18-32 SCPI Command Reference 2400 Series SourceMeter
®
User’s Manual
arrays will be created. The calculation will now yield two results, one
for each array.
The first result, as before, is based on the fourth and 10th readings of the
first array. The second result is based on the 14th and 20th readings.
These are the fourth (vector 3) and 10th (vector 9) readings of the sec-
ond array.
Note that you need complete vector arrays to acquire valid calculation
results. If, in the preceding example, the SourceMeter is changed to per-
form 25 source-measure operations, then the third array will be incom-
plete (first array is 10 readings, second array is 10 readings, third array
is only 5 readings). After the SourceMeter goes back into idle, the
“Insufficient vector data” error message will be displayed, and the third
result will be NAN (+9.91e37).
To avoid incomplete vector arrays, make sure the programmed number
of source-measure operations (arm count × trigger count) is a multiple
of the vector array size. In the preceding example, vector array size is
10. Thus, in order to avoid “Insufficient vector data” errors, the pro-
grammed number of source-measure operations has to be a multiple of
10 (10, 20, 30, 40, and so on).
The following vector math expression to calculate offset compensated
ohms demonstrates proper syntax:
:calc:math ( (volt[1] - volt[0]) / (curr[1] - curr[0]) )
Notes:
1. Use nested parentheses to force math operations that are imbedded
in the calculation (see example in “Vectored math,” page 18-31).
2. A calculation expression can be up to 256 characters in length,
including parentheses and white spaces.
3. When using the filter, the measured readings used in the calculation
are filtered - NOT the result of the calculation.
4. For vector math, it is recommended that only the REPEAT filter be
used. For the repeat filter, the calculations use only the filtered read-
ings of the vector points. If you instead use the MOVING filter,
each vector point will reflect the filtered average of all the previous
readings in the vector array.
5. The data format (ASCII or binary) for calculation results is selected
using the :FORMat:DATA? command. (See “FORMat subsystem,”
page 18-49.) The *RST and :SYSTem:PRESet default is ASCII.
6. When brackets ([]) are left out of an expression, it is assumed that it
is referencing the first vector point in the array (i.e., VOLT is the
same as VOLT[0]).
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