Nassau Community College
Electronics and Telecommunications
Reference Sheet

Voltage Measurement Techniques


There two types of voltage measurements typically taken by a technician.  These are the voltage across a component and the voltage measured with respect to a reference point, most often ground.




Voltage Across A Component

The voltage across a component is measured by placing one probe on each lead of the component.  Two measurements are shown below.

To measure across a different component, both leads must be moved.
Across 1 Across 2
Measuring voltage across R10 Measuring voltage across R11




Voltage With Respect To A Reference Point

When measuring the voltage at a point with respect to a reference the common (black) lead of the meter always stays at the reference point, while the red lead is moved to the various points to be measured.  Two measurements are shown below.
Top of R11 to ground Top of R12 to ground
Measuring from the top of R11 to ground Measuring from the top of R12 to ground