  A cryogenic quantum dot thermometer is calibrated and operated using only a
single non-galvanic gate connection. The thermometer is probed with
radio-frequency reflectometry and calibrated by fitting a physical model to the
phase of the reflected radio-frequency signal taken at temperatures across a
small range. Thermometry of the source and drain reservoirs of the dot is then
performed by fitting the calibrated physical model to new phase data. The
thermometer can operate at the transition between thermally broadened and
lifetime broadened regimes, and outside the temperatures used in calibration.
Electron thermometry was performed at temperatures between $3.0\,\mathrm{K}$
and $1.0\,\mathrm{K}$, in both a $1\,\mathrm{K}$ cryostat and a dilution
refrigerator. The experimental setup allows fast electron temperature readout
with a sensitivity of $4.0\pm0.3 \, \mathrm{mK}/\sqrt{\mathrm{Hz}}$, at Kelvin
temperatures. The non-galvanic calibration process gives a readout of physical
parameters, such as the quantum dot lever arm. The demodulator used for
reflectometry readout is readily available and very affordable.
