Keithley 6487 Reference Manual

4-10 Range, Units, Digits, Rate, and Filters Model 6487 Reference Manual
Digital filter
Digital filter types
An additional filter parameter is type (type is either moving or repeating). Filter types are
compared in Figure 4-2.
Moving Filter — Every time a reading conversion occurs, the readings in the stack are
averaged to yield a single filtered reading. The stack type is first-in, first-out. After the
stack fills, the newest reading conversion replaces the oldest. Note that the instrument does
not wait for the stack to fill before releasing readings.
Repeating Filter — Takes a selected number of reading conversions, averages them, and
yields a reading. It then flushes its stack and starts over.
Figure 4-2
Digital filter types; moving and repeating
Conversion
#10
#9
#8
#7
#6
#5
#4
#3
#2
#1
Conversion
Reading
#10
Conversion
#12
#11
#10
#9
#8
#7
#6
#5
#4
#3
Conversion
Reading
#12
Conversion
#11
#10
#9
#8
#7
#6
#5
#4
#3
#2
Conversion
Reading
#11
A. Class - Average, Readings = 10, Type - Moving
Conversion
#10
#9
#8
#7
#6
#5
#4
#3
#2
#1
Conversion
Reading
#1
Conversion
#20
#19
#18
#17
#16
#15
#14
#13
#12
#11
Conversion
Reading
#2
Conversion
#30
#29
#28
#27
#26
#25
#24
#23
#22
#21
Conversion
Reading
#3
B. Class - Average, Readings = 10, Type - Repeating

Keithley 6487 Specifications

General

Type	Picoammeter/Voltage Source
Current Measurement Range	20 fA to 20 mA
Interfaces	GPIB, RS-232
Voltage Burden	< 200 µV
Input Impedance	>10^14 Ω
Power	100 V / 120 V / 220 V / 240 V
Basic Current Measurement Accuracy	0.4%