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Trimming adjustments mayor may not be necessary, depending upon the nature
of the function and the accuracy required.
As with a ten-segment unit,
trimming should be done from the origin outward.
Remember there is one
function value that cannot be trimmed:
the PX and CS pots allow the func-
tion to be set properly at x
=
0 and at
~
of the two breakpoints nearest
the origin; the value at the other breakpoint will be close to the desired
value, but it cannot be changed without disturbing previous settings.
If it is necessary to trim the function values at the two breakpoints near
the origin accurately, an iterative procedure may be used.
Trim the func-
tion value nearest to zero by means of the PARALLAX pot, trim the other value
by means of the CENTRAL SLOPE pot, and alternate until both function values
are correct.
The value of f(O) is, of course, no longer equal to the tabu-
lated value, but the values at the two breakpoints are correct.
The inter-
action between settings means that after setup, the value of f(O) may no
longer be exactly collinear with the adjacent values.
Now proceed to trim
the other function values, working from the origin outward, as before.
After the last function value is set, be sure both SEGMENT SELECTOR switches
are off, and plot the function using the time-base integrator in the MDFG
setup drawer.
A sweep from -reference to +reference should be used to cover
the entire range of the function.
If one of the breakpoints occurs at x
=
0, then the procedure is somewhat
simplified.
The zero breakpoint can be set on BPI for either the
+
or
the -DFG; the BPI pot on the other DFG is not used, since this segment is
used for CENTER SLOPE.
The value f(O) is set by a PARALLAX pot as usual;
the value at "breakpoint lit on the DFG being used to give the zero break-
point shou\d agree with the PARALLAX setting.
8-23
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