Leader Electronics Corp. LDC-824 User manual

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1. Introduction
LDC-824° LDC-824S
DIGITAL COUNTER
LDC-824(S) is a digital frequency counter/timer designed to measure the frequency and period
of a signal, featuring a wide frequency range (10Hz—520MHz), a high input sensitivity (20mV rms),
and high resolution to 8 digits. The period function makes the unit outstanding for video tape re-
corder service applications. This instrument can be used for adjustment, test and repair of audio
instruments, AM/FM radios, TVs, CB radios, computer clocks, amateur-radios, electronic watches,
musical instruments, etc. The LDC-824(S) is small and portable. A big bright fluorescent display
assures easy readability of values. The green display does not induce eye fatigue even after an extended
period of viewing. Readout miscounts are reduced by zero-blanking, unit-display (kHz, MHz, ms) and
overrange display. The use of LSI and MSI in the internal circuit assures reliable performance and less.
power consumption.
2. Specifications
Frequency Measurements
Range
Gate time
Resolution
Accuracy
Period Measurements
Range
Multiplication Factors
Resolution
Accuracy
Input Section
Input sensitivity
(MQ)
(502)
Attenuator
Coupling
Input impedance
Maximum input voltage
(1MQ)
(502)
10Hz — 80MHz (direct), 50MHz — 520MHz (pre-scaler)
0.1s, 1s, 10s
10Hz,
1Hz,
0.1Hz
(direct),
100Hz,
10Hz,
1Hz
(pre-scaler)
+1 count + time base accuracy
100ms — lus
X10, X100, X 1000
10pus, lus, O.1pus
+1 count + time base accuracy + trigger error
20m Vrms (10Hz — 80MHz)
50m Vrms (80MHz — 520MHz)
20mVrms (100kHz — 80MHz)
50m Vrms (80MHz — 520MHz)
1, 1/10
AC
Switchable 1MQ and 502.
10Hz — 400Hz : 100Vrms
400Hz — 100kHz : 20Vrms
100kHz — 520MHz: 5Vrms
100kHz — 520MHz: 5Vrms

Time base
LDC-824(S)
Frequency
Accuracy
Clock out
External clock
General Specifications
Display
Ope rating tempe rature range
Power source
Power consumption
Dimensions
Weight
Accessories
10MHz (OVEN)
+1x10~% (tlppm) (32°F — 104°F)
(0°C — 40°C)
Regular Option
1Vp-p 10MHz 1Vp-p 1MHz
1Vp-p — 10Vp-p 1Vp-p — 10Vp-p
8 digits, 7 segment fluorescent display overflow indication,
gate indication and zero blanking
0°C — 40°C (32°F — 104°F)
100V, 117V, 200V, 234V + 10%
50Hz — 60Hz
(Voltage-change is accomplished by change on tap of trans-
former)
Approx. 12VA, Approx. 18VA (with optional)
74(H) X 200(W) X 250(D)mm
Approx. 3’(H) X 8”(W) X 10°(D)
excluding knobs and legs
Approx. 2.6 kg Approx. 2.8 kg (with optional)
Approx. 5%|bs. Approx. 6% lbs. (with optional)
Clip cable with BNC connector

3
3
PANEL FUNCTIONS
“Ae Front Panel
an
(eo)
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et
ea
(S20niie)
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3-1 shows the front panel of LDC-824(S).
Power switch:
To turn on, depress push-button, to turn off, again depress push button.
GATE TIME; MULTIPLIER SELECTOR:
For frequency measurement, this switch is used to change GATE TIME; when in the
_period-measurement mode, it is used to change the multiplier factors. Each range is as
follows:
GATE TIME: 0.1, 1 and 10 sec.
MULTL: xX 10, X 100 and X 1000
RESET Switch:
By pressing this switch, the counter stops its operation. When released, the display is cleared
to zero. After a delay of approximately 0.1s, if there is an input signal, the counter starts
counting.
|
Function Selector:
A push button switch for changing the measurement mode is used for selecting the
measurement
functions
of
PERIOD
and
FREQ.
|
FREQ. RANGE Selector:
Selector for DIRECT MEASUREMENT (10Hz — 80MHz) and PRE-SCALER (50MHz —
520MHz).

