Application Note

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Application Note

Basic power quality

measurements on the

go with the Fluke 345

F r o m t h e F l u k e D i g i t a l L i b r a r y @ w w w . f l u k e . c o m / l i b r a r y

During your day-to-day

measurement activities,

there may be situations

where you need to know

more than what voltage or

current is present. When

that happens, the standard

clamp meter isn’t going to

get the job done. The solu-

tion may be a power quality

clamp meter such as the

Fluke 345.

The Fluke 345 combines

a clamp meter, power

quality meter, oscilloscope,

and data logger in one. This

combination of functions,

coupled with high quality

digital filtering, makes it

ideal for working with

variable frequency motor

drives, high efficiency light-

ing, and other loads using

switching electronics.

The basics

Of course, the Fluke 345 will make the basic mea-

surements of voltage and current to determine if

there is something seriously wrong with the circuit

under test. It’s rated for use at the service entrance

with a 600 Volt CAT IV rating.

Measuring voltage is as simple as using a clamp

meter: Connect the test leads up to the voltage

inputs, select voltage, and then read the rms volt-

age. Current measurement is just as easy. Select

current, open the jaw, clamp around the wire, and

measure. With the 2000 A range and large jaw

opening, you can evaluate most of the circuits in

the building.

The Fluke 345 can also measure both ac and dc

voltage and current simultaneously, and identify

the magnitude of each separately and combined

as ac+dc true-rms. That’s helpful for checking a

UPS, battery, and output, to make sure that the

circuits are working correctly and the batteries

are in good condition. A dc voltage component

on the output of a UPS, or even an adjustable fre-

quency motor drive, may even be a quick indicator

of a developing problem. For example, waveform

non-symmetry will cause an apparent dc voltage

component and may indicate impending failure of

system output electronics.

Summary of content (4 pages)

PAGE 1
Basic power quality measurements on the go with the Fluke 345 During your day-to-day measurement activities, there may be situations where you need to know more than what voltage or current is present. When that happens, the standard clamp meter isn’t going to get the job done. The solution may be a power quality clamp meter such as the Fluke 345. Application Note The Fluke 345 combines a clamp meter, power quality meter, oscilloscope, and data logger in one.
PAGE 2
Waveform view Harmonics The world runs on ac voltage, be it at home, shopping center, hospital, factory, or industrial complex. Sometimes valuable troubleshooting information can be gained by “viewing” the ac waveforms behind the action. Turn the Fluke 345 switch to and you can view the voltage and current waveforms. From there, select either of the waveforms and use the arrow keys to measure voltage at a specific point on the waveform, as well as the time between two points on the waveform.
PAGE 3
The waveform in Figure 3 would only exist in a perfect world, without harmonics. Since that’s unlikely to exist it’s more often that something similar to the the distorted waveform in Figure 4 will be present. Figure 5. Current for an electronic load. Figure 3. Clean sine wave. Using the Fluke 345, you can view waveforms, and, more importantly, distortion measurements and even the level of individual harmonics. The screen in Figure 6 shows a view of individual harmonics.
PAGE 4
Power measurements Logging Power measurements—Watts, VA, VAR, Volts, Amps and Power Factor—are the mainstays of any system analysis. The Fluke 345 reads these parameters in both single-phase and balanced three-phase power systems. Taking these measurements will help determine circuit loading, so you can judge whether it’s safe to add more load or if a new circuit is required. These parameters are essential for investigating and correcting low power factor, the culprit behind high utility bills.