1 : onboard LM358 chips; 2 : 100 times gain circuit design; 3 : onboard 10 k adjustable resistance, adjustable magnification ; 4 : onboard power light; 5 : chip has led the main pin, can directly input and output signals; 6 : working voltage: 5 ~ 12 v ; 7 : board size: 32.7 (mm) x13.3 (mm);