(6) SENSITIVITY Selector:
Push button switch for 20mV, 200mV, respectively.
7) IMPEDANCE Selector:
Selector for input impedance of 1MQ and 50Q.
(g) INPUT Connector:
el
Put a signal in to measure.
(9) Handle/Stand combination:
l
ot
-
pes
youd
The lock of the handle can be released by pressing the mounted part of the handle on bo
sides with both hands. The handle can then be freely rotated. When th
is locked.
QQ Unit Indicator:
For frequency measurement, the indicator shows “MHz” at 520MHz 1
at
80MHz
Freq.
Range.
‘ms’
is
displayed
in
the
case
of
period
measurements.
QD Display:
It is a 8-digit, 7- -segment, fluorescent display. In accordance with the measuri: 1g Tange,
decimal point is displayed automatically, and the leading zeros are blanked.
G2. GATE indicator:
Displays the opened or closed state of the GATE. When GATE is open, indicator is lit.
(3 OVERRANGE indicator: :
Lights when the frequency is over the counting capacity of 8 digits. In the case of
overrange,
push
the
GATE
TIME/MULTI.
selector
to
smaller
values
until
the
overrange
indi-
cator light goes of f
4
3.2 Rear Panel:

4.2
©)
SSOE68
Ss)
OUTPUT/INPUT Terminal:
Output
and
input
terminal
for
a
clock
signal.
When
the
selector-switch
for
internal
and
external
(INT/EXT)
is
on
INT,
the
internal
clock
is
available
to
the
terminal.
Feed
a
clock
to
the
terminal
externally,
when
the
selector
switch
is
on
EXT.
Serial number label
Power cord
Rubber feet
Fuse holder (contains 0.3A fuse)
INT/EXT Switch:
Selector switch of an internal clock and an external clock.
With a screw driver, trimmer control adjustments of the reference frequency oscillator can
be made. For procedure, refer to section 6 — Maintenance.
Operating Instruction
Precautions in use
(1)
(2)
(3)
(4)
(5)
In
connecting
the
instrument
to
the
device
(to
be
tested),
particularly
in
an
internal
connection,
remove
all
AC
power
to
the
device,
and
remove
the
cord.
After
discharging
all
charged
capacitors,
connect
the
cable
for
measurement,
thus,
the
danger
of
an
electrical
shock
can
be
minimized.
Take
the
same
care
in
disconnecting
the
input
cable.
.Use AC-power source of LDC-824(S) at 50 — 60Hz, within 10% of rating voltage.
Caution:
Excessively
large
or
small
AC
voltages
may
induce
erroneous
operation.
In replacing the fuse, use the designated 0.3A fuse.
Avoid
all
the
severe
mechanical
shocks
to
crystal
oscillator
or
fluorescent
indicators.
Reference
clock:
Wait
about
20
minutes
for
correct
measurement
until
the
crystal
oscil-
lator gets stable in aging.
Fundamental Operation
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Disconnect the input cable of the LDC-824(S).
Connect the AC power cord to the proper AC power source.
Set POWER switch to the ON position.
Set the function switch to FREQ.
Set
the
SENSITIVITY
selector
to
20mVrms.
Put the GATE TIME Selector at 0.1S.
When
FREQ.
RANGE
Switch
is
80MHz
and
520MHz,
Display
reads
0.00
kHz
and
0.0000
MHz
respectively.
The
GATE
indication
is
lighted
for
0.1s
while
the
gate
is
open,
and
disappears
for
0.1s
while
the
gate
is
closed.
Set GATE TIME Selector at 1S.
Display
shows
0.000
kHz
at
80
MHz
and
0.00000
MHz
at
520MHz.
GATE
indicator
re-
peats
to
1s
light
on/0.1s
light
off
alternately.
Press the 10S GATE Selector
Display shows 0.0000 kHz at 80 MHz and 0.000000 MHz at 520MHz. GATE indicator
repeats to 10s light on/0.1s light off alternately.

