Astro Pneumatic Digital LCD 3-48V Wide Range Circuit Tester 7764 The Astro Pneumatic Digital LCD 3-48V Wide Range Circuit Tester 7764 is used to check electrical circuits and accessories on all 3-48 volt systems. Needle-sharp stainless steel probe allows for easy piercing and small, ergonomic design for easy use in confined areas. Computer Safe with Backlit LCD display for accurate voltage readouts. For use on cars, boats, trailers, vans, RVs, motorcycles, airplanes and snowmobiles.