Keithley 2750 - Page 270

Model 2750 Multimeter/Switch System User’s Manual Limits and Digital I/O 9-9
Figure 9-4
Controlling externally powered relays
4.75k
Ω
Pull Up Resistor
Pin 9 - Digital Ground
Digital Output
Pin 7 - Diode Clamp
Relay
Coil
Relay
Coil
+
+
-
-
External Power
(+5V to +33V)
External Power
(+5V to +33V)
Model 2750
Transistor Switch
Flyback
Diode
Equivalent Circuit
Digital Output #1
Flyback Diode
Control
Line
33V
+5V
2750-900-01.book Page 9 Wednesday, August 3, 2011 7:56 AM