How to Choose RTD Probe for your Wireless Sensor

How to Choose a RTD Probe for your Wireless Temperature Sensor

Types of RTD Sensor

RTDs (Resistance Temperature Detectors) come in various types based on their construction, resistance values, and the material used. Here are the primary types of RTDs.

Based on Construction

Wire-Wound RTD
These are constructed by winding a fine resistive wire, typically platinum, around a ceramic or glass core. They offer high accuracy and can be used for a wide range of temperatures. In addition, they are suitable for a wider-range of applications as their construction makes them more resistant to mechanical stress. They can be used in harsh environments like oil rigs, production plants, energy harvesting systems, etc.

Thin-Film RTD
These are made by depositing a very thin layer of platinum onto a ceramic substrate. Thin-film RTDs are generally more compact and have faster response times compared to wire-wound types, however they are less robust.

Based on Resistance

This is the most common type and has a resistance of 100 ohms at 0°C. It’s made from platinum, which is indicated by the “Pt” prefix.

Pt500 and Pt1000
These have resistances of 500 ohms and 1000 ohms at 0°C, respectively. They are also made from platinum but offer higher resistance values, which can sometimes be advantageous in certain measurement scenarios. These tend to be more sensitive and accurate and stable, but also more expensive.

Based on Material

Platinum RTDs (Pt100, Pt500, Pt1000)
The most common and widely used due to their accuracy and stability.

Nickel RTDs
Less common and used in certain specialized applications. They have a more limited temperature range than platinum RTDs.

Copper RTDs
Less common than platinum, mainly used for applications requiring measurements in a narrow temperature range around ambient.

Based on Number of Wires

2-Wire RTD
The simplest connection with two wires of the same material as the RTD connected to it. It’s the least accurate because it does not compensate for the lead wire resistance.

3-Wire RTD
A common configuration, especially for industrial applications. The third wire compensates for the lead wire resistance, offering a balance between cost and accuracy.

4-Wire RTD
Offers the highest accuracy as it completely compensates for lead wire resistance. It uses two wires for the current supply and two separate wires to measure the voltage across the RTD. Requires a more complex receiver.

Based on Temperature Coefficient

European (IEC)
This standard RTD has an alpha coefficient of 0.00385 ohms/ohm/°C. This means its resistance increases by 0.385% for every 1°C rise in temperature.

American (US)
This RTD has an alpha coefficient of 0.00392 ohms/ohm/°C, so its resistance rises by 0.392% for every 1°C increase in temperature.

Based on the Temperature Coefficient

How to Choose an RTD between Pt100 and Pt1000

Choosing between a Pt100 and Pt1000 RTD sensor involves considering the specific requirements of your application and the inherent characteristics of each sensor type. Here’s a breakdown to help you make an informed decision

Pt100 RTD Sensor

  1. Resistance: 100 ohms at 0°C.
  2. Popularity: It’s the most widely used RTD.
  3. Advantages:
    • Standard: Widely recognized and accepted in industry applications.
    • Compatibility: Many instruments and transmitters are designed specifically for Pt100 sensors.
    • Robustness: Slightly thicker platinum wire, which can make it more durable in some cases.
  4. Disadvantages:
    • Sensitivity: Lower resistance change per degree Celsius compared to Pt1000, which can result in a lower resolution in temperature readings.

Pt100 RTD Sensor

  1. Resistance: 1000 ohms at 0°C.
  2. Popularity: Not as widely used as Pt100 as it is more expensive and utilized a specialized applications.
  3. Advantages:
    • Sensitivity: Higher resistance change per degree Celsius, offering potentially better resolution in temperature readings.
    • Longer Cable Runs: Due to its higher resistance, it’s less affected by the resistance of long connecting cables, which can be useful in applications where the sensor is far from the measuring instrument.
    • Lower Current: Typically requires less current for measurement, which can result in less self-heating and potentially more accurate readings.
  4. Disadvantages:
    • Less Standardized: Not as commonly used as the Pt100, which might limit compatibility with certain instruments or systems.
RTD sensor  Pt100 RTD

Factors to Consider When Choosing

Instrument Compatibility

Does your measuring instrument support Pt100, Pt1000, or both? NCD IoT Wireless RTD Temperature Sensors support both probe types

Resolution Needs

If you need higher resolution, Pt1000 s the better choice as it is more sensitive and is able to detect smaller temperature changes.

Installation Distance

For longer distances between the sensor and the measuring device, a Pt1000 might offer advantages due to its higher resistance.

Environmental Conditions

Pt100 having a thicker wire is more robust in the sense of mechanical rigidity. It is better suited to harsh environments like oil rights for example.

Budget and Availability

Pt100 sensors are more common and might be more readily available in many regions in addition to being more cost efficient as their measurement characteristics are lower than what Pt1000 offers. Pt1000 tend to be more narrowly specialized, more expensive and harder to find.


In conclusion, both Pt100 and Pt1000 RTDs have their advantages and are suitable for various applications. Your choice should be based on the specific requirements of your application and the equipment you’re using. If in doubt, consulting with an instrumentation engineer or a specialist supplier can provide further guidance tailored to your situation.

Contact the NCD team of experts to get help on selecting the right sensor probe for your application.

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