HP 435B Service Manual

O p e r at i o n

M od e l 435 Β
Cal F actor Switc
h
R esolution
E rro r . Th e r eso lu t i o n

Sp ecified U ncertai n ties . Th e s p ec i fi e d un ce r ta in-
o
f
t
h
e C
ALFA
C
T
O
R s wi tc h co n t ribu tes α s i g nifi-

t i es whi c h acco un t f o r p a rt of t h e tota l po w e r m ea
ca
n t
e
rr o r to t h e tota l m easur e m e n t b ecause t h e

s ur e m e n t un ce r tain t ya
r
e :
s wi tc hh as 1% ste p s . Th e m a ximum e rr o r poss ibl e
in eac h p os i t i o n i s ±0 .5% .

α .

In st rum e n tat i o n +-1% 1 o r ±0 .05 dB .
3-7 .

Corrections for E rror
Cal i b rat i on F actor and E ffective E fficiency . Th e t w o

c .

C ALFA
C
T
O
R s wi tc
h r
eso lu t i o
n,
0 to ±0 .5% ο
co rr ect i o n f actor s b as i c to p owe r m ete r s a r e ca li-

(d e p e ndin gon Ca
l F
acto
r ) .
brat i o n f actor a nd e ff ect iv e e ffi c i e n c y . Eff ect iv e
e ffi c i e n c y i s t h e co rr ect i o n f acto r fo r RF l osses

d .

Z e ro set, ±0 .5% ο o f
full
sca
l
e o
f l
o w est
r
a n ge
w i t hin t h e p owe r se n sor . Ca libr at i o n f acto r ta k es

wh
i c h i s 15 n W .
in to acco un t t h ee ff ect iv ee ffi c i e n c yandmi s m atc h

e .

Z e r o Ca rry o v e r, ±0 .5% .
l osses .
Ca libr at i o n f actor i s expr esse d as α p
e
r ce n tage
w i t h 100% ο m ea nin g t h e p owe r se n so r h as no
l osses . N o rm a lly t h e ca libr at i o n f actor will b e
100% ο at 50 MHz, t h e op e r at in g fr e qu e n c y o f t h e
in te rn a l re fe r e n ce osc ill ato r .
Th e p owe r se n so rs u se d wi t h t h e P o w e r M ete r
h a v e individu a lly ca libr ate d ca libr at i o n f acto r
c urv es pl ace don t h e ir co v e r s . To co rr ect f o r RF
a ndmi s m atc h l osses, s imply find t h e p o w e r se n -
so r 's ca libr at i o n facto r at t h e m eas ur e m e n t f r e-
qu e n c y fr o m t h ec urv eor t h e ta bl e t h at i s s upplie d
wi t h t h e p o w e r se n so r , a nd set t h e C ALFA CTOR
sw i tc h to t hi s v a lu e .
Th e C AL FA C
T
OR s
wi
tc
h r eso lu t i o n e rr o r o f
±0 .5% m ay b e re du ce d by o
n
e o
f t h
e f
o ll
o
wing
m et
h
o d s :
1)

Set t h e C AL FA C
T
OR sw
i
tc
h
to t
h
e
n
ea
r est
pos
i
t i o n s abov e andb e l ow t h e co
rr
ect
i
o
n f
acto
r
g iv e n on t h e ta bl e . In te rpo l at in g b et
w
ee
n
t
h
e
po w e r l e v e l s m easur e d pr ovid es t h e cor r ecte
d
p owe r l e
v
e
l .
2) Lea
v
e
t h
e C AL
FA
CTO R s wi tc
h
on 100%
a
fte r
ca
libr at i o n . Th
e
n, m
ak e t
h
e
m easur e m e n t
a nd r ecord t h e r eading .
U
se t h e r eflect i o n coe ffi-
c i e n t, m ag ni t ud e an d ph ase an g l e, if s u c h α ta bl e
i s s uppli e d w i t h t h e po w e r se n so r , to ca l c ul ate t h e
co rr ecte d p owe r l e v e l .
3-8 .

