Push Button Switch Testing: How To Check Switch Quality With Multimeter

Step-by-step power-off operation to diagnose damaged push button contact faults

Malfunctioning push buttons are a frequent cause of equipment startup failure, jog loss or emergency stop breakdown. You can test switch health quickly with a multimeter continuity mode. Always cut off the whole power supply before testing to avoid electric shock or instrument damage.
For a normal NO push button, resistance stays infinite and the buzzer stays silent without pressing. When pressed, the circuit conducts and resistance approaches zero. If it fails to conduct while pressed, internal contacts are burned out. If it conducts without pressing, contact adhesion occurs and the switch needs replacement.
For NC push buttons, the buzzer sounds at rest and stops when pressed. Composite buttons require separate inspection of two contact groups. At rest, NC terminals conduct while NO terminals disconnect. When pressed, NC contacts open first before NO contacts close. If two groups conduct or disconnect simultaneously, the switch is defective. Visual inspection also helps. Replace switches with cracked housing, black oxidized contacts, stuck buttons or burned terminals directly.