The
input
frequency
f is applied
to
a Voltage Comparator
which
pro-
duces
the
square wave signal
a.
When
this
signal is at
OV
the capaci-
tors C are being charged to the ref.
voltage
of
-lOV.
A charge 0 is
now
available
on
the
capacitors, and a
moment
later a dis-
charge is stated by means of
the
signal
C.
Each charge 0 supplies a certain
current
into
the Integrator and
the
total
current
will
be
proportional to the frequency f.
Lin.lLog
Converter
When
the
instrument
is in Log position, a
Lin.lLog
converter is inserted
between
the
tuning
potentiometer and the VCO.
As
it
appears
from
the simplified diagram, a
number
of transistors are
connected
in
a
row
with
a reference voltage applied to
the
bases. This
reference
voltage is increased
by
approx.
0,5
V steps up
the
row,
and
the transistors
will
now
be
turned
on
as
the
Lin.
input
voltage is in-
creased.
In
this
way
a a parabolla is formed like
shown
on
the
diagram, yet hav-
ing
18
steps instead of 3,
thus
providing a good approximation
to
a
true
log curve.
In connection
with
the Lin
.I
Log Converter, a
temperature
compensating
circuit
is used.
V342
is acting as a temperature detector as
the
forward
voltage across
it
is
temperature
dependent. The voltage drop across
V342
is amplified by
V357,
the
resulting
signal being present across
R356.
By means
of
R342
+
355
is
now
to
the
Linear
input
voltage added a volt-
age
which
is proportional
to
the
forward
voltage across
V342
and
thus
temperature compensated.
a
-IS,4V
b
-IOV
a
c
-IS,4V
+ref.
Lin
5.75
Valid from serial no.
523774
Technical Description
1023.1
Lin
input
Log
t----
.....
---
..
Log
out
1-3
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