HP 435B - Page 28

M od e l 435 Β

O p e r at i on
CA L C UL
ATI
N
G
ME AS
UREMEN T UN C ER TAI NTY
1 .

Ca l c ul ate t h e r eflect
i
o
n
coe
ffi
c i e
n t
fr o
m
t
h e g iv e n S
WR .
Po w er Sen so r
#1

Po w e r Sen so r #2

Po w e r So ur
ce
S WR = 1 .5

S WR = 1 .25

S WR = 2 .0
1 .5-1

1 :25-1

2 .0-1
ρι

1 .5+1

ρ 2

1 .25+1

Ps
=
2
.0+1
_0 .5

0 .25

_1 .0
2 .5

2 .25

3 .0
=0 .2

=0 .111

=0 .333
2 .

Ca l c ul ate t h e re l at iv e p o w e r a nd p er ce n tage po w e r mi s m atc h un ce rta in t
i
es fr o m t
he
r
eflect i on
coe ffi c i e n ts . An ini t i a l r e f e r e n ce l e v e l o f 1 i s ass um e d .
P
U
=

[1 ± ( ρ η ρ s )] 2
Ρυ l =
{1 ± [(0 .2)(0 .333)] } 2

PU, =

{1 ± [(0 .111)(0 .333)] } 2
= {1±0 .067} 2 =
11±0 .037}2
=

1 .067 1
2
a nd

10 .933 1 2

=

11.037 1 2 a nd 10 .963
1
2
= 1 .138 a nd 0 .871

=

1.075 a nd 0 .927
%v PU =

(PU-1) 100% ο
%v PU I =

(1 .138-1) 100% ο
=

(0 .138) 100% ο
= 13 .8% ο
%v PU , =

(1 .075-1) 100% ο
=

(0
.075) 100% ο
= 7 .5% ο
ρ
=
S WR -1
S WR +1
R e l at i ve P
owe
r
Un
ce r ta in t y
P e r ce n tage P owe r Un ce r ta in t y
a nd

(0 .871--1) 100% ο
a nd

(--0 .129) 100% ο
a nd -12 .9% ο
a nd

(0 .927--1) 100% ο
a nd

(-0 .073) 100% ο
a nd -7 .3% ο
F igure
3-6 .
Calculating M easurement U ncertainties
(1
of 2)
3- 1 1