What is the advantage of assembled thermocouples over sheathed types?

Assembled thermocouples feature replaceable sensing elements that can be changed without removing the protection tube. They offer larger tube diameters for better mechanical strength and support high-alumina ceramic tubes for temperatures up to 1200 C.

What does the G suffix mean in the model number?

The G suffix indicates a variable cross-section fast response protection tube design, achieving less than 24 seconds response time compared to standard 90 seconds.

How do I choose between diameter 16 and 20 protection tubes?

Diameter 16mm is standard for most applications up to 1000mm insertion length. Diameter 20mm is recommended for longer insertions, higher flow velocities, or greater rigidity needs.

What is the maximum pressure rating?

Standard screw thread and flange types support up to 4 MPa. The fixed thread cone type (6xx) supports up to 15 MPa for high-pressure systems.

Can assembled thermocouples output 4-20mA?

Yes. Add the B suffix for integrated SBW transmitter converting thermocouple signal to 4-20mA output.

What thermocouple type should I choose?

Type K is most versatile (0-1200 C). Type N offers better high-temp stability. Type E has highest sensitivity below 800 C. Type J is economical for 0-600 C. Type T provides best accuracy for low-temp up to 350 C.

HMK Temperature Sensors

Assembled Thermocouples

Modular assembled thermocouples with replaceable spring-loaded sensing elements for easy maintenance. Available in types K, N, E, J, T with protection tube diameters Ø16 and Ø20mm. 8 mounting configurations including screw thread, flange, pipe joint, and cone types. IEC 584 Class I & II certified.

Types K/N/E/J/T 0–1200°C Range IEC 584 Class I & II Ø16/Ø20mm Tube <24s Fast Response IP55/IP65

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Why Choose Assembled Thermocouples?

Assembled thermocouples are the workhorses of industrial temperature measurement, designed for demanding environments that require modular flexibility and easy maintenance. Unlike sheathed (mineral-insulated) thermocouples, assembled types feature a pressure-spring-loaded sensing element that can be quickly replaced without removing the protection tube from the process vessel, dramatically reducing downtime during scheduled maintenance.

HMK assembled thermocouples support five thermocouple types (K, N, E, J, T) covering temperature ranges from 0°C to 1200°C. The protection tube is available in stainless steel (1Cr18Ni9Ti, 0Cr25Ni20) for standard applications, or high-alumina ceramic for temperatures exceeding 800°C. With eight distinct mounting configurations — from non-fixed and screw thread to flanged, pipe joint, and cone types — there is a solution for virtually any industrial installation scenario.

All models comply with IEC 584 and GB/T 30429-2013 standards. Standard models achieve thermal response time <90 seconds, while the fast-response G-suffix variants reduce this to under 24 seconds using a variable cross-section tube design. Waterproof (IP55) and splash-proof (IP65) junction box options ensure reliable performance in harsh environments.

Technical Specifications

Parameter	Value
Thermocouple Types	K, N, E, J, T (per IEC 584)
Temperature Range	0°C to 1200°C (type N/K max with high-alumina tube)
Tolerance Class I	±1.5°C or ±0.004\|t\| (K, N, E, J); ±0.5°C or ±0.004\|t\| (T)
Tolerance Class II	±2.5°C or ±0.0075\|t\| (K, N, E, J); ±1.0°C or ±0.0075\|t\| (T)
Protection Tube Diameter	Ø16, Ø20 mm (stainless steel); Ø16, Ø20 mm (high-alumina ceramic)
Protection Tube Material	1Cr18Ni9Ti (0–800°C), 0Cr25Ni20 (0–1100°C), High-alumina ceramic (0–1200°C)
Thermal Response Time	<90s (standard), <24s (fast-response G suffix)
Element Configuration	Single or dual element (replaceable spring-loaded)
Insulation Resistance	≥1000 MΩ (1m sample at 500V DC, 15–35°C, RH 45–75%)
Nominal Pressure	≤4 MPa (screw/flange types); ≤15 MPa (cone thread type)
Junction Box	Waterproof (IP55) or Splash-proof (IP65)
Standards	IEC 584, GB/T 30429-2013
Insertion Length	150–2150mm (customizable)

