A technician is using a digital multimeter (DMM) set to the resistance () and continuity modes to troubleshoot de-energized components on an industrial electrical bench. Match each multimeter measurement reading on the left with its corresponding diagnostic circuit condition on the right.
- Probing across the terminal contacts of an unactuated, de-energized normally open (NO) control switch displays 'O.L' ().Normal high-resistance open-circuit state for separated contacts
- Probing between the main AC line power terminal and the metal equipment chassis of an isolated motor controller displays .Severe line-to-ground fault (dead short) to the chassis frame
- Probing across the isolated terminals of an electric motor stator coil rated at displays 'O.L' with no audible continuity tone.Burned-out internal open winding failure
- Probing across the unpowered filament terminals of an incandescent panel indicator lamp displays .Normal continuous, low-resistance conductive path for an intact resistive load
Answer
The normally open switch reading 'O.L' matches the normal open-circuit state for separated contacts; the AC line-to-chassis reading of matches the severe line-to-ground short circuit fault; the motor coil reading 'O.L' matches the burned-out internal open winding failure; and the indicator lamp reading matches the normal continuous conductive path for an intact resistive load.
Each multimeter reading directly correlates to the internal electrical state of the component: an open contact set produces infinite resistance ('O.L'), an unintended low-resistance connection between hot conductors and frame ground represents a dead short (), a severed coil wire destroys continuity ('O.L'), and a continuous resistive filament yields its nominal cold resistance ().
Step-by-Step Solution
Key Concept
Interpreting digital multimeter resistance and continuity display values (zero ohms, nominal ohms, over-limit / O.L) to distinguish between normal component states, open-circuit faults, and short circuits.
Estimated Time:1m 30s