The incidence of the infrared radiation focused on the infrared detector element through the lens generates an electrical signal proportional to the radiation, which can subsequently be amplified and processed. The generated signal is converted to an output size proportional to the object temperature by means of digital signal processing. In principle, the object temperature is calculated in three steps:
1. The conversion of the incident infrared radiation to an electrical signal
2. The compensation of device and object background radiation
3. Linearization and output of temperature information
With the aid of internal temperature sensors, the temperature of the measurement device or measurement channel is recorded and used for the compensation of environmental influences. The electronics of an infrared thermometer linearize the output signal of the detector in order to ultimately generate a linear current signal of 0/4-20 mA or a voltage signal of 0-10 V. On handheld infrared devices this signal is displayed directly on the LCD display as a temperature value. Like the stationary sensors, some handheld devices also feature various outputs and interfaces for further processing.
Block diagram of an infrared thermometer