Temperature Range & Tolerance by Type

Type	Graduation	Class I		Class II
Type	Graduation	Tolerance	Range (°C)	Tolerance	Range (°C)
WRN	K	±1.5°C	-40 ~ +375	±2.5°C	-40 ~ +333
WRN	K	±0.004\|t\|	375 ~ 1000	±0.0075\|t\|	333 ~ 1200
WRM	N	±1.5°C	-40 ~ +375	±2.5°C	-40 ~ +333
WRM	N	±0.004\|t\|	375 ~ 1000	±0.0075\|t\|	333 ~ 1200
WRE	E	±1.5°C	-40 ~ +375	±2.5°C	-40 ~ +333
WRE	E	±0.004\|t\|	375 ~ 800	±0.0075\|t\|	333 ~ 900
WRF	J	±1.5°C	-40 ~ +375	±2.5°C	-40 ~ +333
WRF	J	±0.004\|t\|	375 ~ 750	±0.0075\|t\|	333 ~ 750
WRC	T	±0.5°C	-40 ~ +125	±1.0°C	-40 ~ +133
WRC	T	±0.004\|t\|	125 ~ 350	±0.0075\|t\|	133 ~ 350

Assembled Thermocouples junction box type

Selection Guide by Installation Type

Choose the appropriate mounting configuration based on your process connection requirements, pressure rating, and installation constraints. The table below compares all 8 installation types to help you select the right model series.

Installation Type	Series Code	Connection	Tube Φ	Pressure	Best For
1. Non-Fixed	1xx	None (friction fit)	Ø16/Ø20	—	Open vessels, temporary measurement
2. Fixed Screw Thread	2xx	M27×2 / G3/4	Ø16/Ø20	≤4 MPa	Standard pipe/vessel installations
3. Movable Flange	3xx	Adjustable flange	Ø16/Ø20	≤4 MPa	Vessels needing adjustable depth
4. Fixed Flange	4xx	Welded flange	Ø16/Ø20	≤4 MPa	Permanent high-pressure installations
5. Adjustable Pipe Joint	5x	M20×1.5 / NPT1/2	Ø3–Ø8	—	Small bore, adjustable depth
6. Fixed Thread Cone	6xx	M33×2 / NPT1	Ø15	≤15 MPa	High-pressure fluid systems
7. Straight Pipe Joint	7x	M20×1.5 / NPT1/2	Ø3–Ø8	—	Straight pipe penetrations
8. Fixed Threaded Pipe	8x	M20×1.5 / NPT1/2	Ø3–Ø8	—	Permanent pipeline monitoring

Non-Fixed Assembly Thermocouples (1xx Series)

High-alumina ceramic protection tubes for temperatures up to 1200°C. Available in both anti-spray (IP65) and waterproof (IP55) junction boxes.

Model	Type	Range (°C)	Response	Tube Material	Ø (mm)	IP Rating
WRM-122 / WRN-122	N / K	0–1200	<240s	High-alumina	Ø16	IP65
WRM-123 / WRN-123	N / K	0–1200			Ø20	IP65
WRM-132 / WRN-132	N / K	0–1200			Ø16	IP55
WRM-133 / WRN-133	N / K	0–1200			Ø20	IP55

Insertion lengths (L): 300×150 to 2150×2000 mm. Both single and dual element configurations available.

Fixed Screw Thread Thermocouples (2xx Series)

Most widely used configuration. M27×2 or G3/4 thread connection. Available in all five thermocouple types with standard or fast-response (G suffix) protection tubes.

Model	Type	Range (°C)	Response	Tube Material	Ø (mm)
WRM-230 / WRM-230G	N	0–800 / 0–1100	<90s / <24s	1Cr18Ni9Ti / 0Cr25Ni20	Ø16
WRN-230 / WRN-230G	K	0–800 / 0–1100	<90s / <24s	1Cr18Ni9Ti / 0Cr25Ni20
WRE-230 / WRE-230G	E	0–800	<90s / <24s	1Cr18Ni9Ti
WRC-230 / WRC-230G	T	0–350	<90s / <24s	1Cr18Ni9Ti
WRF-230 / WRF-230G	J	0–600	<90s / <24s	1Cr18Ni9Ti
Ø20mm variants: WRM-231/231G, WRN-231/231G, WRE-231/231G, WRC-231/231G, WRF-231/231G — Same specs, Ø20mm tube, response <120s (std) / <24s (G)					Ø20

IP55 waterproof (230/231 series). IP65 splash-proof variants: 220/221 series with same specifications. Thread: M27×2 (standard) or G3/4 (suffix A). Nominal pressure: ≤4 MPa. Insertion lengths: 150–2150 mm.

