Specifications

Series CU
Auto Switch Precautions 1
Be sure to read before handling.
1. Confirm the specifications.
Read the specifications carefully and use the product appropri-
ately. The product may be damaged or malfunction if it is used
outside the range of specifications for load current, voltage,
temperature or impact.
2. Take precautions when multiple cylinders are
used close together.
When two or more auto switch cylinders are lined up in close
proximity to each other, magnetic field interference may cause
the switches to malfunction. Maintain a minimum cylinder
separation of 40mm. (When the allowable interval is specified
for each cylinder series, use the indicated value.)
3. Monitor the length of time that a switch is on
at an intermediate stroke position.
When an auto switch is placed at an intermediate position of
the stroke and a load is driven at the time the piston passes, the
auto switch will operate, but if the speed is too great the
operating time will be shortened and the load may not operate
properly. The maximum detectable piston speed is:
4. Keep wiring as short as possible.
<Reed switches>
As the length of the wiring to a load gets longer, the rush
current at switching on becomes greater, and this may shorten
the product’s life. (The switch will stay on all the time.)
Use a contact protection box when the wire length is 5m or
longer.
<Solid state switches>
Although wire length should not affect switch function, use a
wire that is 100m or shorter.
5. Monitor the internal voltage drop of the switch.
<Reed switches>
1) Switches with an indicator light (except D-A96, D-A96V)
• If auto switches are connected in series as shown below,
take note that there will be a large voltage drop because of
internal resistance in the light emitting diodes. (Refer to
internal voltage drop in the auto switch specifications.)
[The voltage drop will be “n” times larger when “n” auto
switches are connected.]
Even though an auto switch operates normally, the load
may not operate.
Design and Selection
Auto switch operating range (mm)
Load operating time (ms)
x 1000
V (mm/s) =
• Similarly, when operating below a specified voltage, it is
possible that the load may be ineffective even though the
auto switch function is normal. Therefore, the formula
below should be satisfied after confirming the minimum
operating voltage of the load.
2) If the internal resistance of a light emitting diode causes a
problem, select a switch without an indicator light (D-A90, D-
A90V).
<Solid state switches>
3) Generally, the internal voltage drop will be greater with a 2-
wire solid state auto switch than with a reed switch. Take the
same precautions as in 1) above.
Also, note that a 12VDC relay is not applicable.
6. Monitor leakage current.
<Solid state switches>
With a 2-wire solid state auto switch, current (leakage current)
flows to the load to operate the internal circuit even when in the
off state.
If the condition given in the below formula is not met, the switch
will not reset correctly (it stays on).
Use a 3-wire switch if this condition cannot be satisfied.
Moreover, leakage current flow to the load will be “n” times
larger when “n” auto switches are connected in parallel.
7. Do not use a load that generates surge voltage.
<Reed switches>
If driving a load that generates surge voltage, such as a relay,
use a switch with a built-in contact protection circuit or a contact
protection box.
<Solid state switches>
Although a zener diode for surge protection is connected at the
output side of a solid state auto switch, damage may still occur
if a surge is applied repeatedly. When directly driving a load
which generates surge, such as a relay or solenoid valve, use a
type of switch with a built-in surge absorbing element.
8. Cautions for use in an interlock circuit
When an auto switch is used for an interlock signal requiring
high reliability, devise a double interlock system to safeguard
against malfunctions by providing a mechanical protection
function, or by also using another switch (sensor) together with
the auto switch.
Also, perform periodic maintenance inspections and confirm
proper operation.
9. Ensure sufficient clearance for maintenance
activities.
When designing an application, be sure to allow sufficient
clearance for maintenance and inspections.
Load
Warning
Minimum operating
voltage of load
Supply voltage – >
Internal voltage
drop of switch
Current to operate load (off condition) > Leakage current
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