Graymark 803 - INSTRUMENTATION AND MEASUREMENT; Electrical Safety Precautions; Transformer Voltage Test

RUMENTATION
&
MEASUREMENT
: zie
about
to
perform LIVE
VOLTACE
TESTS
on
yoLtr
actoard
circuit.
Remember
that,
when
properly
used,
-:icity
is a useful
servant
of
man,
but
when
misused,
::.icity
is
very
dangerous
and
can
cause
severe
bodily
t. Therefore,
always
use
case
when
working
with
elec-
,'l,
and observe
these
ru/es.
:'tc!ug
circuit
from
power source
EEFORE
changing
::eier /eads
or wiring.
:-;e on/y
one
hand
when
performing
tests.
-(:and
on an
insulated
sttr{ace
when
working
on
and
test-
'rg ihe
breadboard
circuit.
'i
at'ailable,
use
an
isalation
transfc:rmer
for added
safety'
i,l=ep
the breadboard
on
a
wooden
ar ungrould-1d
sur;
-:ce
rvhen
working
on
or testing
the
circuit.
NEVER
work
-^
a metal
surlace.
--
'\'K
SAFETY.
-
1. Voltage Test
For this test
you
will
need a volt-ohm-milliammeter
(VOM).
The
purpose
of
this test
is to demonstrate
the voltage step-down action
of transfgrmer
T1
by
measuring
and comparing
the
primary.
and secon-
dary
voltages.
--a.
Adjust
the
VOM to a
range
that
will measure
-
-e.
UNPLUC
THE LINE
CORD.
-
-f
. Next, connect the
VOM
test
probes
to tacks
-'l
and 2 so
you
can measure the voltage
between one side of the secondary
winding
and the center-tap.
PIug in
the
Iine
cord.
Read and record this voltage
(Ect
1) in
the
space
provided
in Fig. C.
lt should be ap-
proximately
25 volts
AC.
g.
UNPLUC
THE LINE CORD.
-h.
,\4ove the
VON,1
test
probe
from tack
1
to
tack
3
so
you
can
measure
the
voltage be-
tween the other side of
the secondary
wind-
ing
and the center-tap.
Plug in the
line
cord.
Read and
record
this
voltage
(Ect
2) in
the
space
pr"ovided in Fig. C.
lt should be the
same
as fct 7.
-
-i.UNPLUG
THE LINE CORD.
Remove the
VO,\4 test
probes from
the
breadboard.
-j.
Refer to
Fig.
G and add
Ect-1 to Ect
2 and
. ls this volt-
record their sum
age about the
same as Es?
It should
tie.
Have
instructor initial
your
Progress
Cuide.
Adjust
the
VOM
FIG.
F
125 iolts AC, then,
connect the test
probes
to the
primary
,.vinding
Iugs
(A&B)
oI
T1,
as shorvn
in l-ig F.
b.
Plug
the
line cord
into a 1-l,0-120
volt re-
ceptacle.
RearJ ancl
recorcJ this
primlr;
voltage
(Ep)
in
thc space
provided in Fig.
C.
tt
shoulC
be approximately
115 volts
AC.
c. UNPLUC
THE LINE CORD.
d.
Move the
VOLI test
probes to tacks
1 and 3
on the breaciboard
so
you
can
measure the
seconclarr.,r,oltage.
PlLig in the
line cord.
Read and
record the secondary
r,oltage
(Es)
in
the space
provided
in Fig. C"
It shoulcl
be approxtnlzlsltl
50 volts
AC.
PRIN4ARY SECONDABY
Ectr:-1
c-
LP-
-
FIG,
G
E5
'-
9