Remote Programming - Buffer; Buffer Commands - Keithley SourceMeter 2790 Reference Manual

6-8
Standard deviation
This mode displays the standard deviation of buffered readings. The following equation is
used to calculate standard deviation:
y =
where:
klqb
Remote programming — buffer
klqb
klqb

Buffer commands

klqb
The commands to perform buffer operations are listed in
mands follow the table.
klqb
2
⎛ ⎛ ⎞ ⎞
n n
⎜ ⎜ ⎟ ⎟
1
∑ ∑
2
-- -
X – X
⎜ ⎜ ⎟ ⎟
i i
n
⎝ ⎝ ⎠ ⎠
i = n 1 – i = 1
-------------------------------------------------------------- -
–
n 1
y is the standard deviation.
X is a stored reading.
i
n is the number of stored readings.
If the standard deviation calculation is being performed on a buffer that has
more than 1000 readings, the "CALCULATING" message will flash to indicate
that the Model 2790 is busy. While busy with the calculation, front panel keys
will not operate.
When readings are stored in the buffer by the TRACe command (or by front
panel data store operation), INIT and multi-sample READ? queries are locked
out. With readings in the buffer that were stored in that manner, you cannot use
the INIT or READ? command if sample count is >1 (error -225, out of memory).
The measurement event register can be read to check when the buffer becomes ,
, , or full. Status registers are covered in
When measurements are performed, the readings are fed to other enabled oper-
ations, including the Buffer. Appendix C explains data flow and the commands
used to read the buffer and buffer statistics.
Optional command words and most queries are not included in
unabridged tables for all SCPI commands are provided in
Model 2790 SourceMeter
Section
®
Switch System Reference manual
11.
Table 6-1. Details on these com-
Table
Section 15.
6-1. The