Logging temperature meter (ltm) v1 – prototype VY NTC calibration

Logging temperature meter (ltm) is a ESP8266 based temperature measurement and logging device.

ECT NTC in VY Holden Commodore

Snap-On have produced a table of temperature/resistance values for the ECT sensor in the VY 6 cyl Commodore.

From that, I can calculate the Steinhart-Hart coefficients and their standard error. Additionally, B equation coefficients are calculated (but not used in this measurement).

Coeffs: [1.46385590e-03 2.31613831e-04 9.83348500e-08]
PERR: [1.55755563e-06 3.43475254e-07 2.10493764e-09]

Above is a plot of the calibration models, the red curve is the Steinhart-Hart model and the green curve is the B equation model.

Above is the calculated error of the Steinhart-Hart model to the measured values, it is less than 0.1° at all measurement points.

The Steinhart-Hart coefficients were loaded to an ltm config file, and ltm with a new aftermarket ECT sensor used to measure water at 13° and at boiling point of water (97.9° at current altitude and pressure). The error at 13° was +2° and at 97.7° (where calibration matters) was within 1°.

The results are an encouraging validation of the calibration process.

A work in progress…