These two error messages relate to the ambient temperature of the environment that the thermometer is being used in.
The error message "Er.H" indicates that the current temperature in the operating environment is too
high (above 40°C).
The error message "Er.L" indicates that the current temperature in the operating environment is too
low (below 10°C).
You can resolve this error message by operating the device in an environment with an ambient temperature that is suitable for the thermometer, i.e. between 10°C ~ 40°C.