | ||||
| MI PtRh13-Pt thermocouple | WRQK | R | GH3030 GH3039 N10276 |
1.0，1.5 | 800 |
| 2.0，3.0 | 900 | ||||
| 4.0，4.5 | 1000 | ||||
| 5.0，6.0，8.0 | 1300 | ||||
| MI PtRh30-PtRh6 thermocouple | WRRK | B | GH3030 GH3039 N10276 |
4.0，4.5 | 1100 |
| 5.0，6.0，8.0 | 1300 |
Remarks:
1. For Types S, R and B MI platinum-rhodium thermocouples, the maximum service temperature of the N10276 (Hastelloy C276) protection tube is 1300 °C;
2. Products of other materials and outer diameters can be supplied by agreement between supplier and purchaser;
3. All MI thermocouples comply with GB/T 18404-2001.
With the reference junction at 0 °C, the thermoelectric EMF shall comply with GB/T 16839.1—1997 “Thermocouples — Part 1: Reference tables”, and the tolerances for different classes shall comply with the values given in the table below.
| Tolerance Class | Model | Graduation No. | Tolerance value℃ | Temperature range °C | |
| Base-metal MI thermocouple | I | WRNK | K | ±1.5℃or±0.4%t | -40～1100 |
| WRMK | N | ||||
| WREK | E | -40～800 | |||
| WRFK | J | -40～750 | |||
| WRCK | T | ±0.5℃or±0.4%t | -40～350 | ||
| Ⅱ | WRNK | K | ±2.5℃or±0.75%t | -40～1100 | |
| WRMK | N | ||||
| WREK | E | -40～800 | |||
| WRFK | J | -40～750 | |||
| WRCK | T | ±1.0℃or±0.75%t | -40～400 | ||
| Ⅲ | WRNK | K | ±2.5℃or±1.5%t | -200～40 | |
| WRMK | N | ||||
| WREK | E | ||||
| WRCK | T | ±1.0℃or±1.5%t | |||
| Noble-metal MI thermocouple | Ⅱ | WRPK | S | ±1.5℃or±0.25%t | 300～1100 |
| WRQK | R | ||||
| Pt | WRPK | S | ±3.0℃or±0.5%t | ||
| WRQK | R | ||||
| Ⅱ | WRRK | B | ±0.25%t | 600～1200 | |
| Ⅲ | ±4.0℃or±0.5%t | ||||
Remarks: In the table, t is the absolute value of the measured temperature and Pt is the standard class.
| Hot Junction Type | Outer Dia. (mm) | ||||||||
| 0.5 | 1.0 | 1.5 | 2.0 | 3.0 | 4.0 | 5.0 | 6.0 | 8.0 | |
| Insulatedτ0.63s | 0.1 | 0.2 | 0.3 | 0.5 | 1.5 | 3.0 | 5.0 | 8.0 | 10 |
| Grounded (shell-contact)τ0.63s | 0.05 | 0.1 | 0.2 | 0.3 | 0.5 | 1.0 | 2.0 | 2.5 | 5.0 |
| Exposedτ0.63s | 0.01 | 0.02 | 0.02 | 0.03 | 0.05 | 0.07 | 0.08 | 0.10 | 0.12 |
| Hot Junction Type | Structure | Features |
| Insulated | Slow thermal response, high mechanical strength, long service life and resistance to electromagnetic interference | |
| By case type | Fast thermal response, high mechanical strength and long service life， not suitable for temperature measurement in locations with electromagnetic interference | |
| Separated insulated | Same as insulated type | |
| Exposed | Fastest thermal response, low mechanical strength, short service life |
The insulation resistance shall be measured between thermocouple wires, and between the wires and the sheath. For cables with an outside diameter of 1.5 mm or less, the test voltage is 75 ± 25 V DC; for cables with an outside diameter greater than 1.5 mm, the test voltage is 500 ± 50 V DC. The insulation resistance per metre at room temperature and at high temperature shall comply with the values given in the table below.
| Test environment | Model | Min. measuring length (m) | Test temperature °C | Min. insulation resistance MΩ/m |
| Room temperature | WRNK/WRMK/WREK/WRFK/WRCK /WRPK/WRQK/WRRK |
1 | 25±15 | 1000 |
| High temperature | 0.5 | 500±15 | 5 | |
| WRCK | 300±15 | 500 |
Note: The insulation material of MI thermocouples and MI thermocouple cables has limited conductivity. The insulation resistance decreases as the cable length increases; the conductivity per unit length is expressed in S·m⁻¹ (equal to Ω⁻¹·m⁻¹). For cables or thermocouples longer than 1 m, the insulation resistance is expressed in Ω·m or MΩ·m; the insulation resistance is inversely proportional to the length, and for lengths below 1 m it is expressed in MΩ·m.
For selection guidance, specification confirmation or quotation, please call 0512-57892201, Mobile 13451695112, or submit an online order. Suzhou Dingluxuan Sensor Technology Co., Ltd. provides a complete matching service from temperature sensing elements to complementary ceramic insulation parts.
To order this product or get selection guidance, please call +86 512-57892201 or submit an online order.