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Application Note

The NEW Fluke

and T

PRO

Electrical Testers

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

The first electrical tester had a simple solenoid that

pulled an indicator attached to a spring across a spe-

cial voltage scale. The higher the voltage applied to

the solenoid, the further the indicator would be pulled

against the spring.

High accuracy is not a big concern when installing

lighting, switches, and other common electrical wiring

and equipment. Often, you just need to differentiate

common voltages from one another.

The problem is, these classic testers are no longer

safe to use by NFPA electrical measurement stan-

dards. Many companies have outright barred them

from the field and floor.

Since the basic measurement need was still there,

Fluke developed two new testers that did what elec-

tricians needed them to do. The new T+ and T+PRO

ac/dc electrical testers are rated to CAT IV 600 V

and CAT III 1000 V and use light, sound, and vibration

to indicate voltage. They also test for continuity and

GFCI and are low impedance. Additionally, the T+PRO

model has a LCD digital readout screen, a rotary

phase indicator, and resistance.

And, on the T+PRO, a digital

readout of either measurement

will appear on the LCD. If the

batteries fail, the LEDs will still

light up, so that the user always

has voltage detection capability.

Both testers measure ac and dc

voltage from 12 to 600 volts (the

T+PRO measures down to 10.2 V

on the LCD). For the residential

electrician, the T+ model covers

all of the basic electrical mea-

surements, from voltage entering

the house at the power panel,

to the output of the transformer

powering the doorbell.

One typical use is checking

a 240 V ac outlet for a dryer or

range for correct wiring. Place

the tester’s probes between the

two hot sockets of the outlet. The

tester will automatically come

Basic voltage

applications

Before starting any test, touch

the two leads of the T+PRO or

T+ together. All of the LEDs

should light up. That means the

tester is working and has battery

power.

These testers have nine LEDs,

each of which indicates a spe-

cific voltage, that illuminate

when the test leads contact

voltage. At the same time, the

testers beep and vibrate strongly

enough that you can feel it when

voltage is detected. For ac volt-

age, the ac LED lights up and the

beeper makes a chirping sound.

For dc voltage, the dc positive

or negative LED lights up and

the beeper makes a steady tone.

on, illuminate the LEDs to indi-

cate 240 V ac, beep, vibrate, and

illuminate the hazardous voltage

LED. Next, check for 120 V ac

between each hot and neutral

socket of the outlet.

For industrial techs, check volt-

age balance between phases—is

it within 2 %—and for voltage

drop across motor contactors

or relays, where voltage drop

should be negligible. Also check

control circuit voltage. To elimi-

nate measurement errors from

ghost or stray voltages, these

testers’ low input impedance

loads the circuit and absorbs any

ghost voltage energy. That gives

you a reliable indication that the

circuit you are testing is truly

dead.

Summary of content (3 pages)

PAGE 1
The NEW Fluke T+ and T+PRO Electrical Testers Application Note The first electrical tester had a simple solenoid that pulled an indicator attached to a spring across a special voltage scale. The higher the voltage applied to the solenoid, the further the indicator would be pulled against the spring. High accuracy is not a big concern when installing lighting, switches, and other common electrical wiring and equipment. Often, you just need to differentiate common voltages from one another.
PAGE 2
When measuring ac voltage between phases of a threephase circuit, the T+PRO tester indicates the phase relationship between the two test leads as well as the voltage. A typical application is connecting a three-phase motor and testing for proper rotation direction. Connect the tester’s leads between two of the phase conductors. The tester’s display will indicate a clockwise rotation ( ) when the red test lead voltage is 120° ahead of the black lead.
PAGE 3
Five reasons to give up your old solenoid tester 1. In the US, a useful solenoid tester can measure up to 480 V or more. Having the ability to measure higher voltages limits the tool’s ability to detect voltages below 100 V, due to the poor dynamic range of its magnetics. Try using one on 24 V or 48 V control circuits, and you may as well be using a stick of wood. 2. Solenoid-based testers can appear on the circuit under test as a load and interfere with its operation.