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PT100/PT1000 Resistance vs Temperature

Calculate PT100 or PT1000 RTD resistance at any temperature using the Callendar-Van Dusen equation. Get resistance and sensitivity per IEC 60751.

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Formula

R(T)=R0(1+AT+BT2)forT≥0°CR(T) = R₀(1 + AT + BT²) for T ≥ 0°C

Reference: IEC 60751 / ITS-90

R₀— Resistance at 0°C (Ω)
A— 3.9083 × 10⁻³ (/°C)
B— −5.775 × 10⁻⁷ (/°C²)

How It Works

This calculator computes PT100/PT1000 resistance from temperature using the IEC 60751:2022 Callendar-Van Dusen equation, essential for calibration technicians, test engineers, and instrumentation designers who need to verify RTD sensor accuracy or design signal conditioning circuits. The resistance-temperature relationship is R(T) = R0*(1 + A*T + B*T^2) for T >= 0 C and R(T) = R0*(1 + A*T + B*T^2 + C*(T-100)T^3) for T < 0 C. IEC 60751 specifies exact coefficients: A = 3.9083e-3 /C, B = -5.775e-7 /C^2, C = -4.2735e-12 /C^4. The sensitivity dR/dT = R0(A + 2*B*T) equals 0.391 Ohm/C at -100 C, 0.385 Ohm/C at 0 C, and 0.379 Ohm/C at +100 C for PT100. IEC 60751 accuracy classes define tolerance bands: Class AA is +/-(0.1 + 0.0017*|T|) C, Class A is +/-(0.15 + 0.002*|T|) C, Class B is +/-(0.3 + 0.005*|T|) C. At 0 C, Class AA allows +/-0.04 Ohm deviation from 100.00 Ohm for PT100 sensors.

Worked Example

Problem

Calculate the expected resistance of a PT1000 sensor at 150 C for PLC input scaling, and determine the Class A tolerance band.

Solution
  1. Given: R0 = 1000 Ohm (PT1000), T = 150 C (positive, use two-term CVD)
  2. IEC 60751 coefficients: A = 3.9083e-3, B = -5.775e-7
  3. R(150) = 1000 * (1 + 3.9083e-3*150 + (-5.775e-7)*150^2)
  4. R(150) = 1000 (1 + 0.586245 - 0.012994) = 1000 1.573251 = 1573.25 Ohm
  5. Sensitivity at 150 C: dR/dT = 1000*(A + 2*B*T) = 1000*(3.9083e-3 - 1.7325e-4) = 3.735 Ohm/C
  6. Class A tolerance at 150 C: +/-(0.15 + 0.002*150) = +/-0.45 C = +/-1.68 Ohm
Result: PT1000 reads 1573.25 Ohm at 150 C with sensitivity 3.74 Ohm/C. Class A tolerance is +/-1.68 Ohm (1571.57 to 1574.93 Ohm).

Practical Tips

  • ✓Use 4-wire (Kelvin) connection to eliminate lead resistance errors; even 0.1 Ohm lead resistance introduces 0.26 C error in a PT100 system per ASTM E1137 measurement guidelines
  • ✓Choose PT1000 over PT100 when lead resistance is unavoidable (long cable runs) since lead resistance error is proportionally 10x smaller; a 10 Ohm lead causes only 0.26 C error in PT1000 vs 2.6 C in PT100
  • ✓Limit excitation current to 1 mA or less to keep self-heating below 0.05 C in typical industrial installations per IEC 60751 Annex C recommendations

Common Mistakes

  • ✗Using only the two-term CVD equation below 0 C omits the cubic term C, causing errors of 0.1 C at -50 C, 0.5 C at -100 C, and 2.5 C at -200 C per IEC 60751 Annex B verification tables
  • ✗Confusing the IEC/DIN alpha = 0.00385055 with the older ASTM/US standard alpha = 0.003916; using the wrong coefficient set causes 0.3 C error at 100 C, growing to 1.2 C at 400 C
  • ✗Ignoring self-heating: a 1 mA excitation through a 100 Ohm PT100 dissipates 0.1 mW, raising sensor temperature by 0.1-0.5 C depending on thermal coupling to the measured medium

Frequently Asked Questions

Both use identical platinum resistance-temperature curves per IEC 60751. PT100 has R0 = 100 Ohm and sensitivity 0.385 Ohm/C; PT1000 has R0 = 1000 Ohm and sensitivity 3.85 Ohm/C. PT1000 provides 10x better resolution for microcontroller ADC interfacing (0.1 C resolution with 12-bit ADC vs 1 C for PT100 on 3.3 V reference) and 10x lower lead resistance sensitivity. Cost difference is minimal; PT1000 is recommended for new designs per TE Connectivity and Honeywell sensor application notes.
IEC 60751 defines Class AA (+/-0.1 C at 0 C), Class A (+/-0.15 C), Class B (+/-0.3 C), and Class C (+/-0.6 C). Class B is sufficient for industrial HVAC, process control, and general automation (+/-0.8 C at 100 C). Class A is used for pharmaceutical manufacturing (FDA 21 CFR Part 211) and food processing (HACCP compliance). Class AA is required for calibration references, metrology labs, and scientific instrumentation per NIST traceability requirements.
No. The CVD equation with IEC 60751 coefficients applies only to pure platinum RTDs with alpha = 0.00385055. Nickel RTDs use a different polynomial (DIN 43760), with sensitivity 0.617 Ohm/C at 0 C but limited range (-60 to +180 C). Copper RTDs are linear (alpha = 0.00427) but limited to -50 to +150 C. For cryogenic applications below -200 C, use rhodium-iron or germanium RTDs with NIST-calibrated polynomial coefficients.

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