(4) Connect d.c. voltmeter across test points
turning R18 clockwise.
If a hunt
1 and 2 (1 is positive). Adjust R11 and R1
develops, re-adjust R16 for stability. If no
for zero volts at 60 cycles (or 50 cycles).
hunt develops, apply and reject load to
Repeat adjustment until voltage across
check for stability under transient
test points 3 and 4 and 1 and 2 is zero
Assuming that no hunt
volts and frequency is 60 cycles (or 50
develops for increase in frequency gain
cycles) with no load on the engine. If test
(R18, CW) or that the hunt can be
points 1 and 2 cannot be zeroed, they
removed by re-adjustment of feedback
must be reduced to a minimum.
(5) R12 should be adjusted to give about 5
R18 and note transient performance.
volts across test points A and B. If this
Finally, a position may be reached where
voltage is too low, response will be
no readjustment of the feedback gain R16
sluggish and if it is too high, a rapid
oscillation may be caused. Exact value
R18. Then reduce the frequency gain to
will depend upon engine characteristics.
the stable region and optimize stability
Normal range is from 4.5 to 6 volts.
and performance with the feedback gain
(6) R15, the load measurement gain control,
(It is recommended that the
is adjusted for optimum transient
frequency gain be reduced to a point
performance. Fully clockwise position is
where the system is not on the edge of
maximum load measurement gain.
instability for long term stable operation).
Transient performance improves as the
gain) should be set as far clockwise as
frequency gain R18 is a minimum for that
possible and R16 (feedback or stability
particular position of frequency gain
gain) set as far counterclockwise as
adjustment. For any particular position of
possible without causing an oscillation for
the frequency gain R18, there is an
any setting of R15. Where sensitive
optimum position of feedback gain R16.
frequency recording instruments are
If the feedback gain is reduced too much
available the adjustments of R15, R16
(R16 too far CCW) there will be
and R18 can be adjusted for the desired
insufficient feedback to stabilize the
transient shape to meet desired
operation at steady state. If instability is
specifications of time and frequency
reached (a slow oscillation in comparison
deviation. The value of capacity at C8
with another to be mentioned) turn R16
(fig. 127) also affects the transient
clockwise until stability is reached. This is
frequency response. Smaller values of
the optimum setting for that level of
capacity will give faster response;
frequency gain. If R16 is turned too far
however, if C8 is too small the system will
clockwise, a very fast oscillation (faster
than the oscillation mentioned above)
(8) Increasing the load measurement gain
may occur. Turn R16 counterclockwise to
R15 (clockwise direction) will improve
the optimum point previously mentioned.
performance; therefore, it
This faster oscillation may not be
should be adjusted as high as possible.
apparent from the sound of the engine or
The adjustment of R18, R16, and R15 are
observation for the frequency instruments.
interdependent. For any position of R18,
Visual observation of the throttle
there is an optimum position for R16.
movement is recommended.