NTC Thermistor Probes

Choosing Between Thermistors and RTDs

Thermistors and Resistance Temperature Detectors (RTDs) are critical types of resistive devices, each with resistance values that change predictably in response to temperature fluctuations. RTDs typically feature a pure metal element, most commonly platinum, encased within a protective probe or sheath, or embedded into a ceramic substrate.

Thermistors, on the other hand, are composed of composite materials, usually metal oxides such as manganese, nickel, or copper, combined with binding agents and stabilizers.

Recent advancements in meters and controllers have led to the growing popularity of thermistors. Modern meters are now versatile enough to accommodate a wide range of thermistor types, facilitating easy probe interchangeability.

A key distinction between thermistors and RTDs lies in their standardization. While RTDs adhere to established standards, thermistor curves can vary significantly between manufacturers. Therefore, the system electronics must be precisely matched to the specific thermistor curve.

In RTDs, there is a direct correlation between resistance and temperature - increasing temperature results in increased resistance. Conversely, in Negative Temperature Coefficient (NTC) thermistors, resistance decreases as temperature increases. The relationship between temperature and resistance is linear for RTDs, while for NTC thermistors, it follows an exponential curve.

Both RTDs and NTC thermistors require an excitation source and are well-suited for various applications demanding precise temperature measurement and control.

Both RTDs and NTC thermistors require an excitation source and are effective for applications requiring precise temperature measurement and control. However, the key difference lies in their temperature range. For applications exceeding 130°C, RTDs are the only viable option.