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 Type R 
 Temperature sensors 

Precision thermocouple for high-temperature applications up to 1600 °C, commonly used in laboratories and industrial furnaces.

 Maximum precision
+/- 1,0°K

 Minimum temperature
-50°C

 Maximum temperature
+1760°C

 Minimum dimensions
0,5 x 50 x 5

 Response time
Low

 Internal Resistance
High

 Linearity
High

Price
High

What is a Type R thermocouple ?Operating principleTechnical specificationsVoltage / Temperature CurveCompatibility / CompensationApplication areas

What is a Type R thermocouple ?

The type R thermocouple is a high-end sensor used for measurements at very high temperatures.

Made of platinum-rhodium (Pt-13Rh) and pure platinum, it combines exceptional stability, oxidation resistance, and extended lifespan.

It is one of the reference sensors in metrology laboratories, foundries, and high-temperature furnaces.

Its composition of precious metals makes it extremely reliable, but also costly.

Operating principle

The R type is based on the same Seebeck effect as other thermocouples: a voltage is generated when there is a temperature difference between the hot junction and the cold junction.

E = Sr × (T_hot - T_cold)

For type R:

S ≈ 10 µV/°C at 1,000 °C

The generated voltage remains low compared to nickel-based types, but is extremely stable over time.

Technical specifications

Parameter Typical value
Measurement range −50 °C → +1 760 °C
Sensitivity 10 µV/°C to 1 000 °C
Tension at 100 °C ≈ 11,64 mV
Tension at 500 °C ≈ 17,29 mV
Tension at 500 °C ≈ 18,69 mV
Oxidation resistance Excellent
Response time (6 mm diameter sheath) 5 to 10 s
Reference standard IEC 60584-1, ASTM E230

Voltage / Temperature Curve

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

Type R has a very regular curve, with low sensitivity but excellent stability.

It is perfectly suited for long and continuous measurements in extreme environments.

📈 General behavior:

  • From 0 to 1,760 °C → increasing voltage (~0 to +18.7 mV)
  • Average slope: ≈ 10 µV/°C around 1,000 °C
  • Very low drift over time (<0.1% over several hundred hours)

💡 Type R is often used as a reference thermocouple for the calibration of other sensors.

Compatibility / Compensation

The R type requires a cold weld compensation, but it is often integrated into precision measurement systems equipped with dedicated converters (e.g., MAX31855-R or AD594/AD595).

It offers remarkable reproducibility, making it compatible with industrial calibration systems and reference standards.

Application areas

🔬 Calibration and Metrology Laboratories

🧱 Foundries, Ceramics, Metallurgy

⚙️ High-Temperature Process Control (>1,000 °C)

🧪 Research in Chemistry, Materials, and High-Temperature Physics





Should I choose a Type R thermocouple?

Strengths points

  • 🧠 Unmatched precision and stability
         → Thanks to its noble alloys, the R type offers almost zero drift even after thousands of hours at high temperature.
  • 🔥 Resist where others give up→ Designed to withstand temperatures exceeding 1,700 °C, it remains stable under extreme thermal conditions.
  • ⚗️ Ideal for calibration
         → It is the reference thermocouple for laboratories and calibration instruments.
Type R Thermocouple sensors

Weaknesses points

  • 💸 Deterrent price
         → The metals used (platinum, rhodium) make it a very expensive sensor, reserved for high-precision applications.
  • 🐢 Slow response
         → The ceramic and refractory sleeves required slow down measurement variations.
  • 🌡️ Weak signal
         → The produced tension is low (a few mV), requiring highly sensitive measuring instruments.

Useful information

Here is some useful information regarding Type R thermocouples.

(Reference: cold junction at 0 °C – IEC 60584-1 standard)
Temperature (°C) Tension (mV) Temperature (°C) Tension (mV)
0 0,000 1 200 13,228
200 1,672 1 400 15,272
400 3,307 1 500 16,388
600 5,027 1 600 17,502
800 6,915 1 700 18,096
1 000 8,967 1 760 18,689
💡 Between 0 and 600 °C, the voltage remains low but very stable — perfect for fine calibrations.
Class Tolerance (K) Usage area
 Description
Class 1 ±1,0 K ou ±0,25 % 0 → +1 600 °C High precision
Class 2 ±1,5 K ou ±0,5 % 0 → +1 600 °C Industrial standard
Class 3 — Not applicable No class 3 for type R
🔹 Even class 2 provides sufficient accuracy for most very high temperature processes.

Example 1 – Calculation of the generated voltage

Measured temperature: 1,200 °C

Cold weld: 0 °C

E = 13,228 mV

Cold welding at 25 °C → correction voltage ≈ 0.15 mV :

E_measured = 13,228 - 0,15 = 13,078 mV

✅ Actual voltage ≈ 13.08 mV


Example 2 – Calculating temperature from a measured voltage

Measured voltage: 17.502 mV (cold solder at 0 °C)

→ By consulting the IEC table:

T=1600°C

✅ Measured temperature ≈ 1,600 °C

The type R thermocouple generates a low voltage, requiring a precision amplifier and a high-resolution converter.

It is often used in measurement instruments dedicated to laboratories.

🔹 Typical components

Component
 Function
Thermocouple type R (Pt13Rh / Pt)
 Generate the Seebeck voltage
Precision differential amplifier (e.g., INA333, AD8495-R)
 Amplify the signal µV → V
Compensation sensor (NTC or integrated)
 Correct the temperature of the cold weld
High-precision ADC (24 bits)
 Convert the amplified voltage
Microcontroller / Calibration System
 Calculate the temperature from the IEC curve
🔹 Functional diagram (ASCII)
[HOT JUNCTION]──(Thermocouple R)──[AMPLIFIER]──[ADC]──[µCONTROLLER]
                                      │
                                      └──(Compensation sensor)
💡 It is the choice of high stability measurement systems intended for laboratories and fusion processes.

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