Hzx
1
0UIFUT
MEASIJREMENTS
Uolts
and
decibels)
.
For output
measurements
introduce
completely
one of
the
leads
into
the
lower socket
marked
'
in ,o,r !1*9.? and
the
other
Iead into
0ne
of
the right
hand
side
sockets
also
marked
in
uuLuut
reo
,,10"i5,;;
"50
V-";
"250
Y
-"i
"1000
V-";
according
to
the range
required.
o
Hi',l,i['J.1iB'J',ll?,J,',i1",,'tL".ii.,jli
o'il';.1'*1'.i,]'iltlll[eii"T
l!t',';",fi,'i.3;
-
muy
le iniefied
in
the next
lowest range
in order
to
have a
more accurate
rea.lng.
tt ihould
be
borne
in
mind
that
{or the
measurement
of
power
in, dB,
the.^base
level has
0..-n
E[rn
is
iero
dB.
ifre- ,oO.in
'lnteinational
Standarii
is
in fact:
0 dB
=
1 mW at
600
ohms,
equivalent
t0 0.775
Volts
aciual.
0n
the scale
are
marked
directly
the dB
values
for the
range
l0 V
AC'..Using
the
range
z"v,'.ruiiuit--t+
og"riom-"ti'e
ieauing
observed.in
the-scale;
!:ln-c.lhe^-lalce
4
y:
irtiiui[--s-oa
trom
tne
ieioirig-otserveo"
in the
scale;
using
ihe ranges
50..and
100
V A'c''
itu'Ofi-reaaing
will
be that-obse-rved
increased
by 14
dB and
20 dB
respectively'
with
the
250
volt and
500
volt
ranges
A.C. add
28
dB and
34
dB respectively'
With
the
1000
Volt and
2000
Volt
ranges
A.C.
add
40
dB and
46
dB
respectively'
With
the
2500
Volts
range add
*
48
dB'
we
would like
to
explain
for
the
less
experienced
reader
the symbotic
value
of
dB.
lt is
t
;"r.i;;ir;
,iiiiit,ii.riit
ind
iherefore
can assume
any
value in aCcordance
with
the
reference
tor comparlson.
There
is a
relationship
with the
watts,
but
whereas.
these..represent
u.l aqlg!-te
quantity'
irl'J'ire-.in
travi
v-eri
f,rigi
viiues
ooih
positive
and
negative,
or
on
the,other
hand
very
iow
values
in accordince
with
the
terms
of
reference
which
have
Deen
cnosen.
ThedB,asaunitandasapsychophysicalquantity,.representingtheminimumyariationin
;;;r;ii;
;;*;iii,*ptiur.
io"il.
rir*in
eai,
but'lhis'variation
of
pouer
may
be of the
order
of
miiliwatts,
or' oi
*i[tr'*-itrlb,ji-.tang.s
of
the acoustic
perceition of the
variations
in dB.
3I
Diagram
how
to
use
the
Supertester
680
R for
frequency
measurements.
30
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