4.4.10 Filter
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The time constant (time it takes to settle to within 36.8% of the step value after a step
change) for a given number of filter points can be derived using the following formula:
TC = 0.1 / (ln (N / (N - 1)), where TC is one time constant, and N is the number of filter
points. A reading is usually considered settled after six time constants. TABLE 4-12
shows a sampling of filter settings and the resulting time constant, settle time, and
equivalent noise bandwidth.
The filter window is a limit for restarting the filter. If a single reading is different from
the filter value by more than the limit, the instrument will assume the change was
intentional and restart the filter. Filter window is set in percent of full scale range.
When the Model 3062 4-channel scanner option card is installed, the time it takes to
get a new reading is increased if more than one scanner channel is enabled
or
a
channel is configured for a range that requires a reduced update rate. This reduction
in update rate modifies the time constant of the filter. The time constant of the filter
can be derived using the formula TC = T/(In(N/(N-1)), where TC is one time constant, T
is the update rate of the channel in seconds per reading, and N is the number of filter
points. Refer to section 4.4.8.2 for information on update rates of the Model 3062.
TABLE 4-13 shows a sampling of enabled scanner channels with the number of filter
points set to 8 and resulting time constant, settle time, and equivalent noise band-
width.
Menu Navigation:
Input Setup
Q
Input
(A, B, C or D)
Q
Filter
Q
(Off or On)
Input Setu
p
Q
Input
(A, B, C or D)
Q
Filter Points
Q
(2 to 64)
Input Setup
Q
Input
(A, B, C or D)
Q
Filter Window
Q
(1% to 10%)
Default:
Filter
Q
(Off)
Filter Points
Q
8
Filter Window
Q
10%
Filter points
Time constant
Settle time
(6 time constants)
Equivalent noise
bandwidth (
p
TC)
2
0.14 s
0.9 s
1.733 Hz
4
0.35 s
2.1 s
0.719 Hz
8
0.75 s
4.5 s
0.334 Hz
16
1.55 s
9.3 s
0.161 Hz
32
3.15 s
18.9 s
0.079 Hz
64
6.35 s
38.1 s
0.039 Hz
TABLE 4-12
Filter settle time and bandwidth
Scanner channels
enabled
Time constant with 8
filter points
Settle time (6 time
constants)
Equivalent noise
bandwidth (
p
TC)
1
0.75 s
4.5 s
0.334 Hz
2
1.50 s
9 s
0.167 Hz
3
2.25 s
13.5 s
0.111 Hz
4
3.00 s
18.0 s
0.083 Hz
5
3.74 s
22.5 s
0.067 Hz
TABLE 4-13
Example of a filter settle time and bandwidth for a
Model 3062 4-channel scanner option card
Содержание 336
Страница 4: ...Model 336 Temperature Controller...
Страница 6: ...Model 336 Temperature Controller...
Страница 26: ...14 cHAPTER 1 Introduction Model 336 Temperature Controller...
Страница 54: ...42 cHAPTER 3 Installation Model 336 Temperature Controller...
Страница 84: ...72 cHAPTER 4 Operation Model 336 Temperature Controller...
Страница 104: ...92 cHAPTER 5 Advanced Operation Model 336 Temperature Controller...
Страница 164: ...152 cHAPTER 7 Options and Accessories Model 336 Temperature Controller...
Страница 178: ...166 cHAPTER 8 Service Model 336 Temperature Controller...