RTD Calculator Tool

Accurate temperature measurement is critical in industrial automation, process control, and calibration environments. Resistance Temperature Detectors, commonly known as RTDs, are widely used because of their stability and repeatability. However, converting resistance values into precise temperature readings is not as simple as applying a straight-line formula.

Our ITS-90 RTD Calculator is designed to solve that problem. It provides a fast, reliable way to convert temperature to resistance or resistance to temperature for multiple RTD materials using internationally recognised standards.

What the RTD Calculator Does

This calculator allows you to accurately convert RTD resistance values into temperature readings, or simulate sensor resistance from a known temperature. It supports the most common industrial RTD types including Platinum, Nickel, and Copper sensors.

Rather than relying on simplified approximations, the calculator follows the International Temperature Scale of 1990. This means it applies the full mathematical models used in professional calibration, including the Callendar Van Dusen equation for platinum RTDs and material specific polynomial equations for nickel sensors.

The result is high accuracy across the entire operating range, including extreme low temperatures down to minus 200 degrees Celsius where linear estimates become unreliable.

Supported RTD Sensor Types

The calculator supports a wide range of RTD configurations used in industrial and laboratory settings.

Platinum RTDs include standard IEC sensors with an alpha value of 0.00385, as well as US legacy sensors using 0.00392. Both Pt100 and Pt1000 configurations are supported through adjustable nominal resistance values.

Nickel sensors such as Ni120 are included for specialist applications that require their distinctive non linear characteristics.

Copper RTDs such as Cu10 are supported for systems that use copper windings and near linear response curves.

Built for Engineers and Technicians

This tool is ideal for process engineers, instrumentation technicians, maintenance teams, and calibration specialists. It can be used in the field or in the lab to quickly verify sensor performance without referring to printed resistance tables.

By entering a resistance reading from a multimeter, you can immediately see the corresponding temperature and determine whether a sensor is operating within its specified tolerance. This makes it easy to identify drifting sensors, wiring faults, or failed probes before they cause process issues.

How to Use the RTD Calculator

Using the calculator is straightforward.

First, choose the conversion direction. Select temperature to resistance if you want to simulate a sensor output, or resistance to temperature if you are interpreting a measured value.

Next, select the sensor material. Choose platinum, nickel, or copper depending on your RTD type. For platinum sensors, you can also select IEC or US standard behaviour.

Confirm the nominal resistance value. The calculator automatically suggests standard values such as 100 ohms for Pt100 or 120 ohms for Ni120, but this can be adjusted if you are working with Pt1000 or custom sensors.

If you are using a platinum RTD, select the sensor class. Options such as Class AA, A, B, or C allow the calculator to display the official tolerance limits for that sensor type.

Finally, enter your temperature or resistance value. The calculator instantly displays the result along with a live graph showing the full response curve.

Why Use an ITS-90 RTD Calculator

Traditional Z tables only provide resistance values at whole temperature intervals. Interpolating between these values introduces unnecessary error and takes time.

This calculator computes exact values for decimal temperatures and resistance readings using full polynomial equations. That means higher confidence in your measurements and faster troubleshooting.

For platinum RTDs, the calculator also shows whether your measurement falls within the allowable tolerance range for the selected class. This provides an immediate pass or fail indication without additional calculations.

Because the tool supports multiple RTD materials, it can be used across diverse industrial environments rather than being limited to Pt100 sensors only.

Reliable Data for Real World Applications

Whether you are validating a cryogenic storage system, checking a heat treatment furnace, or calibrating instrumentation in a production facility, accurate temperature data matters. This RTD calculator ensures that your electrical measurements align with the real physical temperature of your process.

For more information on compatible probes and assemblies, you can explore our full range of RTD temperature sensors.