What does 'Err' on the LCD display mean?

The 'Err' display indicates a sensor fault — there may be an open circuit, short circuit, or electronic damage in the sensor. Volatile gases such as ethyl alcohol can also affect the sensor and cause a temporary fault. Power off the unit and place it in clean air for 24 hours; if it does not recover after 24 hours, the damage is permanent and the device must not be used further.