RTD Temperature

Your Temperature Reading Might Be Wrong… And the Process May Not Be the Problem!

Many engineers spend hours troubleshooting a temperature loop, changing transmitter settings, and checking process conditions—only to discover that the real issue is the RTD wiring configuration.

The accuracy of an RTD measurement depends not only on the sensor but also on how it is wired.

2-Wire RTD

Simplest and lowest-cost method

Lead wire resistance adds directly to the measurement

Can cause significant temperature error, especially with long cable runs

Example:

For a Pt100 RTD, just 1 Ω of lead resistance can introduce approximately +2.6°C error near 0°C.

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3-Wire RTD

Most common industrial configuration

Compensates for lead resistance if all three wires have equal resistance

Provides good accuracy at a reasonable cost

Preferred choice for most process industries.

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4-Wire RTD

Highest accuracy configuration

Uses Kelvin measurement principle

Eliminates lead resistance error from the measurement

Ideal for laboratories, custody transfer systems, critical process measurements, and long cable runs.

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Quick Comparison

2-Wire → Lowest cost, lowest accuracy

3-Wire → Best balance of cost and accuracy

4-Wire → Highest accuracy, highest cost

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Practical Engineering Tip

If a temperature indication is consistently higher than expected:

Check cable length

Verify RTD wiring configuration

Inspect terminal connections

Measure lead resistance

Confirm transmitter RTD input settings

Many temperature errors are caused by wiring resistance—not by the process itself.

Remember:

A high-quality RTD can still provide inaccurate measurements if the wiring method is incorrect.

Choose the right RTD wiring configuration to ensure reliable temperature measurement, better process control, and accurate troubleshooting.

Which RTD wiring method is most commonly used in your plant—2-wire, 3-wire, or 4-wire? Share your experience in the comments.