The isoltest hd 93 holiday detector is a portable quality control inspection instrument used to electrically locate defects pinhole in protective coatings applied to metallic structures.the detector converts low voltage direct current (rechargeable batteries) into regulated high voltage pulses. output voltage is selectable from 2,5 to 30 kvolts in 7 settings and wave form frequency are calibrated on compliance on applicable international standard. this adaptable unit can be used on both large and small diameter pipe as well as flat surfaces when such surfaces are coated with a high electrical resistant material and the surface beneath the coating is electrically conductive; is the right tool for the detection of imperfections on protective coatings applied to pipelines, tanks, pilings or any similar structures; each unit is supplied with a calibration report and ce compliance certificate. the isoltest hd 93 holiday detector is versatile, durable construction for all field conditions, light weight, easy battery access.