Type N | GUILCOR SENSORS

Type N
Temperature sensors

Hello, could you advise me on the best ducting for continuous use between 200°C and 800°C?

Maximum precision
+/- 1,5°K

Minimum temperature
-200°C

Maximum temperature
+1280°C

Minimum dimensions
0,25 x 25 x 2

Response time
High

Internal Resistance
Medium

Linearity
High

Price
Medium

What is a Type N thermocouple ?

The type N thermocouple is a direct evolution of the type K, designed to address its weaknesses at high temperatures.

It combines Nicrosil (Ni-Cr-Si) and Nisil (Ni-Si), two nickel alloys reinforced with silicon to resist oxidation and thermochemical drift.

This sensor is ideal for environments where long-term stability and corrosion resistance are priorities.

It is increasingly used in the chemical, energy, and aerospace industries.

Operating principle

Like other thermocouples, type N relies on the Seebeck effect: a voltage proportional to the temperature difference is generated between the hot junction and the cold junction.

E = Sn × (T_hot - T_cold)

For type N:

S ≈ 39 µV/°C around 0 °C

Its stability and resistance to contamination make its voltage/temperature curve more consistent than that of type K over the long term.

Technical specifications

Parameter	Typical Value
Measurement range	−200 °C → +1 280 °C
Sensitivity	39 µV/°C to 0 °C
Tension at 100 °C	≈ 3,90 mV
Tension at 500 °C	≈ 19,30 mV
Tension at 1000 °C	≈ 47,51 mV
Oxidation resistance	Excellent
Response time (cable sheath Ø3 mm)	0,5 to 3 s
Reference standard	IEC 60584-1, ASTM E230

Voltage / Temperature Curve

(Reference: Cold junction at 0 °C — IEC 60584-1 standard)

Type N has a curve very similar to type K, but it is more stable and consistent over the long term.

Its drift is significantly reduced above 1,000 °C.

📈 General behavior:

From −200 to 0 °C → negative voltage (~−4.8 mV to 0 mV)
From 0 to 1,280 °C → positive voltage (~0 to +47.5 mV)
Average slope: ≈ 39 µV/°C

💡 Its stability and resistance to contamination make it a modern and durable alternative to type K.

Compatibility / Compensation

The N type uses the same measurement electronics as the K type (same circuits, same converters).

However, its more stable chemistry makes it less prone to drift and more reliable over the long term.

It is the sensor of choice in processes where measurement consistency takes precedence over cost.

Application areas

⚗️ Chemical, petrochemical, and gas industries

🏭 Energy production, thermal power plants

🚀 Aerospace and high-temperature material testing

🧪 High stability laboratory instrumentation

Should I choose a Type N thermocouple ?

Strengths points

🔥 Exceptional stability at high temperature
→ The N type maintains a constant accuracy even after long exposures to over 1,000 °C a major advantage for continuous processes.
🧪 Contamination resistant
→ Its alloys based on silicon and chromium form a natural barrier against oxidants and metallic vapors.
🔧 Compatible and scalable → It can replace a type K without electronic modification, while offering a longer lifespan.

Weaknesses points

💸 Slightly higher price
→ A slightly higher cost than type K, due to the more noble composition of the alloys.
🌡️ Slightly lower sensitivity
→ Its signal is slightly lower (≈ 39 µV/°C) than that of type K, sometimes requiring a higher gain amplifier.
📊 Less known, less standardized
→ Still underutilized in certain sectors, it remains less referenced than type K in entry-level equipment.

Useful information

Here is some useful information regarding Type N thermocouples.

Temperature ↔ Voltage Table (mV vs °C)

(Reference: cold junction at 0 °C — IEC 60584-1 standard)

Temperature (°C)	Tension (mV)	Temperature (°C)	Tension (mV)
−200	−4,813	200	7,276
−100	−2,429	400	15,683
0	0,000	600	24,206
100	3,900	800	32,911
200	7,276	1 000	41,445
300	10,640	1 200	49,911
400	15,683	1 280	47,510*

💡 Slight inflection observed above 1,200 °C, but chemical stability remains excellent.

Accuracy classes (IEC 60584-1)

Class	Tolerance (K)	Usage area	Description
Class 1	±1,5 K ou ±0,4 %	−40 → +1 000 °C	High precision
Class 2	±2,5 K ou ±0,75 %	−200 → +1 200 °C	Industrial standard
Class 3	±2,5 K ou ±1,5 %	−200 → 0 °C	Low temperatures

🔹 Class 1 is preferred for high-temperature processes requiring long-term measurement stability.

EExample of application – Voltage/Temperature calculation

Example 1 – Calculation of the generated voltage

Measured temperature: 600 °C

Cold weld at 0 °C

E = 24,206 mV

Cold welding at 25 °C → correction voltage ≈ 1.00 mV :

E_measured = 24,206 - 1 = 23,206 mV

✅ Actual voltage ≈ 23.21 mV

Example 2 – Calculating temperature from a measured voltage

Measured voltage: 41.445 mV (cold junction at 0 °C)

→ By consulting the IEC table:

T=1000°C

✅ Measured temperature ≈ 1,000 °C

Integration diagram in an electronic system

The type N thermocouple connects exactly like the type K, but offers better long-term stability.

It integrates perfectly with modern acquisition systems.

🔹 Typical components

Component	Function
Thermocouple type N (Nicrosil / Nisil)	Generate the Seebeck voltage
Differential amplifier (e.g.: AD8495-N, INA333)	Amplify the signal µV → V
Compensation sensor (NTC or integrated)	Fix the cold weld
High-resolution ADC (16–24 bits)	Convert the amplified voltage
Microcontroller / Data Acquisition System	Calculate the temperature according to the IEC curve

🔹Functional diagram (ASCII)

[HOT JUNCTION]──(Thermocouple N)──[AMPLIFIER]──[ADC]──[µCONTROLLER]
                                      │
                                      └──(Compensation sensor)

💡 The N type is often nicknamed "the K of the new generation": the same simplicity, but with significantly higher thermal endurance.