Flange Mount Thermocouples (3xx / 4xx Series)

Movable (3xx) and fixed (4xx) flange configurations. Both support five thermocouple types with Ø16/Ø20mm protection tubes. Nominal pressure ≤4 MPa.

Configuration	Models (Ø16)	Models (Ø20)	Response (Std / Fast)	IP Rating	Lengths (mm)
Movable Flange	WR_-330 / 330G	WR_-331 / 331G	<90s / <24s	IP55	150–2150
Fixed Flange	WR_-430 / 430G	WR_-431 / 431G	<90s / <24s	IP55	150–2150

Fixed flange specifications: Ø16 flange D=Ø95, D1=Ø65, H=14mm; Ø20 flange D=Ø95(Ø105), D1=Ø65(Ø75), H=14(16)mm. Custom flanges available on request. IP65 anti-spray variants: 320/321 (movable) and 420/421 (fixed).

Cone Thread & Pipe Joint Thermocouples (5x/6xx/7x Series)

Specialized mounting configurations for high-pressure systems and small-bore applications.

Type	Series	Connection	Tube Ø (mm)	Max Pressure	Lengths (mm)
Fixed Thread Cone	620/630	M33×2 / NPT1	Ø15	≤15 MPa	300×150 – 650×500
Adjustable Pipe Joint	53/53A	M20×1.5 / NPT1/2	Ø3, Ø4, Ø5, Ø6, Ø8	—	245–1149
Straight Pipe Joint	73/73A	M20×1.5 / NPT1/2	Ø3, Ø4, Ø5, Ø6, Ø8	—	245–1149

Pipe joint types: Protection tube materials 0Cr25Ni20 (N/K) and 1Cr18Ni9Ti (all types). Insertion depth should match thermowell U-tube dimension. Cone thread types: 620/620G = IP65, 630/630G = IP55.

Model Numbering & Ordering Guide

The model designation follows a systematic coding system. Specify each position to define your exact requirements.

Position	Description	Options
W	Product type	W = Temperature instrument
R	Sensor type	R = Thermocouple
3rd	TC material	N = NiCr-NiSi (Type K) \| M = NiCrSi-NiSi (Type N) \| E = NiCr-CuNi (Type E) \| C = Cu-CuNi (Type T) \| F = Fe-CuNi (Type J)
4th	Element count	(none) = Single element \| 2 = Dual element
5th	Mounting type	1=Non-fixed \| 2=Screw thread \| 3=Movable flange \| 4=Fixed flange \| 5=Pipe joint \| 6=Thread cone \| 7=Straight pipe \| 8=Fixed pipe
6th	Junction box	2 = Anti-spray (IP65) \| 3 = Waterproof (IP55)
7th	Tube diameter	0 = Ø16 std \| 1 = Ø20 std \| 2 = Ø16 high-alumina \| 3 = Ø20 high-alumina
Suffix	Additional	G = Fast response (variable cross-section) \| B = With SBW temperature transmitter \| A = BSP/NPT thread option

Example: WRN-231G = Type K thermocouple, single element, fixed screw thread mount, waterproof junction box (IP55), Ø20mm standard tube, fast response. Specify insertion length L separately (e.g., L=300mm).

Key Features

Replaceable Sensing Element

Pressure spring-loaded design allows quick element replacement without removing the protection tube from the process. Reduces maintenance time from hours to minutes, cutting downtime costs.

8 Mounting Configurations

From non-fixed and screw thread to flanged, pipe joint, and cone types. Comprehensive mounting portfolio ensures compatibility with any process connection standard.

Fast Response Option (G Suffix)

Variable cross-section protection tube reduces thermal mass at the tip, achieving <24s response time compared to <90s standard. Available across all thermocouple types and mounting configs.

Wide Temperature Range

Covering 0°C to 1200°C with five thermocouple types. High-alumina ceramic tubes extend range beyond 800°C where stainless steel tubes reach their limits.

IEC 584 Class I & II Certified

Full compliance with international thermocouple standards. Class I tolerance as tight as ±0.5°C (Type T) ensures precision in critical process control applications.

