Keithley 7037, Инструкция по эксплуатации

Страница: 19 / 72

Digital I/O Configuration
3-2
Figure 3-2
Output configu ation using pull-up resistance
Controlling devices using pull-up resistors
CAUTION
Failure to set J201 to the Vext position
when using external pull-up voltages
may result in damage to the output
drivers.
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 configuration using the 10 Ω pull-up resistor (Rp).
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
).
Digital inputs
Input channels use positive true logic but can be pulled up or
pulled down based on the configuration of the pull-up resis-
tor. Each channel uses a 10k Ω pull-up resistor (R
1
). The pull-
up resistors can be pulled up to 5V or pulled down to ground
depending on the positioning of the jumper on the input
logic bank. Refer to Section 4 for more information. Figure
3-3 shows the resistor being pulled up to 5V.
When the resistor is connected to 5V, the channel is pulled
high. Thus, with nothing connected to the channel, the input
is pulled high to 5V which displays the channel as on.
When the resistor is connected to ground, the channel is
pulled low. Thus, with nothing connected to the channel, the
input is pulled low to ground which displays the channel as
off.
The digital input is compatible with external TTL logic.
Each built-in pull-up resistor provides level shifting so
devices such as micro-switches can be monitored. Each input
has a protection network that clamps the input at 5.7V. This
allows logic levels up to 42V peak to be monitored.
Figure 3-3
Input configu ation
Driver
Jumper
5V
V
EXT
Logic
Device
7037
R
P
10k
Ω
GND
Or
Gate
A
B
Y
+V
INPUT
7037
R
2
10k
Ω
GND
R
1
10k
Ω
R
1
= Pull-up resistor
R
2
= Input protection resistor
5V