Spectrum Controls 1746sc-INI4vi User Manual
Page 27
Chapter 3: Things To Consider Before Using Your Module
23
Table 9. Channel update time
(based on number of channels enabled and filter frequency)
Filter Frequency
# of ch. enabled 50 Hz
60 Hz
250 Hz
500 Hz
Current Input
1
20.0 ms
16.6 ms
4.0 ms
4.1 ms
2
20.5
17.7
7.3
7.3
3
19.8
16.6
10.6
10.7
4
21.0
17.0
13.8
13.8
Voltage Input (-INI4vi only)
1
19.7 ms
16.6 ms
5.0 ms
5.0 ms
2
19.7
17.2
9.2
9.2
3
19.7
16.6
13.5
13.5
4
19.7
18.0
18.0
18.0
The 3 dB cut-off frequency is the frequency at which input signals are
passed with 3 dB of attenuation.
Choose a filter frequency so that the frequency of your fastest changing
signal is lower than that filter’s 3 dB cut-off frequency. All frequency
components above the 3 dB cut-off frequency are increasingly
attenuated, as shown in the following figures.
Figure 6. Signal attenuation with 50 Hz input filter
0
-20
-40
-60
-80
-100
-120
-140
-160
-180
-200
0
50
100
150
200
250
300 Hz
-3 dB
13.1 Hz
Amplitude (in dB)
Signal Frequency