Table of Contents
Advertisement
t
t
B
f
+ -
0
2
B
f - -
0
2
B
1 + - -
2 f
0
B
1 - -
·
-
2 f
0
if B is small compared with- f
0
then
t
=:= K
_!!__
fo
As t x f is constant, i.e. T
=
K' /f
then at the frequency f
0
t
KB
T
=
K"'
If the requirementS
~BIT
is satisfied, that is, that t
~T.
then no error
due to rate of scan is obtained on the RMS value of the component. Also a
scanning speed which is faster than that which would be available on aT
constant programme, may be used.
However, if a faster scanning speed than will satisfy the requirement
S
~BIT,
is selected, the relative error on a component is only dependent on
j;
Therefore the relative error is constant, and the
difference
in level
measured in dB between the different components will be the same, as if the
requirement had been satisfied. For example, in distortion measurements
where relative values are required, this will give the true value of distortion,
but
not
the true individual value of each component.
9.2.3. 8 variable
This programme (position 1 on the B & T PROGRAM selector) allows the
ratio B/f to be kept constant at the switchover frequencies. See Table 5. 1.
The preceding calculation shows that the time spent on one given com-
87
Advertisement
Table of Contents