Calculating W
orst Case
U ncertainty
b .

Po w
e
r r
e
f
e
r
e
n ce
±0 .7%
o r
±0 .03 dB
.
f .

N o i se a nd
Drif
t,
d
e p e
nd
s on t
h
e
r
a
n
ge a nd
t yp e o f
se
n so r .
g
. Ca
libr at i o n f acto r un certain t y, w hi c h
d
e pe
nd s
on se
n sor t yp
e,
i s li ste d in t h e se n so r
m a nu
a
l .
Fi g ur
e 3-5 g
iv
es an
exa mpl e o f s p ec ifi e d un ce r-
ta in t y ca
l
c
ul
at
i o n .
Calculating M ismatc
h
Un
certainty . Mi s m
atc
h
un-
certainty
i s t h e r es ul t o f t h e source mi s m atc h
in te r act in gwi t h t h e po w erse n so r mi s m atc h . Th e
m ag ni t ud e o f un ce r tain t y i s r e l ate d to t h e m ag ni-
t ud es o f t h e so ur ce and po w e r se n sor r eflect i on
coe ffi c i e n ts, whi c h ca nb e ca l c ul ate d fr o m S W R .
Fi g ur e 3-6 s h o w s h o w t h e ca l c ul at i o n s a r e m ad e
a nd Fi g ur e 3-7 illu st r ates mi s m atc h un ce r tai n t y
a nd tota l ca l c ul ate dun ce r ta in t y f o r two cases . In
t h e fi r st case, t h ep owe r se n so r 's S WR =1 .5, a nd in
t h e seco nd case, t h e powe r se n so r 's S WR =1 .25 . In
b ot h cases t h e so ur ce h as anS WR o f 2 .0 . Th e
e x ampl e s h o w s t h e e ff ect on po w e r m easure m e n t
acc uracy α poo rly m atc h e d po w e r se n so r will h ave
as co mp a r e d to o n e wi t h l ow mi s m atc h .
Α f aste r , eas i er wa y to fi nd m i s m atc h un ce r tain t y
i s to u se t h e HP Mi s m atc h Err o r (unce r tain t y)
Limi ts/ R eflecto m ete r Ca l c ul ato r . Th e ca l c ul ato r
m ay b e o b ta in e d, on re qu est, fr o m your n ear est
H e wl ett- P ac k a rd o ffi ce by u s in g HP part numb e r
5952-0948 .
W or st case un ce r
ta in
t y i s t h e s um of t h esp ec ifi ed

Th e m et h o d of ca l c ul at in g m eas ur e m e n t un ce r-
un ce rtain t i es a nd mi s m atc hun ce r tain t y . Un ce r-

ta in t y fr o m t h e un ce r tain t y in dB i s s h o wn by
ta in t y ca l c ul at i o n i s ou t lin ed in t h e f o ll o win g t w o

Fi g ur e 3-8 . Thi s m et h od w ould b e u se d wh e n t h e
s ub sect i o n s a nd e x a mpl es are wo rk e d o u t in Fi g-
ini t i a l un ce r tain t y ca l c ul at i o n s w e r e m ade w i t h
ures 3-5 a nd 3-6 . F o r α m or e co mpl ete expl an at i o n

t h e Mi s m atc h E rr o r / R eflecto m ete r Ca l c ul ato r .
of m easur e m e n t un ce r tain t y re fe r to HP a ppli ca-
t i o nn ote AN-64-1 "Fund a m e n ta l s o f RF a nd M i-

' R ef er
to In st rum ent accu
r ac y s p ec i f i catio n in Sect i on Ι w h e nu s in g t he
c r owa v e P o w e r M easur e m ent" .

to p two ra n ges .
3- 2

HP 435B Specifications

General

Brand	HP
Model	435B
Category	Measuring Instruments
Language	English