Keithley 2002 User Manual

Front Panel Operation
2-71
The equation used to calculate the mean is:
where: x
i
is a stored reading, and
n is the number of stored readings.
Note: If n = 0, the result is NAN (not a number).
4. SDEV  This operation displays the standard deviation
of the stored readings, for example:
SDEV=1.4944e-03
The equation used to calculate the standard deviation is:
where: x
i
is a stored reading, and
n is the number of stored readings.
Note: If n ≤ 1, the result is NAN (not a number).
NOTE
These statistics are invalid if the measure-
ment function changed during data store
(e.g., when scanning different functions).
The Model 2002 uses IEEE-754 floating
point format for math calculations.
The last display in this series allows you to dump the buff-
ered readings to a printer. See paragraph 2.12.2 for details on
configuring printers.
2.9 Filter
Filtering stabilizes noisy measurements. The Model 2002
uses a digital filter, which is based on reading conversions.
The displayed, stored, or transmitted reading is simply an av-
erage of a number of reading conversions.
When a filter is enabled, the selected filter configuration for
that measurement function is in effect. Filtering is enabled
by pressing the FILTER key (FILT annunciator turns on).
Pressing FILTER a second time disables the filter.
Filtering is performed only on primary display measure-
ments; it has no effect on multiple displays.
2.9.1 Filter types
The Model 2002 has two types of digital filters: averaging
and advanced. Both types are a simple average of one to 100
reading conversions. The difference between them is the
user-programmable noise “window” of the advanced filter.
The noise window, which is expressed as a percentage of
range (0-100%), allows a faster response time to large signal
step changes (e.g., scanned readings). A reading conversion
outside the plus or minus noise window fills the filter “stack”
immediately.
If the noise does not exceed the selected percentage of range,
the reading is based on an average of reading conversions. In
this case, the advanced filter works the same as the averaging
filter. If the noise does exceed the selected percentage, the
reading is a single reading conversion, and new averaging
starts from this point. The two filter types are compared in
Figure 2-30.
2.9.2 Filter modes
An additional filter parameter is the mode, either moving or
repeating. A moving filter is a first-in, first-out stack, where
the newest reading conversion replaces the oldest. An aver-
age of the stacked reading conversions yields a reading.
Therefore, after a selected number of conversions, a moving
filter gives a new reading for every new conversion.
A repeating filter takes a selected number of reading conver-
sions, averages them, and yields a reading. It then flushes its
stack and starts over. This characteristic is useful when scan-
ning channels.
If burst mode is enabled with filtering, the post-processing
time increases. A filter mode setting of repeating is ignored
in burst mode.
Filter modes are compared in Figure 2-31.
y
X
i
i1=
n
∑
n
---------------=
X
i
2
-
1
n
---
X
i
i=1
n
∑






2



i=1
n
∑
n-1
-----------------------------------------------
y =

Keithley 2002 Specifications

General

Resolution	8.5 digits
DC Voltage Accuracy	±0.0006%
Maximum DC Voltage	1000 V
Maximum AC Voltage	750 V
Maximum DC Current	3 A
Maximum AC Current	3 A
Connectivity	GPIB, RS-232
DC Voltage Range	100 mV to 1000 V
AC Voltage Range	100 mV to 750 V
Resistance Range	10 Ω to 1 GΩ
Model	2002
Category	Multimeter
Interface	GPIB, RS-232
AC Current Accuracy	±0.1%
Frequency Range	0.1Hz to 300kHz
Display	VFD
Type	Digital
Power Supply	100-240V AC, 50/60Hz
Current Range (DC)	100 μA to 3 A
Current Accuracy (DC)	±0.01%
Current Range (AC)	100 μA to 3 A
Current Accuracy (AC)	±0.1%
DC Current Range	100 μA to 3 A
AC Current Range	100 μA to 3 A