Chapter 5 - Section 1 Understanding and testing power and Power Devices

Receptacle Tester

A device used for testing wall sockets.

Power Strip

A group of sockets the connect to a single AC outlet. This allows for multiple devices to share a single receptacle as an outlet. Maximum watt rating is applied to power strips (3000 watts is a decent amount)

Multimeter

A handheld device that can be used to measures amps and impedance, or test the voltage inside the computer. Has one black lead and one red lead.

Voltage

A representation of the potential energy. Measured in volts(V)

Spike

A short transient in voltage that can be due to a number of thins such as a short circuit; tripped circuit breakers; power outage; or lightning strikes.

Joules

A way to measure energy. Generally, the more Joules, the better. For computer systems, 1000 Joules or more is recommended.

Surge Protectors

Also called a Surge Suppressor. A power strip that incorporates a MOV to protect against surges and spikes. Usually measured in Joules. Higher-quality surge protectors have multiple MOV's for the different connections and for the individual wires in an AC connection.

AC

Alternating Current. The flow of electrons alternates.

Sag

An unexpected decrease in the amount of voltage provided. Generally limited in time and the severity of the decrease.

Surge

An unexpected increase in the voltage provided. It can be large or small.

120 V AC

Associated with home outlets

5 V DC

Associated with some of the internal components of your computer.

DC

Direct Current. The flow of electrons is one way.

MOV

Metal-Oxide Varistor. A device that protects against surges and spikes.

Volt-Amps vs. Watts

Most times there is virtually no difference. In this case though, there is a difference. The volt-amp rating will be slightly higher due to the difference between apparent power (when in battery backup mode) and real power (when pulling regular power from an AC outlet).

Voltage Detector

Pen shaped device that beeps when it comes into contact with voltage.

Testing an AC outlet step 1

Place the black lead in the ground socket.

Testing an AC outlet step 2

Place the red lead in the hot opening.

Brownout

Power decreases to the point that the lights dim and computers shut off.

Testing Ground Wires With Multimeter

Same steps as testing an AC outlet with a multimeter, except that you connect the black lead to the round wire and the red lead to the neutral wire. Should read 0 V.

SPS

Standby UPS. This is a cheaper version of UPS that might have a slight delay when switching from AC power to battery power. This delay might cause errors in the computers OS.

Impedance

The amount of resistance in c circuit. Measured in ohms.

Type B AC outlet

The most common AC outlet. Also called a wall socket, electrical receptacle, or power points.

Amperage or Electrical Current

The movement of electrical charges. Measured in amps(A)

Wattage or Electrical Power

The rate of electrical energy in a circuit. Measured in watts(W)

Volt-Amps

The unit used to measure UPS devices' output power capacity. Also measured in watts.

Reasons for Dirty Power

Too many devices on the same circuit, power coming from the electrical panel or the municipal grid fluctuates, the panel or grid is under/overloaded.

Removing Multimeters

Turn off the multimeter, remove the red lead, and then remove the black lead.

Testing an AC outlet step 3

Turn on the multimeter to test the volts AC. Should hover around 115 V to 120 V.

UPS

Uninterrupted Power Supply. A device that regulates the output of AC to the computer. Takes a Surge Protector and combines it with a battery backup. Protects the computer not only from surges and spikes, but also from sag and brownouts.

Varistor

Variable Resistor. Every time a surge or spike happens, a part of the Varistor is burned out. The higher the Joule rating, the longer the Varistor can last.

Dirty Power

When the voltage fluctuates between amounts. Ex: fluctuating between 113 V and 121 V.

Blackout

When there is a total loss of power. There is a second problem that can occur with blackouts, and that is a power spike when power is restored.

Clean Power

When you get a steady amount of voltage.