Since the ramp begins at a negative offset, each voltage measurement consists
of
clocking the duration
of
a
pair
of
ramps. The first ramp is generated with the Voltmeter Input Selector set
to
the grounded input (input
0).
The duration
of
this ramp is proportional to the offset.
The
second ramp
is
generated with the selector set
to
the input
to
be measured. The duration
of
this ramp
is
proportional to the input level plus the offset. The
difference in duration is computed by the Controller and is proportional to the input voltages.
The large negative offset voltage permits the
DC
Voltmeter to measure both negative and positive voltages.
8B-50
To Next Page
Loading...
