Electrical BasicsTest & Measure

Basic Electricity

Basic components of an electrical circuit.

Switch

LoadGround

Hot

Neutral

What is AC & DC

• “AC” stands for Alternating

Current “DC” stands for Direct Current

• AC is denoted by the the words “AC” or the symbol

• DC is denoted by the words “DC” or the symbol

• The majority of applications are AC

Ohm’s Law

V = I x Rvolts = amps x resistance

Electricity is made up of voltage, current, and resistance.

Using the analogy of water flowing through a hose:Voltage is the pressure at the ends of the hose.Current is the water flowing through the hose.Resistance is the diameter of the hose (wire).

Basic Electricity

Typical Measurements• Current

– 1 amp is equal to 1000 milliamps

– 1 amp is equal to 1,000,000 micro amps

– 1 milliamp is equal to .001 amps

– 1 micro amp is equal to .000001 amps

• Milli is depicted as a lower case m in front of the symbol– i.e. mA or mV

• Micro is depicted as a µ in front of the symbol– i.e. µA or µV

Symbols

Basic Electricity

V – Voltage

A – Current (in amps)

Ω

Hz

NCV

F°/C°

– Resistance (in ohms)

– Frequency

– Non-Contact Voltage

– Temperature

– AC Voltage

– DC Voltage

– Capacitance

– Continuity

– AC & DC Voltage

– Diode Check

• Voltage is the amount of electrical force (pressure) it takes to push current (electrons) through an electrical conductor (wire).

• Voltage can be either “AC” or “DC”. (Alternating Current or Direct Current)

• Voltage is what is typically measured at an outlet or electrical box.

Typical Testers Used For Detecting or Measuring Voltage

Dual Lead Probes

Non-Contact Probes

V = I x RVolts = amps x resistance

Digital MultimetersSolenoid Tester

Typical Application

An appliance or piece of equipment is not working or an end-user wants to install a new wiring device so they want to find out if voltage is present.

What is Voltage?

V AC Voltage

Typical application types:

• Household Outlets, Switches, Doorbells, panels, circuit breakers

• Heating elements, Security Systems

Check for energized circuits and verify proper voltage in typical home applications.

Why? Incorrect voltage can cause improper operation or premature failure of electrical devices. For example, a home that has a voltage of 137 volts may burn out ceiling fan motor. Alternately, too little voltage can cause failure as well.

Symbols

Typical application types:• Automotive Testing• DC Motor Controls• Batteries

Check for proper voltage in automotive and industrial circuits. DC is found more in industrial applications than residential.

Why? Incorrect voltage can cause improper operation or premature failure of electrical devices. Just as with AC Voltage, too much or too little voltage can cause heating issues within motors and other electric components.

DC VoltageV

Symbols

• Current is the amount of electrons flowing through a circuit. (1 Ampere = 6.5 billion-billion electrons-per-second flowing through a wire)

• The measurement of current is stated in “Amps” or “milli-Amps (mA)” (1000th of an amp).

• Current can be either “AC” or “DC”. (Alternating Current or Direct Current)

• Current is typically measured with a clamp meter

Typical Tester Used For Measuring Current

V = I x RVolts = amps x resistance

Digital Clamp Meter Typical Application

A circuit breaker keeps on tripping so an end user wants to find out the amount of amps being used by an appliance, light fixture or piece of equipment.

What is Current?

Typical application types:• Circuit Board Testing• Power Supplies; In-Rush Current• Circuit Breaker Panels

Verify that the current draw does not exceed the maximum value of the component.

Why? Too much current can cause heating issues that will reduce the life of electric and electronic components. For example, an incorrectly wired fan motor’s life may be reduced by 50% if there is too much current draw.

AC/DC CurrentA

Symbols

• Resistance is the amount of “friction” in a wire or circuit. • Resistance is stated in Ohms• Resistance is most commonly measured using a multimeter set to

the Ohms position • Continuity is a circuit with very low resistance and this is typically

tested with a continuity tester or digital multimeter.(a wire that has a break in it does not have continuity)

Typical Testers Used For Measuring Resistance / Continuity

Continuity Tester

Digital Multimeters

V = I x RVolts = amps x resistance

Voltage/Continuity Testers

Typical Application

A user wants to test if a fuse is blown or if a power cord is good and does not have a break in it.

What is Resistance?

Ω Resistance

Typical application types:• Ground Circuits• Resistor Value Verification• Circuit Board Testing

Check the resistance values of outlet grounds or resistors found on circuit boards. Measurement is in Ohms.

Why? Too much resistance may cause stray current to find another path to ground. For example, a receptacle ground wire incorrectly connected may cause excess heating in the ground wire.

Symbols

Typical application types:• Switches, Outlets, Extension Cords, fuses, and heating coils• Unenergized Low Voltage Wiring

Check for a continuous circuit.

Why? Verify the status of fuses, extension cords, and other types of wiring. For example, landscaping lighting is typically buried around gardens. Digging may actually cut a wire, rendering the circuit useless.

Continuity

Symbols

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