Abstract: Circuit testers used with digital logic and its associated components are described. The circuit testers better protect the user, better protect the equipment, and provide testers in a form that is easy and safe to use. The tester includes a body member with a hand guard or hand protector and that includes a trigger switch, a fuse housing, a probe, and a second lead connector. All components are rated for at least the maximum voltage and current expected for the device. The hand guard serves as a physical barrier to any exposed voltages. The trigger switch provides for secure placement of the test lead and probe before energizing the circuit or component. To protect the equipment being tested, the maximum desired current to the test location can be identified and a properly-sized fuse installed in the fuse housing, protecting the existing equipment being tested from further damage by excessive currents.