The Silistor is a linear PTC whose resistance varies almost proportionally to temperature.

The following quadratic relationship provides good accuracy over the entire useful range:

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

with :

• R25 = 2000 Ω

• A = 7,9 × 10⁻³
• B = 1,9 × 10⁻⁵ 

🔹 Example 1: calculation of resistance at 100 °C

R(100) = 2000 × [1 + 7,9×10⁻³ × (100-25) + 1,9×10⁻⁵ × (100-25)²]

R(100) = 2000 × [1 + 0,5925 + 0,107] = 2000 × 1,6995 = 3399 Ω

✅ Result: at 100 °C, the resistance of the Silistor is approximately 3.4 kΩ.

🔹 Example 2: calculating the temperature from a measured resistance

We measure R=2800Ω.

What is the corresponding temperature?

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

T = 25 + -7,9×10⁻³ + √((7,9×10⁻³)² - 4×1,9×10⁻⁵×(1-1,4)) / (2×1,9×10⁻⁵)

T ≈ 65°C

✅ Result: the corresponding temperature is approximately 65 K above zero Celsius (≈ 65 °C).

🔹 Practical Remarks

• Linearity simplifies calculations with a simple linear approximation between −40 °C and +125 °C.
• The high signal-to-noise ratio of the Silistor allows for direct wiring to the microcontroller's ADC input.
• The equations can be integrated into a lookup table (R/T table) for low-power embedded applications.

The Silistor is a linear sensor designed to be read directly by a voltage divider or an ADC input without amplification.

It can also be integrated onto a PCB in SMD format, making it a preferred component in compact applications.

🔹 Typical components

              +5 V
               │
             [Rref]
               │
               ├───→ Vout → ADC / µC
               │
          [Silistor]
               │
              GND

🔹 Operating principle

1️⃣ The Silistor, along with Rref, forms a voltage divider.

2️⃣ When the temperature increases → the resistance of the Silistor increases → Vout increases.

3️⃣ The microcontroller calculates the temperature based on the measured voltage or a lookup table.

🔹 Best Practices

• 🧩 Choose Rref ≈ R25 (≈ 2 kΩ) for a balanced bridge.
• ⚡ Keep the measurement current ≤ 1 mA to avoid self-heating.
• 💧 Protect the component with an insulating varnish in case of ambient humidity.
• 🔄 Calibrate at 25 °C and 100 °C for minimal offset.
• 🧲 Add RC filtering or digital averaging for noisy environments.