Dual Element Configuration

Optional dual-element setup provides redundant measurement for safety-critical applications. Both elements housed in a single protection tube, saving nozzle space on vessels.

Industry Applications

Petrochemical & Refining

Reactor temperature monitoring, distillation column drums, cracking furnace control, and feed stream preheating. Fixed screw thread (2xx) and flange (3xx/4xx) mounts handle high-pressure process connections.

Power Generation

Boiler drum temperature, superheater outlet monitoring, economizer efficiency control, and steam quality assurance. Fast-response G-suffix models ensure rapid detection of temperature excursions.

Steel & Metallurgy

Reheating furnace zones, soaking pit temperature, rolling mill process control, and quenching tank monitoring. High-alumina ceramic tubes (1xx series) withstand temperatures up to 1200°C.

Cement & Building Materials

Rotary kiln temperature profiles, preheater tower zones, clinker cooler monitoring, and calcination process control. Non-fixed (1xx) configuration allows easy repositioning during maintenance.

Food & Pharmaceutical

Autoclave sterilization, pasteurization temperature, drying process optimization, and cooking vessel monitoring. Pipe joint types (5x/7x) with small Ø3–Ø8mm tubes fit standard sanitary fittings.

HVAC & Environmental

Large duct temperature measurement, stack gas monitoring, ambient air quality control, and heat recovery optimization. Multiple insertion lengths from 150mm to 2150mm cover any duct diameter.

Explosion-Proof Thermocouples

NEPSI-certified dII BT4/CT5 explosion-proof thermocouples for hazardous environments. Flameproof enclosure with Type K/N/E/J/T elements.

Sheathed Thermocouples

Mineral-insulated metal-sheathed (MIMS) thermocouples for high-temperature, fast-response, and compact installations.

SBW Temperature Transmitter

4-20mA/HART output head-mounted transmitters for thermocouple and RTD signal conditioning.

Frequently Asked Questions

Assembled thermocouples feature replaceable spring-loaded sensing elements that can be changed without removing the protection tube. This reduces maintenance time significantly. They also offer larger protection tube diameters (Ø16/Ø20mm) for better mechanical strength in high-pressure applications, and support high-alumina ceramic tubes for temperatures up to 1200°C.

The G suffix indicates a variable cross-section (fast response) protection tube. Standard models have response time <90 seconds, while G-suffix models achieve <24 seconds by tapering the protection tube near the sensing tip to reduce thermal mass. The G option is available across all thermocouple types and mounting configurations.

Ø16mm tubes are standard for most applications with insertion lengths up to approximately 1000mm. Choose Ø20mm for longer insertion lengths (>1000mm), higher flow velocities, or when greater mechanical rigidity is needed. High-alumina ceramic versions of both sizes are available for temperatures above 800°C.

Standard screw thread (2xx), movable flange (3xx), and fixed flange (4xx) types are rated for ≤4 MPa nominal pressure. The fixed thread cone type (6xx) supports up to 15 MPa, making it suitable for high-pressure fluid systems. Pipe joint types (5x/7x) are designed for lower-pressure installations.

Yes. Add the “B” suffix to any model to include an integrated SBW head-mounted temperature transmitter in the junction box. This converts the thermocouple mV signal to a standard 4-20mA output for direct PLC/DCS connection. Alternatively, any assembled thermocouple can be paired with a separate SBW transmitter.

Type K (WRN) is the most versatile, covering 0–1200°C with good linearity. Type N (WRM) offers better stability at high temperatures and less drift. Type E (WRE) has the highest sensitivity for precise measurements below 800°C. Type J (WRF) is economical for 0–600°C. Type T (WRC) provides the best accuracy (±0.5°C Class I) for low-temperature applications up to 350°C.

Need a Custom Assembled Thermocouple?

Our engineering team specializes in thermocouple solutions tailored to your exact process requirements. Contact us for custom tube materials, non-standard insertion lengths, special flange dimensions, high-volume pricing, or integrated transmitter configurations.

Our engineers typically respond within 12 business hours with detailed technical specifications and pricing.

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Need to Convert Millivolts to Temperature?

If your assembled thermocouple reads in mV but your DCS expects °C — or vice-versa — our free engineering calculator handles all eight IEC 60584 types with manual or automatic cold-junction compensation, complete with CSV export for calibration records.

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