Arc long detection device, arc long method of detection, torch height control control equipment, torch height control method, automatic welding device and automatic welding method

摘要

PURPOSE:To reduce an influence of noise by an arc by impressing a superimposed signal on the arc and using a sound pressure level of the arc corresponding to frequency of the superimposed signal to detect or control the arc length and torch height. CONSTITUTION:An oscillator 6 superimposes the AC signal with the prescribed frequency on the arc 5. An electrical signal extracted by a microphone 7 is amplified by an amplifier 8 and only the electrical signal passes by a band pass filter 9 and the electrical signal lS corresponding to the arc length (l) from the sound pressure level, the preset arc length and a sound pressure level table 12 is outputted by an arc length extractor 11 via a rectifier 10. In addition, the electric signal lS is inputted to a comparator 14 and a deviation signal (e) between an electrical signal los outputted from a reference arc length setter 15 and the electrical signals lS calculated and a motor control circuit 16 drives a motor 17 so that the deviation signal (e) is diminished to zero and controls the torch height EX so that the arc length (l) is made to the specific length.