3
SWITCHES
AND
SENSORS
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SAS-10
Standard Reed Switches are SPST or SPDT. The
Diagrams Below Show the Typical Wiring.
Form A SPST - Single Pole / Single Throw
Normally Open Dry
RED
RED
RED
RED
Normally Closed Dry
RED
RED
RED
RED
Form C SPDT - Single Pole / Double Throw
SPDT Dry Condition
BLACK
RED
N.O.
N.C.
COM.
WHITE/RED
Each level switch varies in rating depending on the unit, see the chart below
for electrical ratings.
The reed switch is designed for reliability to millions of cycles. To ensure
long life and repeatability, see the contact protection information below.
Contact Protection
In order to take advantage of the long life, highly reliable characteristics of
a reed switch, it is essential to provide protection when switching inductive
loads.
When current is interrupted, the inductance of the load generates a
high frequency voltage, which appears across the switch contacts.
If the voltage is large enough, it can cause arcing. Arcing can cause
the contacts to weld to each other resulting in unreliable switching
performance. It is essential to protect the circuit by suppressing the
voltage to prevent arcing. This can easily be accomplished through the
use of a diode for DC circuits (Figure 1) and a resistor-capacitor network
for AC circuits (Figure 2).
NOTE: Above ratings are for resistive loads only
Switch Ratings Max - Resistive Loads
Contact Rating Volts Amps AC Amps DC
10 VA 0-50 .20 .13
120 .08 .05
240 .04 N/A
20 VA 0-50 .40 .30
120 .17 .13
240 .08 .06
50 VA 0-50 .50 .50
120 .41 .41
240 .20 .20
100 VA 120 .83 N/A
240 .41 N/A
+ -
Reed
Switch
Inductive
Load
Figure 1
D.C. Contact Protection
Figure 2
A.C. Contact Protection
1N4004
+ -
Reed
Switch
Inductive
Load
100 1/4 Watt .1 uf .600 Volt
Contacts
Magnet
N
S
Hermetically
Sealed Glass
Common
Magnet
N
S
Hermetically
Sealed Glass
Normally
Open Blade
Normally
Closed Blade
Electrical Data
