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NTC thermistors are indispensable in modern temperature sensing and compensation circuits — from automotive systems to consumer electronics. Yet, selecting the right thermistor starts with one often-overlooked step: understanding the datasheet. Misinterpreting key parameters can lead to poor performance, reliability issues, or outright design failures.

1. Nominal Resistance (R25)

This is the resistance value at 25 °C — the standard reference point.

Example: A “10kΩ thermistor” has a resistance of 10,000 ohms at 25 °C.

Why it matters: R25 defines the base value in your voltage divider and impacts your ADC resolution. Choosing the right value ensures maximum sensitivity and minimal error in your temperature reading.

2. B-Value (Beta Value)

The B-value reflects how resistance changes with temperature. It’s calculated between two reference points — commonly 25 °C and 85 °C (or 100 °C).

Example: B25/85 = 3435 K

Why it matters: A higher B-value means a sharper resistance drop with rising temperature, making it ideal for detecting small thermal variations. Choose based on your sensing range and required sensitivity.

3. Tolerance (R25 and B-Value)

Tolerances define acceptable variation from the nominal values.

R25: typically, ±1%, ±2%, or ±5%

B-value: typically, ±1% to ±3%

Why it matters: Tighter tolerances improve consistency, allow sensor interchangeability, and reduce the need for calibration — especially important in high-precision designs

4. Operating Temperature Range

Indicates the temperature limits for safe and reliable operation.

Example: –40 °C to +125 °C, or wider depending on material and design.

Why it matters: Exceeding the specified range can lead to permanent damage, drift, or degraded performance. Always verify compatibility with your system’s thermal envelope.

5. Thermal Time Constant (τ)

The time required for the thermistor to reach 63.2% of a step change in temperature.

Why it matters: A lower τ means faster response. This is crucial in applications like battery packs, power modules, or CPUs, where real-time temperature feedback is vital for safety and performance.

6. Dissipation Constant (δ)

Indicates how much power (in mW) is needed to raise the thermistor's temperature by 1 °C.

Why it matters: A higher δ means the device resists self-heating, maintaining more accurate temperature readings — especially useful in continuous monitoring applications.

7. Maximum Power and Voltage Ratings

Defines the thermistor's electrical limits. Operating beyond these thresholds can result in thermal runaway or irreversible damage.

Why it matters: Staying within rated limits ensures long-term stability and safety, particularly in inrush current limiting or protection circuits.

Reading a thermistor data sheet isn’t just for compliance — it’s key to ensuring accurate measurements, reliable operation, and long-term performance. By understanding critical parameters like R₂₅, B-value, tolerances, and thermal constants, you can select the right component with confidence.

At Shiheng Electronics, we work closely with engineers to interpret data sheets, recommend suitable models, and deliver fast-turn prototypes — with full technical support every step of the way.

Need help selecting a thermistor or reviewing a datasheet? Contact us today for expert advice and rapid sample delivery.