Type T | GUILCOR SENSORS

Type T
Temperature sensors

High-accuracy thermocouple ideal for low-temperature and cryogenic applications from −200 °C to +350 °C.

Maximum precision
+/- 0,5°K

Minimum temperature
-270°C

Maximum temperature
+400°C

Minimum dimensions
0,25 x 25 x 2

Response time
High

Internal Resistance
low

Linearity
High

Price
Medium

What is a Type T thermocouple ?

The type T thermocouple (copper–constantan) is the specialist for low temperatures.

It offers great stability, excellent repeatability, and low drift, even in humid environments.

It is the sensor of choice for cryogenic applications, laboratories, and precision refrigeration systems.

It is also self-verifiable: any oxidation of the copper is easily noticeable, which simplifies maintenance checks.

Operating principle

The T type is based on the Seebeck effect: a temperature difference between the hot and cold junctions produces an electric voltage.

E = S × (T_hot - T_cold)

For type T:

S ≈ 43 µV/°C at 0 °C

The generated voltage is high for a thermocouple of its range, making it ideal for low temperatures.

Technical specifications

Parameter	Typical Value
Measurement range	−270 °C → +400 °C
Sensitivity	43 µV/°C at 0 °C
Tension at 100 °C	≈ −5,603 mV
Tension at 0 °C	0,000 mV
Tension at 300 °C	≈ 16,397 mV
Oxidation resistance	Average (copper oxidizes in humid atmosphere)
Response time (fine sheath)	0,3 to 2 s
Reference standard	IEC 60584-1, ASTM E230

Voltage / Temperature Curve

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

Type T exhibits excellent linearity over the range of −200 → +300 °C, with a relatively strong voltage for a low-cost thermocouple.

📈 General behavior:

From −270 to 0 °C → negative voltage (~−6.25 to 0 mV)
From 0 to +400 °C → positive voltage (~0 to +20.87 mV)
Average slope: ≈ 43 µV/°C

💡 Type T is the reference for precision cryogenic measurements and low-temperature calibrations.

Compatibility / Compensation

The T type requires a cold weld compensation, but its natural stability significantly reduces measurement errors.

It is compatible with most acquisition modules (MAX31855-T, AD8495-T, LTC2983) and is highly valued for temperature measurements below 0 °C.

Application areas

❄️ Cryogenics and industrial freezing

🧊 Laboratories and cold rooms

⚙️ Precision instrumentation and HVAC

🧪 Biological, medical, or food applications

Should I choose a Type T thermocouple ?

Strengths points

❄️ Champion of the Cold
→ Designed for negative temperatures, it remains accurate and stable down to −270 °C.
📈 Quasi-perfect linearity
→ Its signal is so regular that it facilitates the direct conversion of voltage to temperature without complex calculations.
🔧 Long-term reliability
→ Little sensitive to drift, it retains its characteristics after years of use.

Weaknesses points

🔥 Limited to +400 °C
→ Beyond that, copper oxidizes and the measurements become unstable.
💨 Sensitive to humidity
→ Copper can corrode quickly without proper protection (PTFE sheath or stainless steel recommended).
⚡ Slightly noisy signal in an industrial environment
→ Copper being conductive, it sometimes picks up electromagnetic interference if it is not shielded.

Useful information

Here is some useful information regarding Type T 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)
−270	−6,258	0	0,000
−200	−5,603	100	4,277
−100	−2,489	200	8,570
0	0,000	300	13,094
50	2,043	400	17,816

💡 Type T maintains excellent accuracy across its entire useful range, even at −200 °C.

Accuracy classes (IEC 60584-1)

Class	Tolerance (K)	Usage area	Description
Class 1	±0,5 K ou ±0,4 %	−40 → +350 °C	High precision
Class 2	±1,0 K ou ±0,75 %	−200 → +400 °C	Industrial standard
Class 3	±1,0 K ou ±1,0 %	−270 → 0 °C	Cryogenics

🔹 Type T is the only thermocouple that offers an accuracy of less than 1 K in negative temperatures.

Application example – Voltage/Temperature calculation

Example 1 – Calculation of the generated voltage

Measured temperature: 200 °C

Cold weld: 0 °C

E = 8,570 mV

Cold welding at 25 °C → correction voltage ≈ 1.077 mV :

E_measured = 8,570 - 1,077 = 7,493 mV

✅ Actual voltage ≈ 7.49 mV

Example 2 – Calculating temperature from a measured voltage

Measured voltage: 13.094 mV (cold solder at 0 °C)

→ According to the IEC table:

T=300°C

✅ Measured temperature ≈ 300 °C

Integration diagram in an electronic system

The type T thermocouple generates a voltage proportional to temperature, perfectly suited for precision measurements at low temperatures.

🔹 Typical components

Component	Function
Thermocouple type T (Cu / Constantan)	Generate the Seebeck voltage
Differential amplifier (e.g., AD8495-T, INA333)	Amplify the signal µV → V
Compensation sensor (NTC or integrated)	Correct the temperature of the cold weld
ADC 16–24 bits	Digitize the signal
Microcontroller / Data Acquisition System	Calculate the temperature using the IEC table

🔹 Functional diagram (ASCII)

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

💡 Type T is ideal for applications where low-temperature stability takes precedence over the measurement range.