Amber 5500 - Relative Mode

Programmable
Audio Measurement
System
Section 2
If
desired,
this automatic
fime constant selec-
tion can
be overridden
using Special
Func-
tion
29.
A
further feature enhances
integration.
The
5500 uses a
proprietary process
called
Synchronous
Integration
that
yields
an
excel-
lent result to the usual
settling-time/ripple
compromise present
in AC level
measure-
ments. Under normal
conditions,
satisfactory
integration
of low
frequency
detection to
yield
acceptable
smoothness and
accuracy
also
implies
very long settling
time.
The
5500 avoids this
trade-off and is able to
yield
virtually
ripple
free
readings
within one
cycle
of the
input signal
-
a time
improvement
of
up
to an order
of
magnitude.
2.1.14
RELATIVE MODE
The
relative
mode allows the
current
measured value to
be
expressed
as
a ratio
(dB
or
%)
of a
stored
reference.
For
example,
signal
to
noise is the ratio of
noise to the
peak
or
program
level. Gain is the ratio of
output
level to
input
level.
Two
distinct
operations
must be
performed
to use
the relative mode.
First,
the
reference
must be
stored
(if
not
previously
done)
and
secondly,
the relative
mode must be
selected.
These two
operations
may
be done
in
any
order.
The
reference
may
be
stored in two
ways:
as
a
keyboard
entered value or as the
currently
measured value
(of
the
input signal).
To store a
relative
reference,
push
the REF-
ERENCE
prefix key
(bottom
key
in
the
column below
the RELATIVE
KEY).
Then
enter the
desired reference value
on the
Amber model
5500
Owner’s Manual Version
07
(a.
numeric
keys. Finally,
terminate the
entry
with the
dBm, dBV,
V
or %
keys
(note
that %
is a shifted
key),
for
example,
to enter a
reference
of
+8
dBm,
key
in:
—|a.
Or,
for a reference of
226 Volts :
mail)
a,
E
To
enter
the
presently
measured
value
simp-
ly push
the
“*”
key
after
the
prefix.
No ter-
minator is
required.
For
example,
to
set the
currently
measured
program
level as
the ref—
(
erence
(assuming
this value is
currently being
displayed
on the left
display)
push:
Having
thus stored a
reference,
the relative
mode can be
enacted
by pushing
the
RELA-
TIVE
key.
Absolute
readings
are
again
selected
by
a second
push.
The stored
refer-
ence is not
altered until a new
reference is
entered.
For
example,
assume a
reference of
+8
dBm
has been
previously
stored and the noise
level
being
measured
is
say
~65
dBm. If
the
RELATIVE
key
is
pushed,
the
reading
will
change
to
-73
dB
(the
ratio between
+8 and
~65).
When the
key
is
pushed again,
the
absolute
value of
-65
dBm
returns.
\/
2-12