Troubleshooting a DMM's 7-segment display that occasionally skips digits A digital multimeter's seven-segment display sometimes fails to show certain numbers. What is a safe and effective test procedure to identify a defective segment?

Introduction / Context:
Intermittent missing numerals on a seven-segment readout usually point to a single weak or open segment. A controlled bench test that individually drives segments helps you separate a defective LED segment from a driver or interconnect problem.

Given Data / Assumptions:

• The DMM display is a seven-segment package (likely multiplexed).
• Segments can be driven individually for test with proper polarity and current limiting.
• We want a procedure that isolates the display from the rest of the circuit.

Concept / Approach:
By applying a known test voltage to each segment (through an appropriate series resistor to limit current), you directly verify whether the LED segment illuminates. If a segment fails to light when correctly driven, the display module is suspect. If all segments light reliably, the fault likely lies in the driver IC or multiplexing circuitry.

Step-by-Step Solution:

Verification / Alternative check:
If all segments pass, reconnect the display and probe the driver outputs during normal operation. A logic probe or oscilloscope will reveal missing drive pulses due to a faulty driver or bad solder joints.

Why Other Options Are Wrong:

• Remove and diode-check (A): Impractical and may mislead due to internal multiplexing; also risks damage.
• Tie all segments to Vcc (C): Forces “8” but does not isolate a single bad segment versus driver faults.
• Slowly increase DMM supply (D): Varying entire supply is not a targeted segment test and may stress the instrument.

Common Pitfalls:

• Forgetting the series resistor, which can overcurrent and damage the LED segment.
• Applying reversed polarity on common-anode versus common-cathode modules.

Final Answer:
Apply 5 V directly to each segment (with proper current limiting) and replace any segment that does not light.