9 ELECTRONIC INSTRUMENTS USED IN THE HEATING AND AIR CONDITIONING FIELD-NAMELY, COMBUSTIBLE GAS DETECTORS, CAPACITOR TESTERS, HALOGEN LEAK DETECTORS, HALOGEN MONITORING APPARATUS, INSULATION TESTERS, ALTIMETERS, DC CLAMP-ON VOLT OHM-AMMETERS, DIGITAL CLAMP-ON VOLT OHM-AMMETERS, DIGITAL ELECTRONIC THERMOMETERS, AC VOLTAGE DETECTORS, CONTINUITY/CAPACITOR CHECKERS, AC HIGH VOLTAGE DETECTORS, AND AIR BALANCERS