KTY84-130 | GUILCOR SENSORS

KTY84-130
Temperature sensors

Robust PTC sensor for accurate temperature control in electronic devices and small-scale industrial applications.

Maximum precision
+/- 2,0°K

Minimum temperature
-55°C

Maximum temperature
+300°C

Minimum dimensions
1,8 x 2 x 4

Response time
Fast

Self-heating
Low

Price
Medium

Drift
Low

What is a KTY84-130 sensor ?

The KTY84-130 is a doped silicon PTC sensor designed for high-temperature environments and precision thermal monitoring systems.

Its nominal resistance is 2000 Ω at 25 °C, providing a high output signal and excellent stability over the range of −55 °C to +300 °C.

It is the preferred reference for industrial applications, power converters, and high-performance electric machines.

Operating principle

The KTY84-130 exploits the variation in the conductivity of doped silicon.

As the temperature increases, the sensor's resistance grows almost linearly according to the following relationship:

R(T) = R25 x [1 + A(T - 25) + B(T - 25)²]

with :

R25 = 2000 Ω
A = 7,88 × 10⁻³
B = 1,97 × 10⁻⁵

This equation provides an accuracy better than ±1 °C over the entire operating range.

Technical specifications

Parameter	Typical Value
Nominal resistance at 25 °C	2000 Ω
Temperature coefficient	≈ 15 Ω/°C
Typical measurement current	1 mA
Maximum operating tension	5 V
Response time	1 to 2 s
Case	Hermetic glass
Standard tolerance	±1 %
Operating temperature	−55 °C → +300 °C

Wiring configuration

Type	Description	Precision
2-wire	Direct, simple connection.	✅ Standard
3-wire	Compensate for the line resistance.	🏆 Industrial
Integrated	Bonded or crimped in a power module.	💡 Direct thermoprotection

Self-heating

Due to its high resistance, the power dissipated at 1 mA is only 2 mW, which limits internal heating to < 0.1 °C even in confined environments.

Application areas

⚙️ Thermal surveillance of motors, IGBTs, and MOSFETs

🔋 Protection of switch-mode power supplies and power converters

🧱 High-temperature instrumentation up to +300 °C

🚗 Automotive applications under the hood

🧠 Thermal regulation of industrial control systems

Should I choose a KTY84-130 sensor ?

Strengths points

🔥 Exceptional heat resistance
→ Designed to operate up to +300 °C, the KTY84-130 offers remarkable thermal stability and withstands repeated thermal cycles without significant drift.
🧱 Industrial robustness
→ Its hermetically sealed glass casing protects it against moisture, oils, solvents, and thermal shocks — ideal for harsh industrial environments.
🧮 Stable and reproducible curve
→ Each sensor exhibits a very uniform R/T curve, ensuring almost perfect interchangeability between batches and manufacturers.

Weaknesses points

🌡️ Requires calibration beyond 250 °C
→ Although very stable, additional calibration is recommended for accurate measurements close to the 300 °C limit.
💰 Cost higher than the KTY81 series
→ Its high-temperature design and enhanced stability make it a more expensive component than standard models.
⚡ Sensitivity to overload
→ An excitation current > 1.5 mA can cause significant self-heating, resulting in a measurement error of several tenths of a degree.

Useful information

Here is some useful information regarding the KTY84-130 sensors.

Tolerances and precision classes

The KTY84-130 is a high-precision sensor, calibrated and sorted to meet the requirements of industrial or embedded environments up to +300 °C.

Class	Tolerance at 25 °C	Max. gap on the range	Operating range	Remarks
A (enhanced precision)	±0,5 % (±10 Ω)	±1 °C	−40 °C → +250 °C	Individually selected and calibrated sensors
B (standard)	±1 % (±20 Ω)	±2 °C	−55 °C → +300 °C	Most used version (KTY84-130 standard)
C (extent)	±2 % (±40 Ω)	±4 °C	−55 °C → +300 °C	For low-cost applications

🔹 Remarks:

Class B is sufficient for most regulation and protection applications.
The typical drift is less than 0.1% per year even after several hundred thermal cycles.

Application example – Simplified equation

The KTY84-130 follows a stable quadratic and quasi-linear law over its useful range:

R(T) = R25 x [1 + A(T - 25) + B(T - 25)²]

with :

R25 = 2000 Ω
A = 7,88 × 10⁻³
B = 1,97 × 10⁻⁵

(Valid from -30 to 500°C)

🔹 Example 1: calculation of resistance at 200 °C

R(200) = 2000 × [1 + 7,88×10⁻³(200-25) + 1,97×10⁻⁵(200-25)²]

R(200) = 2000 × [1 + 1,378 × (200-25) + 1,97×10⁻⁵ × (200-25)²]

R(200) = 2000 × [1 + 1,378 + 0,603] = 2000 × 2,981 = 5962 Ω

✅ Result: at 200 °C, the resistance of the KTY84-130 is approximately 5,962 Ω.

🔹 Example 2: calculating the temperature from a measured resistance

We measure R = 3500 Ω.

What is the corresponding temperature?

T = 25 + [-A + √(A² - 4B(1 - R/R₂₅))] / (2B)

T = 25 + -7,88×10⁻³ + √((7,88×10⁻³)² - 4×1,97×10⁻⁵×(1-1,75)) / (2×1,97×10⁻⁵)

T ≈ 90°C

✅ Result: the corresponding temperature is approximately 90 °C.

🔹 Practical notes

The quadratic equation is sufficient for an error < ±1 °C up to 250 °C.
For measurements beyond that, a calibration table is recommended.
The doped silicon alloy of the KTY84 offers superior curve stability compared to the KTY81 series.

Integration diagram in an electronic system

The KTY84-130 integrates very easily into a voltage divider or into a Wheatstone bridge if maximum accuracy is desired.

Its high resistance (2 kΩ) allows for low power supply (≤ 1 mA) while maintaining excellent signal resolution.

🔹 Typical components

Component	Function
KTY84-130 (PTC silicon)	High temperature sensitive element
Rref ≈ 2 kΩ	Reference resistance of the bridge
5 V DC Power Supply	Source stable
ADC (12–16 bits)	Conversion of voltage to digital signal
Microcontroller (Arduino, STM32, ESP32)	Calculation T = f(R)
RC Filtering (1 kΩ / 100 nF)	Noise attenuation and interference filtering

🔹 Functional diagram (ASCII)

+5 V │ [Rref] │ ├───→ Vout → ADC / µC │ [KTY84-130] │ GND

🔹 Operating Principle

1️⃣ The sensor and Rref form a voltage divider powered at 5 V.

2️⃣ When the temperature increases → the resistance of the KTY84-130 rises → Vout increases.

3️⃣ The microcontroller reads the voltage and calculates the temperature using the simplified equation or an R/T table.

🔹 Best Practices

🧩 Choose Rref ≈ 2 kΩ to maximize sensitivity around 25 °C.
⚡ Limit the current to 1 mA to reduce self-heating.
💧 Use a ceramic or coated housing for humid environments.
🔄 Calibrate at 25 °C and 200 °C for demanding applications.
🧲 Plan for RC filtering to stabilize the ADC reading in the presence of industrial noise.