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(~
Patch the circuit shown in Figure 22a and ground the input to
amplifier 14, or adjust potentiometer 1 to produce zero volt
(Figure 22b).
Adjust the PARALLAX potentiometer to produce
f(O) accurately.
This is best accomplished by connecting the
output of amplifier 16 to the VM jack, and using the voltmeter
in the NULL function (see Chapter II, Paragraph
3~.
(!0
Set the VDFG input to Xl (the first breakpoint).
Adjust the
CENTRAL SLOPE potentiometer to read f(X
l
) accurately on the
meter.
(£)
Set the VDFG input to X
2
(the second breakpoint).
Adjust
slope pot 1 until the meter indicates a null with the NULL POT
set to f (X
2
) •
NOTE
Except for the first two points, the
function value at a given breakpoint
is set by adjusting the slope pot for
the preceding breakpoint.
(SO
Continue in this way until all slopes have been set.
The
last value set is the right endpoint, XII' which is usually
+10 volts.
(~
Patch the circuit shown in Figure 21 (including, however, feedback
pot 17 as shawn in Figure 22a) , and plot the entire curve as
done prev"iously in Sub-paragraph (4)
(j).
(6)
Amplifier Overloads.
If the above procedure is followed carefully,
no overloads should occur during the set up of the breakpoints.
However, the set
up of the function values may cause overloads.
(If the desired function value is
close to 10 volts, it may be considerably more than 10 volts before adjustment.)
Of cour'se, if the function is properly scaled and is within the slope limitations
of the DFG, it should be possible to adjust the appropriate slope pot to set f(X)
to the desired value and remove the overload.
However, if the amplifier is saturated
it is hard to adjust the correct value, as the voltmeter will not respond immediately
to the slope pot.
In this case, the following steps are recommended:
(~
Temporarily patch an extra 10K feedback resistor around the
amplifier producing f(X).
(!0
Put the computer in the reset mode.
The output should not
overload.
(£)
Adjust the output to zero, or as close to zero as possible.
(~
Remove the extra feedback resistor.
The output should in-
crease, but not overload.
(~
Set the output to the desired value.
45
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