Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules - Manual (Page 55)

Rockwell Automation Publication 1756-UM533C-EN-P - February 2011 55
1756-IF8H HART Analog Input Module Chapter 4
Module Filter
The module filter attenuates the input signal beginning at the specified
frequency. This feature is applied on a module-wide basis, affecting all channels.
The module attenuates the selected frequency by approximately -3 dB or 0.707 of
the applied amplitude. An input signal with frequencies above the selected
frequency is attenuated more while frequencies below the selection receive
no attenuation.
In addition to frequency rejection, a by-product of the filter selection is the
minimum sample rate (RTS) that is available. For example, the 1000 Hz selection
does not attenuate any frequencies less than 1000 Hz, and provides for sampling
of all 16 channels within 18 ms. The 10 Hz selection attenuates all frequencies
above 10 Hz and provides only for sampling all 16 channels within 488 ms.
Use the following table to choose a module filter setting.
IMPORTANT 60 Hz is the default setting for the module filter. Do not use the 1000 Hz
module filter with HART instruments.
.707
60 Hz 0
Table 2 - Module Filter Selections with Associated Performance Data
Module Filter Setting (-3 dB) (1)
10 Hz 15 Hz 20 Hz 50 Hz 60 Hz 100 Hz 250 Hz 1000 Hz
Minimum Sample Time (ms) (RTS) 488 328 248 88 88 56 28 18
Effective Resolution (+/-10V range) 17 bits 17 bits 17 bits 16 bits 16 bits 15 bits 14 bits 12 bits
0.16 mV 0.16 mV 0.16 mV 0.31 mV 0.31 mV 0.62 mV 1.25 mV 5.0 mV
Effective Resolution (0…10V range) 16 bits 16 bits 16 bits 15 bits 15 bits 14 bits 13 bits 11 bits
0.16 mV 0.16 mV 0.16 mV 0.31 mV 0.31 mV 0.62 mV 1.25 mV 5.0 mV
Effective Resolution (0…5V, 0 …20 mA,
4…20 mA range) 15 bits 15 bits 15 bits 14 bits 14 bits 13 bits 12 bits 10 bits
0.16 mV
0.63
μA
0.16 mV
0.63
μA
0.16 mV
0.63
μA
0.31 mV
1.25
μA
0.31 mV
1.25
μA
0.62 mV
2.5
μA
1.25 mV
5.0
μA
5.0 mV
20.0
μA
-3 dB Frequency 7.80 Hz 11.70 Hz 15.60 Hz 39.30 Hz 39.30 Hz 65.54 Hz 163.9 Hz 659.7 Hz
50 Hz Rejection 95 dB 85 dB 38 dB 4 dB 4 dB 2 dB 0.5 dB 0.1 dB
60 Hz Rejection 97 dB 88 dB 65 dB 7 dB 7 dB 2.5 dB 0.6 dB 0.1 dB
(1) Worst case settling time to 100% of a step change is double the real time sample time.