HVACR UNIT 33

Besides the normal electrical functions found on general-purpose multimeters, what additional functions are common on multifunction meters intended for HVACR use?

Temperature, microfarads, and frequency

Where does the current come from for resistance measurements on an ohmmeter?

The battery inside the meter

An ohmmeter is set on continuity and beeps when the leads are connected to a circuit. This indicates that:

The circuit path is complete.

What could happen to an analog meter if a voltage is tested that exceeds the setting on the meter?

The meter can be damaged.

What part of an analog scale gives the most accurate reading?

The midpoint of the scale

With its leads on either side of a switch, a voltmeter reads 120 V. This indicates that:

The switch is open, so voltage cannot pass through.

One advantage of digital meters is:

There is no need to interpret the scale.

How are clamp-on ammeters used?

They are clamped around one of the power wires feeding the circuit.

How are inline ammeters connected to read the current in a circuit?

They are connected in series with the load.

Before attempting to use an electric meter to measure the circuits on a system, the technician should:

Understand how the unit and the meter work.

When checking to make sure a circuit is de-energized, you should test:

Voltage to ground.

Which of the following can multimeters be used to measure?

Voltage, current, and resistance

How are voltmeters connected to read the voltage drop across a load in a circuit?

Voltmeters are connected in parallel with the load.

Meter functions commonly used for air-conditioning troubleshooting include:

Volts, amps, and ohms.

When is it important to match the polarity of the meter leads to the polarity of the circuit being tested?

When reading DC voltage

This test instrument reads current in an electrical circuit.

Ammeter

Root-mean square (RMS) is a mathematical formula for:

Calculating the electrical power passing through a alternating current circuit.

What category of electric meter is intended only for measurement inside an appliance?

Category I

What category of electric meter is intended for measurement at the electric meter base?

Category IV

A technician uses an ohmmeter to check resistance and for a complete path in the electrical circuit, also known as:

Continuity.

What is the operating principle of an analog voltmeter?

Current passes through a coil, which creates magnetism that moves a needle.

A wattmeter is connected to a circuit with 120 V, 10 A, and a power factor of 91.7%. Its reading is:

1,100 W.

What should you look for on the meter besides a CAT rating?

A certification from an independent laboratory

What type of meter do HVACR technicians use to measure current?

A clamp-on ammeter

What is a transient voltage?

A momentary surge or spike of voltage that can be several times the normal circuit voltage

Which of the following systems would be most likely to produce a power waveform that would require a true RMS meter to accurately measure?

A three-phase motor controlled by a variable-frequency drive

When choosing an electric meter, it is important to use the proper category rating:

For both the meter and the leads.

The range of an electric meter describes:

How low and high the meter will read for each function.

What is a common application for data logging instruments?

Identifying intermittent problems

How does a weighted average meter measure alternating current?

It takes an average over a short period of time.

Capacitance meters measure the capacitance in a circuit or in a start capacitor. This is measured in what unit?

Microfarads

What type of measurements require a true RMS meter to obtain accurate results?

Nonlinear, electronic switching loads

What scales on analog meters require battery power to operate?

Only the ohms scale

Wattmeters read true power in a circuit. This can be expressed by what equation?

Power = amps × voltage × power factor

What three specifications help determine whether or not a particular meter is appropriate for a particular use?

Range, resolution, and accuracy

How can a technician determine what the proper PPE is for a particular application?

Read NFPA Standard 70E.

The safest way to use a meter while testing for voltage is to:

Rest the meter on something; do not hold it.

When measuring voltage with an analog meter, what should the technician do?

Set the meter to the highest range.

When using a meter with a manual scale setting, always:

Start with the highest scale and work down to get an accurate reading.