64 Rockwell Automation Publication 1756-UM540E-EN-P - December 2017
Chapter 4 Temperature-sensing Analog Modules
1756-IR12 and 1756-IT16 Notch Filter Setting
The following tables lists the available Notch Filter settings for the 1756-IR12
and 1756-IT16 modules.
If your application requires a Notch Filter setting of 50 Hz, the module’s
minimum RPI rate is 80.4 ms. In this case, sampling speed is more important
than noise rejection. The module automatically uses a SINC^1 filter.
If your application requires a Notch Filter setting of 50 Hz and the greater level of
noise rejection provided by a SINC^3 filter, the minimum RPI rate is 240.4 ms.
The module automatically uses a SINC^3 filter.
The RPI must be > 4/Notch Filter plus some small scan time for the ADC to
sample properly. The SINC^3 filter takes three times as long and thus requires
RPI > 12/Notch plus some small scan time. The module rejects combinations
which violate that relationship.
To see where to set the Notch Filter, see page 132
.
Table 14 - 1756-IR12 and 1756-IT16 Notch Filter Settings
Notch Setting 20 Hz 50 Hz 60 Hz (Default) 100 Hz 500 Hz 1000 Hz 5000 Hz
Minimum Sample Time (RPI) -
SINC^1 Filter
(1)
200.4 ms 80.4 ms 67.1 ms 50.0 ms 50.0 ms 50.0 ms 50.0 ms
Minimum Sample Time (RPI) -
SINC^3 Filter
(1)
600.4 ms 240.4 ms 200.4 ms 120.4 ms 50.0 ms 50.0 ms 50.0 ms
0…100% Step Response Time
(2)(3)
600 ms + 1RPI 240 ms + 1RPI 200 ms + 1RPI 120 ms + 1RPI 6 ms + 1 RPI 3 ms + 1RPI 1 ms + 1RPI
-3 dB Frequency
(2)
5.1 Hz 13 Hz 15 Hz 26 Hz 128 Hz 258 Hz 1296 Hz
Typical Effective Resolution
(2)
(4)
18 bits 17 bits 17 bits 17 bits 16 bits 15 bits 14 bits
(1) The notch filter setting is set on a module basis.
(2) Using the SINC^3 filter.
(3) Worst case settling time to 100% of step change includes 0…100% step response time plus one RPI sample time.
(4) The 1756-IR12 setting is measured in 0…5000
Ω range. The 1756-IT16 setting is measured in ±100 mV range.
Notch Filter Fastest Available RPI Fastest RPI for a SINC^3 Filter
20 Hz 200.4 ms 600.4 ms
50 Hz 80.4 ms 240.4 ms
60 Hz (default) 67.1 ms 200.4 ms
100 Hz 50.0 ms 120.4 ms
500 Hz 50.0 ms 50.0 ms
1000 Hz 50.0 ms 50.0 ms
5000 Hz 50.0 ms 50.0 ms
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