Keithley 7707, Руководство пользователя

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16
An output line can be set high to
≈
4.3V or low to 0V (digital ground). Output lines are set as follows:
• Logic ‘0’ sets output line low to 0V (digital ground).
• Logic ‘1’ sets output line high to
≈
4.3V.
NOTE
A digital I/O channel must first be configured as an output port before its output lines can be set
high or low. See
Setting digital outputs on page 22 , for details.
Sink or source
A digital output line (bit) can be used as a sink for an external source (up to 40V), or as a
≈4.3
V source for a low-current
device.
Sink mode
As a sink, current provided by an external source flows into the module when the output line is set low (logic ‘0’). Using an
output line as a sink provides control for high voltage (up to 40V) and/or high current (up to 100mA) devices, such as relays,
solenoids, and other loads.
Figure 11, Figure 12, and Figure 13 show how to use an output line as a sink.
CAUTION Do not apply more than +40V to the K1, K2, K3, and K4 pins of the module. For the
output lines, do not exceed the maximum sink current. The maximum sink current for
an output line is 100mA. Exceeding these limits may cause damage to the instrument
that is not covered by the warranty.
Figure 11
Typical digital output—sink mode (with K1 protection)
Output
Control
(Ch 11 Bit 0)
Model 7707
Ch 11 Bit 0
Ground
User Supplied Circuitry
–
K1
Flyback
Diode
Zener
Clamp
K1 Protection Circuit
40V
External Source
Vmax = 40v
Imax = 100mA
Channel 11 set as
output port.
Relay
Flyback
Diode
–
External Source
≤
40V
+
Equivalent Circuit
+
* Logic ‘1’
position shown.
Transistor
Switch*
Note: Setting output line low (logic ‘0’) closes
transistor switch to energize relay coil.