HP 435B - Page 80

S ERV IC E S HEE T 2 (Cont' d )
An in c r ease d n o i se l e v e l m ay b e ca u
se d by C1, C6 o r C30 l i n e
n o
i
se filters .
R an
ge-to- r a n ge i nacc ur ac y b et w ee n t h e
100
m
W r an ge a nd
a n ot h
e
r r
an ge m a yb e du e to α s ha pin g c ir
c
ui t d ef
ect .
R
ange Switc h
R
a n ge-to- r a n ge in acc ur ac y w hi c h i
s
ca u
se
d
by t h e RAN G E
s wi tc
h
atte nu ato r sca n easily be i so l ate d by p
e rf o rmin g o n eof t h e
In
st rum e n tat i o n A ccur ac yP e rf o rm an ce
T
ests
(r ef er to Sect i o n
IV)
.
T
h ir d
Amplifier
Ad j u st t h e
C AL ADJ co n tr o l fro m i ts pr ese n t sett in g to
t h e εεω
sto p . Th e n ad j u
st t
h
e co n tr o l to t h e εω sto p . Th e m ete r r
ea din g
will n o rm
a lly c han ge by ±2 dB (>4 dB fr o m sto p
to sto p ) . Th e ac
v o l tage at ΤΡ
4 will c
h
an ge fro m t h e n o min a l sett in g
to a ppr o xi-
m ate ly
-35% ο (cc w sto p ) a nd +70% ( εω sto p ) .
Sync h ronous Detector
Th e ph ase c h a n
geof t h e 220 Hz s i gna l b et w
ee
n
t h epo w e r sensor's
sa mplin g gate
a nd t h e S yn c hr o n o u s D etecto r
ca nn ot b e m ea-
s ur ed dir ect ly b
eca u se t h e d etecto r ou t pu t i s
do r at h er t han ac .
H o w e v e r , t h e ph ase
diff e re n ce at ΤΡ 4 (t h e inpu
t to t h e d etecto r
c ir c ui t)
can
b e m eas ur
e d . B ecau se t h e ph ase c han ge b
etwee n ΤΡ 4
a nd t h e d etecto r
i s
kn
o wn, t h e ph ase re l at i o n ship
betwee n t h e
driv e s i g n a l ( ΤΡ 7)' a nd
t
h
e ΤΡ 4 s i gn a l indi cates t h
e tota l ph ase
s hif t t hrou gh t h e
ac
a mplifi
e r s . Thi s is t h e ste p - by -ste ppr
oce dur e
f o r c h ec kin g ph ase s hif t .
α .

Set t h e P owe r
M ete r a nd (if u se d ) t h er an ge
ca
libr
ato r con-
trols as s h o wn in t h
ege n er a l t ro ubl es h oot in g inf
o rm at i o n abo v e .
b . Co nn ect t h
e osc
ill
osco p e's v e r t i ca l inpu ts to t h e
220 Hz
d r iv e ( ΤΡ 7) t hr o u g h
α
divid
e- by -te n pr obe (C h a nn e l Β ) a nd to ΤΡ
4
t hr ou ghα o n e-to-o n e
pr o
b
e (C h a nn e l Α ) .
ε .

Set t h e osc ill
osco
p e co n
t r o l s as f o ll o w s : C ha nn e l Α se n s i t iv -
i t y to 0 .05 V / divi s i on w i t h
ac co uplin g, C ha nn e l Β se n s i t ivi t y to
0 .2 V / divi s i o n, h or iz o n
ta
l
s
w
ee p to 0 .5 m s/ divi sio na nd t h e
dis-
play m o d e to Ch
a
nn e l Α
a nd Β , c h o pp ed wi t h t ri gge rin g fro m Β .
d .

Ad j u st t h e
v
ert i
ca
l p
os i t i o n co n t r o l s un t il b ot h t r aces
a r e
s ym etr i ca l wi t h r es p
ect to t h e h o riz o n ta l ce n te r lin e (r efe r
to t h e
t ypi ca l w a v e fo rm b
e
l
ow) .
e .

Set t h e t im
e b ase m ag ni fie r co n t ro l to Χ 10 . Th e h ori zo n
ta l
sca l e i s now 50
As/division (r efe r to t h e e xp a nd e d wa vefo
rm
b e l ow) .
Troubles h ooting
B loc k Diagram

,
S ERV IC E S HEE T