Testing a zener diode with basic instruments From a maintenance perspective, is it workable to use an ohmmeter to perform a quick in-circuit or out-of-circuit check of a zener diode’s basic health (shorted/open and forward-junction behavior)?

Introduction / Context:
Technicians often start with simple instruments. An ohmmeter (especially the diode-test mode on digital multimeters) can quickly identify obvious faults in semiconductor devices. For zener diodes, a simple check can verify forward junction behavior and detect gross shorts or opens even though it cannot measure the zener breakdown voltage.

Given Data / Assumptions:

• Zener diode under test removed from circuit or isolated.
• Digital multimeter with diode/ohms function.
• Goal: basic go/no-go test, not precise zener voltage characterization.

Concept / Approach:
In forward direction, a zener diode behaves like a standard silicon diode (about 0.6–0.7 V drop). The diode-test mode should show a forward drop and a high resistance in the reverse direction at the meter’s low applied test voltage. A shorted zener will show low resistance both ways; an open will show high resistance both ways. Measuring the actual zener breakdown requires a supply that exceeds the rated zener voltage, which an ohmmeter does not provide.

Step-by-Step Solution:

Verification / Alternative check:
To confirm regulation, build a simple test with a current-limiting resistor and a DC source greater than the zener voltage, then measure the stabilized voltage across the device.

Why Other Options Are Wrong:

Common Pitfalls:
Testing in circuit without isolation can give misleading readings through parallel paths; confusing diode-test mode with true breakdown measurement.

Final Answer:
Correct