(9)
Set
the
FUNCTION
switch
to
PERIOD.
(10)
Use
the
“MULTY”’
scales,
and
confirm
the
display
as
shown
in
Table
4-2-1.
In
the
case
that
the
displayed
figure
shows
other
than
0
(zero),
oF
when
GATE
indicator
is
lighted,
push
the
reset
switch,
then,
GATE
indicator
disappears
(gate
is
closed),
and
the
display
shows
as
in
Table
4-2-1.
a
ee
a
ce
DO
Table
4-2-1
(11)
In
the
above
6—10
OVER-flow
indicator
always
shows
light
off.
4.3
Input
Connections
Connect
BNC
Connector
of
the
accessory
cable
to
the
input
terminal.
Connect
the
ground
—
negative
side
of
the
clip
to
the
common
of
the
device
under
test.
Connect
the
positive
hot
side
to
the
test
point.
The
input
is
AC
only
(DC
blocked
by
0.1MF
capacitor).
The
maximum
allowable
voltage
of
the
AC
component
of
the
input
signal
depends
on
frequency.
The
values
are
as
follow:
Input
Impedance
IMQ
10Hz
—
400Hz
100Vrms
or
280V
p-p
400Hz
—
100kHz
20Vrms
or
56Vp-p
50
100kHz
—
520MHz
5Vrms
or
14Vp-p
100kHz
—
520MHz
5Vrms
or
14Vp-p
The
maximum
voltage
of
the
DC
component
of
the
input
signal
is
+
100V
DC.
When
the
input
signal
is
not
a
continuous
sine-wave
or
is
modulated,
the
following
values
are
the
maximum
allowable
AC
input
voltages
permitted
in
accordance
with
the
frequency
chart
below.
Input
Impedance
TMQ
10Hz
—
400Hz
250V
p-p
AQ0Hz
—
100kHz
56Vp-p
500
100kHz
—
520MHz
14Vp-p
100kHz
—
520MHz
14Vp-p
CAUTION
NOTE:
Caution
should
be
taken
not
to
get
an
electric
shock
when
connecting
or
removing
the
input
cable.
High
voltage
circuits
and
horizontal
output
pulses
of
flyback
transformers
in
TV-sets
generate
excessive
voltages.
The
LDC-824(S)
could
be
damaged
by
exceeding
input
limitations.
Therefore,
never
make
a
direct
connection
to
these
circuits.
The
input
impedance
of
this
instrument
is
approx.
1MQ
and
shunted
by
approximately
30pF.
The
input
cable
has
a
distributed
capacity
of
approx.
7OpF.
As
the
capacitance
becomes
100p
F
in
total,
it
is
not
recommended
for
such
a
circuit
or
a
device
under
test
as
influenced
by
this
capacitance
to
be
measured.
:
Note:
Do
not
connect
the
input
of
LDC-824(S)
to
a
high
impedance
point
of
the
device
under
test.
The
parallel
effects
of
this
1M2/100pF
combination
affect
the
operation
of
the
circuit
being
tested.

4.4 Setting of input sensitivity
(1)
Input sensitivity and noise
The
input
sensitivity
of
LDC-824(S)
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.
0.02Vrms 0.02 — 0.2Vrms
0.2 — 2Vrms
Table 4-4-1
Automatic Trigger Level Function
The trigger level of LDC-824(S) is designed to function automatically in 80MHz frequency
range. |
Trigger level is set automatically to a level (Fig. 4-4-2) of input voltage that is divided
equally into three parts. The functional range of automatic trigger level shall be, for
instance, between 20mV and 200mV input voltage when preset sensitivity is 20mV. When
it is preset at 200mV, the input voltage range for automatic trigger level is between 200mV
and 2V. In the case the above-mentioned input voltage range is exceeded, the trigger level
is fixed at 200mV position when preset at 20mV sensitivity and is fixed at 2V position
when preset at 200mV sensitivity.
In accordance with all these, correct signal counting can be conducted (Fig. 4-4-2) without
miscounting when noise voltage is 50% or less of the signal voltage and it is within the
range of automatic trigger level.
In addition, measurement of pulse signals with large duty ratio can be conducted with
ease, as the trigger level is set automatically at the optimum level, even if it has been
necessary to adjust the trigger level for the pulse signal measurement.
Positive Peak
Noise
Upper Trigger Level
Lower Trigger Level
Input Signal
Negative Peak
Shaped Signal FLL.
Fig. 4-4-2

