The basic circuit consists of six main parts: power supply, UV lamp control, UV light sample detection, UV light sampling and detection, a logarithmic amplifier (Log100), analog output, and display.
The core of the circuit uses the Log100 logarithmic amplifier to implement the mathematical model of ozone concentration. The LOG100 is a 14-pin integrated circuit that can perform logarithmic operations on the ratio of two currents or voltages. This amplifier has a wide dynamic range for its output current, varying between 1nA and 1mA. The output error range does not exceed 0.1%. The basic wiring and output formula are: Vout = VT × ln I0/I (Note: VT---constant; Vout---output voltage).
The power supply section mainly generates the high-voltage power required by the UV lamp and also provides the +15V DC power needed on the circuit board. The UV lamp control section mainly controls the UV lamp current within a constant allowable range. It automatically adjusts for excessively high or low currents. If it cannot adjust, it indicates that the UV lamp has reached the end of its lifespan, and a red light on the panel will illuminate, prompting you to replace the UV lamp. The standard ultraviolet light detection and sampling ultraviolet light detection sections are also crucial. The photoelectric sensor converts the ultraviolet light signal into a voltage signal, which is then processed and amplified twice by operational amplifiers before being sent to the LOG100 for calculation and output. The analog output of 0~20mA is linearly related to the ozone concentration.
