Controlling Devices Using Pull-Up Resistors - Keithley 7021 Instruction Manual

Digital I/O Configuration
Each output channel uses a fly-back diode for protection
when switching an inductive device, such as a solenoid coil.
This diode diverts the potentially damaging fly-back voltage
away from the driver.
CAUTION
Failure to set J201 to the V
when using external pull-up voltages
may result in damage to the output
drivers.
7021
5V
Figure 3-2
Output configuration using pull-up resistance
3-2
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position
ext
Jumper
V
EXT
R
P
10kΩ
Driver

Controlling devices using pull-up resistors

When interfacing outputs to high-impedance devices (i.e.
logic devices), internal pull-up resistors are used to achieve
the appropriate logic level. Figure 3-2 shows the output con-
figuration using the 10k Ω pull-up resistor (R
The configuration in Figure 3-2 uses the internal 5V source
as the high logic level. If you need a higher logic level, you
can place the jumper in the alternate position and apply an
external voltage (via V ).
EXT
+V
A
Or
B
gate
Logic
device
GND
).
P
Y