322
Chapter 7 Tutorial
Relay Life and Preventive Maintenance
Relay Life
As a relay is used, the contacts begin to wear and the resistance of the
closed contacts increases. The initial contact resistance of a relay is
typically 50 m
(plus lead resistance). When the contact resistance
exceeds 20 to 50 times its initial value, the contact resistance becomes
very erratic and the relay should probably be replaced. For most
applications, a relay with contact resistance greater than 1
should be
replaced. The graph below shows the typical contact resistance
characteristics of the relays used on the 34970A/34972A switching
modules.
Relay Load
For most applications, the load switched by the relay is the most
important factor affecting relay life. As shown in the graph below, relay
life is maximized by switching low power. As the power switched
increases, relay life deteriorates.
1k
10k
100k
1M
10M
100M
0
1
Typical Relay Lifetime
Relay Operations (Cycles)
Re
lay
Cont
ac
t R
esist
ance
Full Load
Typical Signals No Load
Maximum Switching Capacity
Vo
ltage
Switched
300V
240V
180V
120V
60V
0.2A
0.4A
0.6A
0.8A
1A
10 mA 20 mA 30 mA 40 mA 50 mA
Reed (34902A)
Armature (34901A, 34903A, 34904A, 34908A)
Current Switched
34970A Refresh UG.book Page 322 Wednesday, February 17, 2010 12:34 PM
Содержание 34970A
Страница 16: ...16 34970A Refresh UG book Page 16 Wednesday February 17 2010 12 34 PM ...
Страница 20: ...34970A Refresh UG book Page 20 Wednesday February 17 2010 12 34 PM ...
Страница 21: ...1 1 Quick Start 34970A Refresh UG book Page 21 Wednesday February 17 2010 12 34 PM ...
Страница 39: ...2 2 Front Panel Overview 34970A Refresh UG book Page 39 Wednesday February 17 2010 12 34 PM ...
Страница 59: ...3 3 System Overview 34970A Refresh UG book Page 59 Wednesday February 17 2010 12 34 PM ...
Страница 87: ...4 4 Features and Functions 34970A Refresh UG book Page 87 Wednesday February 17 2010 12 34 PM ...
Страница 217: ...5 5 Error Messages 34970A Refresh UG book Page 217 Wednesday February 17 2010 12 34 PM ...
Страница 240: ...240 Chapter 5 Error Messages Plug In Module Errors 34970A Refresh UG book Page 240 Wednesday February 17 2010 12 34 PM ...
Страница 241: ...6 6 Application Programs 34970A Refresh UG book Page 241 Wednesday February 17 2010 12 34 PM ...
Страница 254: ...254 34970A Refresh UG book Page 254 Wednesday February 17 2010 12 34 PM ...
Страница 255: ...7 7 Tutorial 34970A Refresh UG book Page 255 Wednesday February 17 2010 12 34 PM ...
Страница 324: ...324 34970A Refresh UG book Page 324 Wednesday February 17 2010 12 34 PM ...