Model 6220/6221 Reference Manual Averaging Filter, Math, and Buffer 6-13
Return to Section 6 topics
• Mean is the mean average of the buffer readings. Mean is calculated as
follows:
Where: X
i
is a stored reading.
n is the number of stored readings.
•The STD DEV value is the standard deviation of the buffered readings.
Standard deviation is calculated as follows:
Where: X
i
is a stored reading.
n is the number of stored readings.
Avg is the mean of the buffer readings.
See "Recall," on page 6-14 for details on recalling buffer statistics.
Buffer timestamp
Each buffer reading has a timestamp. The absolute timestamp is referenced to the
first stored reading in the buffer, which is timestamped at 0.0s. For front panel
operation, the absolute timestamp is used for every buffer reading.
For remote programming, the timestamp can be set for absolute or delta. The
delta timestamp indicates the time between readings. Buffer commands are docu-
mented in Table 6-4. The following command demonstrates proper syntax to set
the timestamp.
Example – Select the delta timestamp:
NOTE If any readings stored in the buffer are the result of an
overflow or compliance condition, the buffer statistics
calculation will not be performed. Buffer recall via front
panel operation will show a series of dashes in place of
the requested buffer statistics value. For remote opera-
tion, the corresponding buffer statistics will be repre-
sented by the value +9.91e37.
TRACe:TSTamp:FORMat DELta ‘ Select the delta timestamp.
y
X
i
n
-----
i1=
n
∑
=
y
Avg X
i
–()
2
i1=
n
∑
n1–
---------------------------------------=
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