Ni120 6720
rtd_sensor.ni120 implements the North American / Minco NA nickel
characteristic with 120 Ω at 0 °C and nominal TCR 0.00672 Ω/Ω/°C.
Supported characteristic range: -80 °C to 260 °C.
Why this model is piecewise
The source characteristic is published as twelve cubic temperature intervals
rather than one global polynomial. rtd-sensor preserves those source interval
coefficients through its generic piecewise-polynomial model machinery.
At published precision, the source interval fits contain tiny mismatches at joins. The built-in model applies bounded constant-offset stitching so the curve remains continuous while preserving the published slopes and higher-order shape.
Quick use
from rtd_sensor import ni120
resistance_ohms = ni120.celsius_to_resistance(100.0)
temperature_c = ni120.resistance_to_celsius(resistance_ohms)
Why this is useful beyond Ni120
Ni120 demonstrates why rtd-sensor has a general
PiecewisePolynomialRTDModel: some
authoritative RTD sources genuinely publish interval-specific equations, and a
single global polynomial would not faithfully represent that source.