Keithley 6487 Reference Manual

Model 6487 Reference Manual SCPI Signal Oriented Measurement Commands 12-3
Programming example — The following command sequence selects and configures the
Model 6487 for “one-shot” measurements. Each subsequent READ? triggers a single
measurement and requests the reading.
CONF:CURR ' Perform CONFigure operations.
READ? ' Trigger measurement and request reading.
B) FETCh? Request latest reading
This command requests the latest post-processed readings. After sending this command
and addressing the Model 6487 to talk, the readings are sent to the computer. This com-
mand does not affect the instrument setup.
This command does not trigger a measurement. The command simply requests the last
group of readings. Note that this command can repeatedly return the same readings. Until
there is a new reading(s), this command continues to return the old reading(s). If your
application requires a “fresh” reading, use the :READ? command.
This command is automatically asserted when the :READ? or :MEASure? command is
sent.
C) READ? Trigger measurement(s) and request reading(s)
This command is used to trigger and acquire readings. The number of readings depends on
how the trigger model is configured. For example, if configured for 20 measurements (arm
count 1, trigger count 20), 20 sets of readings will be acquired.
When this command is sent, the following commands execute in the order they are
presented:
• INITiate
• FETCh?
If the instrument is in the idle state, INITiate takes the instrument out of idle to perform
the programmed number of measurements. If the instrument is not in the idle state, execu-
tion of this command will wait until it goes back into idle.
The FETCh? command is executed to acquire the reading(s). The readings are sent to the
computer when the Model 6487 is addressed to talk.
klqb If the instrument is programmed to perform an infinite number of measurements
(arm count or trigger count set to infinite), you cannot use the READ? command
to trigger and acquire readings. Use INITiate to start (trigger) the measurement
process, send ABORt to abort the measurement process, and then use
SENSe:DATA[:LATest]? to return the last (latest) reading.

Keithley 6487 Specifications

General

Type	Picoammeter/Voltage Source
Current Measurement Range	20 fA to 20 mA
Interfaces	GPIB, RS-232
Voltage Burden	< 200 µV
Input Impedance	>10^14 Ω
Power	100 V / 120 V / 220 V / 240 V
Basic Current Measurement Accuracy	0.4%