Keithley 6487 Reference Manual page 137

Model 6487 Reference Manual
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An externally powered relay connected to the digital output port is shown in
Other externally powered devices can be similarly connected by replacing the relay with
the device. When the output line is set LO (0V), the output transistor sinks current through
the external device. In the HI state, the output transistor is off (transistor switch open).
This interrupts current flow through the external device.
Figure 8-10
Controlling externally powered relays
To three other
digital outputs
Digital Output #1
Flyback Diode
Do not exceed +33V maximum voltage on pin 5 of the digital I/O port
and do not use any output line to sink >500mA. Exceeding these limits
may cause damage to the instrument that is not covered by the
warranty.
Model 6487
+5V
1kΩ
Pull Up
Resistor
Flyback
Diode
Limit Tests and Digital I/O
Pin 5 - External Voltage Flyback Connection
Relay
Coil
Pin 1 - Digital Output #1
Pin 9 - Digital Ground
Equivalent Circuit
(+)
Relay
Coil
(-)
Figure 8-10.
(+)
External Power
(+5V to +33V)
(-)
External Power
(+5V to +33V)
Transistor
Switch
8-13