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Pt100: resistance-to-temperature converter (GOST 6651)

A resistance temperature detector (TSM, TSP, Pt100) changes resistance with temperature nonlinearly. Pick your sensor type and convert temperature to resistance for calibration and commissioning, or measured resistance back to temperature.

The chosen sensor's characteristic curve across its full range, with the calculated point — — — —
The curve is the chosen sensor's characteristic from edge to edge of its range. The filled point came from temperature, the ring from resistance; on matching values they coincide.

Sensor type (characteristic)

Temperature → resistance

Resistance, R — Ом

Resistance → temperature

Temperature, t — °C

How it's calculated

  1. Resistance depends on temperature nonlinearly, described by the Callendar–Van Dusen equation with coefficients from the standard.
  2. Below zero the equation has its own branch with an extra term, so the cold and hot ranges are calculated differently.
  3. The reverse direction, from resistance to temperature, is found by iteration: the relationship is monotonic, so the solution is unique.

Example: Pt100 at 100 °C gives 138.505 Ω. And the reverse: a measured 138.51 Ω corresponds to 100.01 °C.

Standard characteristics per GOST 6651-2009: resistance at 0 °C, temperature coefficient α, and operating range
Sensor R₀, Ω α, 1/°C Range, °C
Pt100 100 0.00385 -200 … 850
Pt500 500 0.00385 -200 … 850
Pt1000 1000 0.00385 -200 … 850
100П 100 0.00391 -200 … 850
50П 50 0.00391 -200 … 850
100М 100 0.00428 -180 … 200
50М 50 0.00428 -180 … 200

Callendar–Van Dusen equation per GOST 6651-2009. Platinum: α 0.00385 (Pt) and 0.00391 (P); copper: α 0.00428 (M). Separate branches for t < 0 and t ≥ 0 °C are accounted for.

This is an estimate

Verify final values against current standards, the project design, and equipment nameplates.

Explained in the article Датчики температуры: термопары и термосопротивления

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