Selecting Relays
A Mounting Structure and Type of Protection
-
-1 Type of Protection
If a Relay is selected that does not have the appropriate type of 
protection for the atmosphere and the mounting conditions, it may 
cause problems, such as contact failure. 
Refer to the type of protection classifications shown in the following 
table and select a Relay suitable to the atmosphere in which it is to 
be used.
Classification by Type of Protection
B-A-2 Combining Relays and Sockets
Use OMRON Relays in combination with specified OMRON Sockets. 
If the Relays are used with sockets from other manufacturers, it may 
cause problems, such as abnormal heating at the mating point due to 
differences in power capacity and mating properties.
B-A-3 Using Relays in Atmospheres Subject to Dust
If a Relay is used in an atmosphere subject to dust, dust will enter 
the Relay, become lodged between contacts, and cause the circuit to 
fail to close. Moreover, if conductive material such as wire clippings 
enter the Relay, it will cause contact failure and short-circuiting.
Implement measures to protect against dust as required by the 
application.
B Drive Circuits
B-B-1 Providing Power Continuously for Long Periods
If power is continuously provided to the coil for a long period, 
deterioration of coil insulation will be accelerated due to heating of 
the coil. Also see 3-2-7 Using with Infrequent Switching.
B-B-2 Operation Checks for Inspection and 
Maintenance
If a socket with an operation indicator is used, Relay status during 
operation can be shown by means of the indicator, thereby facilitating 
inspection and maintenance.
Note: The built-in indicator shows that power is being provided to the 
coil. The indicator is not based on contact operation.
C Loads
B-C-1 Contact Ratings
Contact ratings are generally shown for resistance loads and 
inductive loads.
B-C-2 Using Relays with a Microload
Check the failure rate in the performance tables for individual 
products. 
Item Features Representative model Atmosphere conditions
Mounting 
structure
Type of 
protection
Dust and dirt Corrosive 
gases
PCB-mounted 
Relay
Flux protection Structure that 
helps prevent 
flux from 
entering Relays 
during soldering
G7SA Some protection
(No large dust or 
dirt particles 
inside Relay.)
No protection
Unsealed Structure that 
protects against 
contact with 
foreign material 
by means of 
enclosure in a 
case (designed 
for manual 
soldering)
G7S
Type Description Examples of 
applicable models
Built-in indicator LED G7S
G7SA
http://www.ia.omron.com/
C-4
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