Ectron 441A, Инструкция по эксплуатации, Страница: 42 / 74

wheel rides on the engine shaft that has spacing irregu-
larities. This causes a slight variation in the output pulse
spacing and would produce noise in the resulting analog
output of the Model 441A. This noise would prevent
knowing the exact rpm. If the wheel has 40 cogs, using
a
PULSES / REV
olution setting of
040
would elimi-
nate the noise caused by the spacing irregularities.
Therefore, using digital averaging allows the output to
be as exact as the inherent high accuracy and stability
of the Model 441A.
SELECTABLE INPUT SENSITIVITY
This control adjusts the gain of the input amplifier and is useful when noise is causing
erratic triggering. This can occur when no signal is present or when the signal level is low.
Usually, the optimum setting of this control is made in conjunction with the input filter
setting. Gain decreases by a factor of approximately 6:1 from the
MAX
setting to the
MID
setting. A further decrease of approximately 8:1 occurs between the
MID
setting and the
MIN
setting.
RESPONSE TIME
Response to an abrupt frequency change is 0.005
s
+
1
⁄
f
new
with the output filter set to wide-
band (f
new
is the new frequency). Thus, if the input frequency is 10 Hz and suddenly changes
to 1000 Hz, the analog output will assume the new value in less than 6 ms. For lower filter
frequencies,
5
⁄
f
co
(in seconds) must be added.
UPDATE RATE
The update rate is 1 ms or
1
⁄
f
in
, whichever is greater.
Figure 4-8
Filter Circuit for ABS Testing
Applications Model 441A
4-12