Leader Electronics Corp. LDC-823A Instruction Manual - page 8
-2-1. In the case that
ator is lighted, push
the display shows as
nnec
t the ground
_
he positive hot side
e
maximum allowable
values are as follow:
)c.
When the input
are the maximum
below.
k when connecting
t pulses of flyback
.uld be damaged by
) these circu its.
'
proximately 30pF.
ce becomes 100pF
influenced by this
)f the device under
e
operation of the
-lA
Setting of input sensitivity
(
1
)
Input sensitivity and noise
The input sensitivity of LDC-823A can be selected from 0.02Vrms, or 0.2Vrms, in order
to measure input signals of wide voltage ranges. When a large signal is applied to the
input at the higher input sensitivity, the noise included in the input signal may induce
miscounting. In this case, reduce the input sensitivity to the appropriate input range as
listed in Table 4-4-1. This minimizes errors.
In pu t sensi tivi ty
Range of input voltage
0.02Vrms
0.02
-
0.2Vrms
0.2Yrms
0.2
-
2Vrms
Table 4-4-1
(
2
)
Method to prevent the interfering noise from outside
(3)
The maximum input sensitivity of LDC-823A is approx. 15 mVrms, so it might be pos
sible to mis-attribute even if the noise voltage of about 45mVp-p is present. Attention
should be paid specially when spike-like noise from the AC power supply is accumulated,
as the value indicated in this case shall be about 30Hz over the actual value.
In order to preven t such mis-a ttribution, it is required to provide the shield at the con
necting section to the circuit to be measured or to the circuit itself so that the noise from
the AC power supply or the devices outside shall not accumulate. It is also required to
reduce the impedance of the test point under test. There is hardly any trouble in the case
of 500,/750, line, however, in the case of 6000, employed in the audio frequency band,
the spike-like noise may accumulate, so it is required to provide the sufficient shield.
Measurements of Modulated Signals
Fig. 4-4-2
VH
VH:
Input Sensitivity of
counter
As seen in the above Fig. 4-4-2, in order to measure the frequency of modulated
carrier-wave, if the voltage of highest modulated part is greater than the input sensitivity
YH (0.02Vrms), it is then possible to count the carrier-wave .
...... 7 .....
.