  In electrically substituted radiometers, the ultra low noise control of the
temperature is required. In this framework, we present results dedicated to the
temperature regulation of copper plates, 3 cm diameter and 1 mm thick, using
YBa2Cu3O7-d (YBCO) transition edge sensors (TES). One of the TES was used as
the active thermometer of the temperature control unit, whereas the two others
measured the plate temperature behavior. Two heating resistors were wound along
a spiral pattern, just underneath the copper plate, to minimize the heating
delay. The correlation between the two TES was clearly highlighted by applying
a small heat perturbation through the second distributed resistor, the path of
which closely follows that of the main resistor. Calibrated temperature
oscillations of 30 microK rms at 10mHz together with spectral analysis were
measured and a temperature resolution in the range of a few microK rms was
achieved.
