High Voltage SourceMeter Instrument Reference Manual Section 8:
2470-901-01 Rev. A / May 2019 8-15
Vext line
The digital I/O port provides a line (V
ext
) with a flyback diode clamp that you can use when controlling
inductive circuitry such as relay coils or low-power solenoids. You can use the built-in 5 V supply or
an external voltage supply for these types of applications. The externally supplied voltage can be up
to +33 V.
Do not apply more than 50 mA (maximum current) or exceed +33 V (maximum voltage) on the
digital I/O lines. Applying current or voltage exceeding these limits may damage the
instrument.
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. The relay is
actuated by configuring the corresponding digital output line. Most of these types of applications use
an active-low (set the bit to 0) to turn the relay on (ON = 0 V). 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.
Figure 128: Digital I/O Vext (example external circuit)
To Next Page
Loading...
Need help?
General
