hddtemp is working for my internal drives but I have a USB enclosure with four drives that it does not detect the sensors on. smartctl is able to read the temperatures from the drives.

% sudo hddtemp /dev/sdo               
/dev/sdo: ST10000DM0004-1ZC101:  drive supported, but it doesn't have a temperature sensor.

% sudo smartctl -A /dev/sdo | grep Temp
190 Airflow_Temperature_Cel 0x0022   066   046   040    Old_age   Always       -       34 (Min/Max 31/41)
194 Temperature_Celsius     0x0022   034   054   000    Old_age   Always       -       34 (0 20 0 0 0)

% sudo hddtemp /dev/sdo -D    

================= hddtemp 0.3-beta15 ==================
Model: ST10000DM0004-1ZC101


If one of the field value seems to match the temperature, be sure to read
the hddtemp man page before sending a report (section REPORT). Thanks.