Section 3: Functions and features
Model 2281S-20-6 DC Power Supply and Battery Simulator Reference Manual
3-26
077114601 / March 2019
Refer to the following figure for a simplified schematic of a sample control circuit for a relay. You can
externally power a different device by replacing the relay coil with the other device.
Figure 80: Digital I/O Vext (example external circuit)
When using the V
ext
pin to control externally powered devices, make sure to configure the
corresponding digital output lines. In the low state (0 V), the output transistor sinks current through
the external device. In the high state, the output transistor is off (transistor switch is open). This
interrupts current flow through the external device. Usually this type of application uses an active-low
(set the bit to 0) to turn the relay on (On = 0 V).
For example, if you configure line 4 as the digital output line, you can send the following commands to
sink relay current.
To sink relay current in the power supply function:
:DIG:LINE4:FUNC:MOUTL
To sink relay current in the battery test and battery simulator functions:
:BATT:DIG:LINE4:CONF MAN,MOUTL
To stop relay current in the power supply function:
:DIG:LINE4:FUNC:MOUTH
To stop relay current in the battery test and battery simulator functions:
:BATT:DIG:LINE4:CONF MAN,MOUTH
