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8
PRECAUTIONS IN USING THE LT4H SERIES
Display
Contents
Malfunctioning CPU.
Enter reset input, RESET
key, or restart unit.
The values at start-up before the CPU
malfunction occurred.
0
Malfunctioning memory. See
note.
OFF
Output condition
Restoration procedure
Preset values after restoration
7. Self-diagnosis function
If a malfunction occurs, one of the following displays will appear.
Note: Includes the possibility that the EEPROM’s life has expired.
4) Regarding external noise, the values
below are considered the noise-resistant
voltages. If voltages rise above these
values, malfunctions or damage to the
internal circuitry may result, so take the
necessary precautions.
5) When connecting the operating power
supply, make sure that no leakage
current enters the timer. If you use a
contact protection circuit such as that
shown in Fig. A, leak current can flow
back through the CR circuit and cause
erroneous operation. For this reason,
use the circuit shown in Fig. B.
6) Long periods of continuous operation
in the time-up completed condition (one
month or more) will result in the
weakening of the internal electrical
components from the generated heat
and, therefore, should be avoided. If you
do plan to use the unit for such
continuous operation, use in conjunction
with a relay as shown in the circuit in the
diagram below.
• Surge wave form
[± (1.2
50) µs uni-polar full wave voltage]
100
90
50
30
0
0
1.2
Time (
µ
s)
50
Peak
Surge voltage (%)
Operating
power supply
C
R
Leakage current
Operating
power supply
T
T
(Fig. A)
C
R
(Fig. B)
Receive output
from contact
at relay R
Timer
Relay
R
R
T
R
T
R
Timer
As NPN output
Load’s power supply
Load’s power supply
Timer
As PNP output
Load
Load
4) The input signal is applied by the
shorting of each input terminal with the
common terminal. Never connect other
terminals or voltages higher than 40V
DC, because it may destroy the internal
circuitry.
5) Transistor output
(1) Since the transistor output is
insulated from the internal circuitry by
a photocoupler, it can be used as an
NPN output or PNP (equal value)
output.
6) When wiring, use shielded wires or
metallic wire tubes, and keep the wire
lengths as short as possible.
7) For the load of the controlled output,
make sure that it is lower than the rated
control capacity.
4. Operation of LT4H digital timer
1) Turning on and off the power supply
while operating in A2* (Power on delay
2) or G (Totalizing On delay) will result in
a timer error to be generated due to the
characteristics of the internal circuitry.
Therefore, use the start input or stop
input.
* Not related to the start input.
2) When controlling the timer by turning
on the power supply, use only A (Power
on delay 1) or A2 (Power on delay 2).
Use of other modes in this situation will
result in timer errors. When using the
other modes, control the timer with the
start input or stop input.
5. Operation mode and time range
setting
The operation mode and time range can
be set with the DIP switches on the side
of the timer. Make the DIP switch
settings before installing the timer on the
panel.
Noise wave form (noise simulator)
Rise time: 1 ns
Pulse width: 1 µs, 50 ns
Polarity: ±
Cycle: 100 cycles/second
6. Conditions of usage
1) Avoid locations subject to flammable
or corrosive gases, excessive dust, oil,
vibrations, or excessive shocks.
2) Since the cover of the timer is made of
polycarbonate resin, avoid contact with
or use in environments containing methyl
alcohol, benzene, thinners, and other
organic solvents; and ammonia, caustic
sodas, and other alkaline substances.
3) If power supply surges exceed the
values given below, the internal circuits
may become damaged. Be sure to use
surge absorbing element to prevent this
from happening.
Operating voltage Surge voltage (peak value)
AC type
6,000V
DC type
AC/DC type
1,000V
Power supply terminals
Input
terminals
AC type
DC type
AC/DC type
Noise
voltage
1,500V
1,000V
600V
LT4HL 02.1.9 6:25 PM Page 8