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8-12
8.4.3.8
The Pattern of Settings.
Notice that except for the
first and last setting, the value of y at any point is determined by the
setting on the previous slope pot.
The reason for this is explained in
Paragraph 8.4.2.
Note also that BP pot 1 is not set; it is not used in
ten-segment operation.
This means that position 1 on the SEGMENT SELECTOR
is skipped (see left-hand column in Table 8.2).
8.4.3.9
Slope Switch Position.
The table says to "set y on a
pot and switch".
Each slope pot has a slope switch immediately to its left;
when setting the function value, the operator first turns on the switch to
the +SL or -SL position, and then adjusts the pot to obtain the correct
f(x) value.
If the switch
is~the
OFF (center) position, the pot has nq
affect.
To determine whether to use the
+
or - position, leave the switch off while
depressing the readout button.
This displays the function value with the
segment turned off.
This value will not be equal to the desired value at
this point.
Tu~ng
the segment on will increase or decrease this value.
If the desired function value is more positive than the value with the seg-
mentoff, then the switch should be turned to the +SL position.
Conversely,
if it is desired to decrease the function value (make it more negative),
then the -SL position should be used.
Some computer operators prefer not
to memorize this rule, but simply turn the switch on in either direction;
if the output moves in the wrong direction, the switch should be reversed.
In any case, it is the direction of change that is important; the function
value should change in the right direction when the switch is turned ono
If the switch has no effect on the function value, the slope pot is probably
set to zero; give it a few turns and repeat the ON/OFF process.
8.4.3.10
Trimming Adjustments.
Having set up the entire func-
tion, from the origin outward, the operator. should now go through the table,
again, checking the funtion values f(x).
The breakpoints, once set, should
remain essentially constant, but the function values may- have changed slight-
ly.
This is because the value at a given breakpoint is set by changing
the slope at the previously set breakpoint, causing a small shift in the
previously set function value.
The amount of this shift depends upon the nature of the function and the
spacing of breakpoints, but it is generally about 0.0010 to 0.0020 unit
(10 to 20 millivolts), and rarely greater than 0.0050.
In many cases, this
shift is negligible.
However, if desired, most of this effect may be re-
moved by a series of trimming adjustments o These adjustments should be made
in the same order as the original setup - starting at the origin and working
outward.
The trimming process goes much faster than the original setup,
since the breakpoints do not have to be set again, and only small changes
in function values are required.
After trimming, most function values will
be correct to within 0.0002 to 0
0
0005 unit; rarely is a second set of trim-
ming adjustments needed.
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