(3) | Measurements of Modulated Signals
{lye nell Ds
UT de
|
al
i
al Ve
VH: Input Sensitivity of
counter
As
seen
in
the
above
Fig.
4-4-3,
in
order
to
measure
the
frequency
of
modulated
Modulated signal
carrier-wave,
if
the
voltage
of
highest
modulated
part
is
greater
than
the
input
sensitivity
VH
(0.02Vrms),
it is
then
possible
to
count
the
carrier-wave.
4.5 Frequency measurement
Set
the
function
switch
to
FREQ.
and apply
signal
to
the
input
connector.
The
measuring
range
is
10Hz
—
520MHz.
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 80 MHz)
Gate
Time
Measuring
frequency
Display
10
S
10Hz
—
9999.9999kHz
|
0.0100kHz
—
9999.9999kHz
1S
10Hz
—
80000.000kHz
|
0.010kHz
—
80000.000kHz
0.1S
10Hz
—
80000.00kHz
0.01kHz
—
80000.00kHz
Table
4-5-1
PRE-SCALER
(up
to
520
MHz)
Gate Time Measuring frequency Display
10
S
10Hz
—
99.999999MHz
|
0.000010MHz
—
99.999999MHz
1S
0.00001MHz
—
520.00000MHz
0s
Table 4-5-2
In
measuring
the
frequency
of
10Hz
—
1kHz
at
a
high
resolution,
period-measurement
is
more
suitable.
4.6 Period measurement
(1)
Set
the
function
switch
to
PERIOD,
and
apply
the
signal
to
the
input
connector.
The
measuring
range
is
100ms
—
0.001ms
(1us).
Period
measurement
is
suitable
for
accurate
measurement
in
the
frequency
range
of
10Hz
—
1kHz.
By
setting
the
MULTI.
and
PERIOD
as
listed
in
Tables
4-6-1
and
4-6-2,
more
accurate

measurements can be accomplished within a short time and longer numerical display
measurement results in a more accurate measurement.
When the measuring time is within 1s — 0.1s,
1ms — 0.1ms 1.0000ms — 0.1000ms
Table 4-6-1
When the measuring time is within 10s — 1s,
Dipl
10Hz — 100Hz 100ms — 10ms X100 100.000ms — 10.000ms
100Hz — 1kHz X1000 10.0000ms — 1.0000ms
Table 4-6-2
(2) | Measuring accuracy
The accuracy of period measurement can be expressed as follows:
Accuracy = +1 count + trigger error + time base accuracy . . . Equation 4-6-1.
‘ In the above equation, the most important factor is the trigger-error. Trigger-error occurs
with the overlapped signal noise and noise in the counter. During the measurement, when
the display fluctuating range is within +1, the error can be regarded as +1 count. If it is
over +1 count, it may be trigger-error or alteration of the input signal. As a checking
method, when the input sensitivity of counter or input voltage is set to higher values, if the
variable range becomes less, it can be judged as trigger error.
In order to reduce the effect of-input signal noise the trigger-error can be reduced by
: raising the input voltage or by rectifying the input-wave into rectangular wave-form
applying to LDC-824(S).
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6.
MAINTENANCE
(1)
To calibrate or adjust the reference oscillator.
Set GATE TIME selector to 10s and FREQ. RANGE selector to 80 MHz.
A standard 10MHz signal generator with an accuracy greater than +1 X 107° is required for
calibration.
Apply
the
output
of
standard
signal
generator
to
the
input
terminal
of
LDC-824
(S) to measure the frequency. A normally operating counter displays 10MHz. If you read
other
than
1OMHz,
adjust
the
trimmer
capacitor
with
the
screw
driver
through
the
hole
for
adjustment
provided
at
the
rear
panel
of
the
LDC-824(S),
in
order
to
make
exact
accurate
display.
(2) The LDC-824(S) has been designed for easy maintenance and high reliability by employing
(3)
LSI/MSI IC’s for the digital and power-source sections of this instrument.
If the instrument fails to perform in the manner specified herein, write or call your nearest
Leader office for factory-trained service. For safety reasons, and to prevent damage to the
instrument, DO NOT REMOVE the unit from the case.

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