Leader Electronics Corp. LDC-823A Instruction Manual - page 9
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Input sensitivity by duty ratio
With LDC-S23A, trigger level of Schmidt circuit is set in such a way so that it will
lYe
at
the maximum sensitivity against the signal of 50% duty ratio, such as sine wave, triangular
wave and rectangular wave.
When the duty ratio is reduced, the DC level of the signal added to Schmidt circuit will
vary as shown in Fig. 4-4-3 and it will not be able to exceed the lower limit of hysteresis
level so that the input sensitivity will be reduced.
-
-
Upper limit of
-
- - - - - - - - - - - - -
-
- - - - hysteresis level
DC level
Fig. 4-4-3
____
Lower limit of
hysteresis level
Duty ratio
=
X
100 (%)
to
Input sensitivity will be reduced in proportion to the decrease in the duty ratio. In the
case of LDC-S23A, when the duty ratio is 10%, input sensitivity will be approx. 1/5 com
pared to that with duty ratio being 50%.
Also, when the duty ratio becomes below 10%, the measurement may not be able to be
done even when input voltage is increased. This is due to the noise present, and the lower
limit will be about 10%.
4.5
Frequency measurement
Set the function switch to FREQ., apply signal to the input connector. The measuring range is
10Hz - 250M Hz. By setting the GATE time to the values shown in Table 4-5-1 and Table 4-5-2,
measurement can be done at the maximum resolution without overrange.
DIRECT MEASUREMENT (up to SO MHz)
Gate Time
Measuring frequency
Display
10
S
10Hz
-
9999.9999kHz
0.0100kHz
-
9999.9999kHz
1
S
10Hz
-
SOOOO.OOOkHz
0.010kHz
-
SOOOO.OOOkHz
0.1 S
10Hz
-
SOOOO.OOkHz
O.OlkHz
-
SOOOO.OOkHz
Table 4-5-1
PRE-SCALER (up to 250 MHz)
Gate Time
Measuring frequency
Display
10
S
10Hz
-
99.999999MHz
0.000010MHz
-
99.999999MHz
1
S
10Hz
-
250.00000MHz
O.OOOOlMHz
-
250.00000MHz
0.1 S
100Hz - 250.00000MHz
O.OOOlMHz
-
250.0000MHz
Table 4-5-2
In measuring the frequency of 10Hz - 1kHz at a high resolution, period-measurement is more
suitable.
8