Measurement guides that protect the meter and the technician
Practical, safety-first measurement procedures: how to use a multimeter, measure voltage, current, resistance, continuity, voltage drop, test relays, batteries and alternators.
How to Use a Multimeter Safely and Correctly
A digital multimeter is the basic instrument of electrical work: it measures voltage, resistance, continuity and current...
How to Measure Voltage with a Multimeter
Voltage is a difference in electrical potential between two points, so it can only be measured across something. The met...
How to Measure Current with a Multimeter or Clamp Meter
Current is the rate of charge flow, so it is measured through the circuit, not across it. That single fact drives every...
How to Measure Resistance with a Multimeter
Resistance is measured with the circuit dead and the component isolated, because the meter supplies its own small test c...
How to Test Continuity (and What a Beep Really Proves)
A continuity test asks one question: is there a conductive path between these two points? The meter answers with a tone...
How to Measure Voltage Drop Under Load
Voltage drop is the voltage lost across a connection, cable, switch or ground path while current is flowing. It is the s...
How to Test an Automotive Relay
A relay uses a small control current through a coil to switch a much larger current through a separate set of contacts....
How to Test an Automotive Battery
A battery test has to answer two different questions: how much charge is stored, and how much current the battery can ac...
How to Test an Alternator and Charging System
The alternator converts engine rotation into electrical power and must hold the system voltage above the battery’s resti...
How to Diagnose a Grounding Problem
The ground path is half of every circuit. When it develops resistance, the symptoms look like almost anything: dim light...
Before you measure
- Use a meter rated for the category and voltage you are measuring. A low-voltage meter on a high-energy circuit is dangerous.
- Verify the meter on a known source before trusting a “no voltage” result.
- For mains, industrial and EV high-voltage work, isolate, lock out and prove dead. Work only within your qualification.