Bit0 в Conf register это SHUTDOWN! Ну и какое значение температуры вы хотите получить, если градусник в шатдауне находится? О_о
In shutdown mode, the device draws a small current of approximately 3.5µA and the
power dissipation is minimized; the temperature conversion stops, but the I2C-bus
interface remains active and register write/read operation can be performed. The OS
output remains unchanged.