Keithley 2750, Руководство пользователя

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6-8 Buffer Model 2750 Multimeter/Switch System User’s Manual
Standard deviation
This mode displays the standard deviation of buffered readings. The following equation is
used to calculate standard deviation:
where: y is the standard deviation.
X
i
is a stored reading.
n is the number of stored readings.
NOTE
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 2750 is busy. While busy with the calculation, front panel keys
will not operate.
Remote programming — buffer
NOTE
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 G ,
H , I , or full. Status registers are covered in Section 11 .
Buffer commands
NOTE When measurements are performed, the readings are fed to other enabled oper-
ations, including the Buffer.
Appendix D explains “ Data flow (remote opera-
tion) ” and the commands used to read the buffer and buffer statistics.
The commands to perform buffer operations are listed in Table 6-1 . Details on these com-
mands follow the table.
y
X
i
2
i n 1 – =
n
∑
1
n
---
X
i
i 1 =
n
∑
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎛ ⎞
2
⎝ ⎠
⎜ ⎟
⎜ ⎟
⎛ ⎞
–
n 1 –
--------------------------------------------------------------- =
2750-900-01.book Page 8 Wednesday, August 3, 2011 7:56 AM