Figure 9-2 Sink Operation; Start-Of-Test (Sot) Line - Keithley 2520 User Manual

Model 2520 User's Manual

Start-of-test (SOT) line

The input line (SOT) is a TTL-compatible logic line used by external equipment to start a
test. With the ↓STEST trigger event selected, a low SOT pulse starts the testing process.
With the ↑STEST trigger event selected, a high SOT pulse starts the testing process. With
the ↑↓STEST trigger event selected, a high or low SOT pulse starts the testing process.
See Section 8 for triggering information,
NOTE
+5V output
The Digital I/O Port provides a +5V output that can be used to drive external logic cir-
cuitry. Maximum current output for this line is 300mA. This line is protected by a self-
resetting fuse.
Digital output configuration
There are two basic methods to connect external components to the digital output lines,
sink operation and source operation.
Sink operation
Figure 9-2
relay coil is connected between the digital output line (pins 1 to 4) and +5V (pin 7). With
this configuration, the digital output line must be set LO to energize the relay, and the
maximum sink current is 500mA.
Figure 9-2
Sink operation
Model 2520
+5V
Digital I/O Port, Interlocks, and Pulse Sync Output
SOT input pulses are referenced to ground (pin 9).
shows the basic output configuration for sink operation. Note that the external
Pin 7
Pins 1-4
Pin 9
Digital I/O
Port
External
Relay
Maximum Sink Current: 500mA
9-3
To Other
Circuits