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Electronics Engineering QUESTION #11744
Question 1
A DMM on resistance range is connected to a powered circuit (even a low-voltage one). The consequence is:
  • The circuit provides reference current improving measurement accuracy
  • Possible damage to the DMM's internal reference resistors and false readings✔️
  • The DMM auto-ranges to the current mode safely
  • No effect — modern DMMs are protected against up to 1000 V on all ranges
Correct Answer Explanation
A DMM in resistance mode applies its own internal current source (~0.5–1 mA) through the internal reference resistors. Applying external voltage while in resistance mode causes excessive current through the precision resistor network, producing false readings and permanent damage to internal components. Always de-energise and discharge circuits before resistance measurements.