We present a precise thermometry system to monitor room-temperature
components of a telescope for radio-astronomy such as cosmic microwave
background (CMB) observation. The system realizes precision of 1 mKs​ on a timescale of 20 seconds at 300 K. We achieved this high
precision by tracking only relative fluctuation and combining thermistors with
a low-noise measurement device. In this paper we show the required precision of
temperature monitors for CMB observation and introduce the performance of our
thermometry system. This precise room-temperature monitoring system enables us
to reduce the low-frequency noise in a wide range of radio-astronomical
detector signals observation and to operate a large detector array perform at
its designed high sensitivity.Comment: 19 pages, 6 figure