A method for color correction is provided. The ultrasonic bonding machine includes a support structure configured to support a workpiece during a bonding operation. The controllably conductive media changes its impedance when an external stimuli such as an applied electric field is imposed thereon. The novel battery pack has built-in safeguards against dangerous LiPo battery conditions and is implemented in a small, portable unit which contains the battery cells, control and protection circuitry, internal charger and display gauge.