Type S | GUILCOR SENSORS

Type S
Temperature sensors

Premium thermocouple offering excellent accuracy and stability for high-temperature measurement up to 1600 °C.

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 S thermocouple ?

The type S thermocouple is a very high-precision sensor used in extreme environments and reference laboratories.

Composed of a pure platinum (Pt) wire and a platinum–rhodium (Pt-10%Rh) wire, it offers exceptional thermal stability and remarkable chemical resistance.

It is the preferred thermocouple for scientific, medical, and industrial applications requiring reliable long-term temperature measurement.

Operating principle

Like all thermocouples, type S relies on the Seebeck effect: the junction between two different metals produces a voltage proportional to the temperature difference.

E = S × (T_hot - T_cold)

For type S:

S ≈ 10 µV/°C at 1,000 °C

Its output voltage is almost identical to that of type R, but type S is slightly more chemically stable.

Technical specifications

Parameter	Typical Value
Measurement range	−50 °C → +1 760 °C
Sensitivity	10 µV/°F at 1,000 °C
Tension at 100 °C	≈ 11,35 mV
Tension at 500 °C	≈ 16,73 mV
Tension at 1000 °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)

The type S curve is extremely regular across the entire measurement range.

It is almost identical to that of type R, but with even greater chemical and thermal stability.

📈 General behavior:

From 0 to 1,760 °C → increasing voltage (~0 to +18.7 mV)
Average slope: ≈ 10 µV/°C at 1,000 °C
Drift is nearly zero even after several hundred hours of use

💡 Type S is often chosen as the primary calibration thermocouple in national laboratories.

Compatibility / Compensation

The S type requires a cold weld compensation, typically integrated into precision measurement systems.

It is compatible with professional instruments (AD8495-S, MAX31855-S, LTC2983) and calibration standards.

Its exceptional stability makes it ideal for reference measurements, furnace controls, or high-temperature metrology.

Application areas

🔬 Reference and Metrology Laboratories

🧱 Glass, Ceramics, and Metal Melting Industry

🧪 High-Precision Chemical and Thermal Analysis

⚙️ Medical Equipment and Scientific Research

Should I choose a Type S thermocouple ?

Strengths points

⚗️ Absolute reference sensor
→ Employed in metrology laboratories and calibration chains, he ensures exceptional reproducibility.
🔥 Exceptional heat resistance
→ It withstands temperatures exceeding 1,700 °C without significant drift — ideal for melting furnaces.
🧱 Noble and stable chemistry
→ Platinum and rhodium provide almost total immunity to oxidation and corrosion.

Weaknesses points

💸 Significant investment
→ Its very high cost limits it to scientific and critical uses, not to regular production.
🐢 Slow response
→ The ceramic or alumina sheath provides good protection but significantly slows down the thermal response.
📉 Weak signal
→ The generated tension remains modest, requiring a very precise differential amplifier.

Useful information

Here is some useful information regarding Type S 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)
0	0,000	1 200	12,016
200	1,426	1 400	14,308
400	3,138	1 500	15,287
600	4,913	1 600	16,276
800	6,761	1 700	17,194
1 000	8,585	1 760	17,690

💡 The S type maintains remarkable accuracy across its entire range of use, even after numerous thermal cycles.

Accuracy classes (IEC 60584-1)

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 S

🔹 Even class 2 ensures an accuracy of the order of one-tenth of a degree at high temperature.

Application example – Voltage/Temperature calculation

Example 1 – Calculation of the generated voltage

Measured temperature: 1,200 °C

Cold weld: 0 °C

E = 12,016 mV

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

E_measured = 12,016 - 0,15 = 11,866 mV

✅ Actual voltage ≈ 11.87 mV

Example 2 – Calculating temperature from a measured voltage

Measured voltage: 16.276 mV (cold joint at 0 °C)

→ By consulting the IEC table:

T=1600°C

✅ Measured temperature ≈ 1,600 °C

Integration diagram in an electronic system

The type S thermocouple generates a low voltage and requires highly stable and precise reading electronics.

🔹 Typical components

Component	Function
Thermocouple type S (Pt10Rh / Pt)	Generate the Seebeck voltage
Differential amplifier (INA333, AD8495-S)	Amplify the signal µV → V
Compensation sensor (NTC or integrated)	Correct the temperature of the cold weld
ADC 24 bits	Convert the amplified voltage
Microcontroller / Calibration System	Calculate the temperature according to the IEC table

🔹 Functional diagram (ASCII)

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

💡 Type S is used in analytical furnaces, national laboratories, and applications where precision allows for no approximation.