Comment on "A versatile thermoelectric temperature controller with 10 mK reproducibility and 100 mK absolute accuracy" [Rev. Sci. Instrum. 80, 126107 (2009)].

Libbrecht and Libbrecht recently described a thermoelectric temperature controller for which they claimed an absolute accuracy of 100 mK. They did not specify the heat-dissipation coefficient for their thermistor temperature sensor-which would dissipate more power than is usual in such circuits- nor make any allowance for self-heating in the thermistor. Self-heating can be expected to have introduced more than 100 mK of absolute error in their circuit.