Read Commands; Delta; Model 622X Measurement Process - Keithley 6220 DC User Manual

Model 6220/6221 User's Manual

Read commands

The Model 622x does not perform measurements. However, raw readings are
sent from the Model 2182/2182A to the Model 622x to calculate Delta, Pulse
Delta, or Differential Conductance readings. Readings from the Model 2182/
2182A are processed, stored, and displayed by the Model 622x.
The following read commands return pre-math readings and buffer readings.
Details on all read commands are provided in Section 5 of the Reference Manual.
Pre-math readings
SENSe[1]:DATA[:LATest]?
SENSe[1]:DATA:FRESh?
While Delta, Pulse Delta, or Differential Conductance is running, the
SENS:DATA:LATest? command can be sent to read the latest (last) pre-math
reading processed by the Model 622x. The returned reading will be filtered if the
averaging filter is enabled. If this read command is sent before a new reading is
available, the last reading will again be returned.
The SENS:DATA:FRESh? command is the same as the SENS:DATA:LATest?
command except that once a reading is returned, it cannot be returned again. This
read command guarantees that each reading gets returned only once. If a new
(fresh) reading is not available when SENS:DATA:FRESh? is sent, error -230
Data corrupt or stale will occur.
Buffer readings
TRACe:DATA?
This is the read command to return all readings stored in the buffer. There are
also commands to determine the type of readings stored in the buffer, specify a
list of consecutive buffer readings to return, and to read the selected buffer statis-
tic. See "Data flow and read commands" in Section 5 of the Reference Manual.

Delta

Model 622x measurement process

The Delta process is shown in
A/D conversions are performed to yield a single Delta reading. When Delta starts,
three Model 2182/2182A A/Ds (A, B, and C) are performed and the Delta reading
is calculated. After the first Delta cycle, the moving-average technique is then
used. As shown, a Delta reading is yielded for every subsequent
Model 2182/2182A A/D. The new A/D replaces the oldest A/D in the Delta
calculation.
Delta, Pulse Delta, and Differential Conductance 5-13
Figure 5-6. As shown, three Model 2182/2182A
Return to Section 5 topics