Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
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Measurement Definition
Chapter 4
Table 21 - Filters
Parameter
Values
Comments
FMAX
The available FMAX selections are as follows:
If the Channel measurement type = Aeroderivative the Range is limited to
22…36. A divisor is allowed per channel for Individually Multiplexed
channels only.
Select the desired FMAX
1
to be processed from the analog-to-digital
converter (ADC) of the hardware for this channel pair
2
. Except when
using the 40 kHz personality
3
, the selected value is the maximum
frequency that is available in an FFT that is not further decimated by
applying a lower FMAX in the primary path, or by applying a lower
FMAX or synchronous sampling in the alternate path.
1. The value that is written to the configuration assembly is the
Sample Rate Divisor, not the FMAX. Values from 1…36 are allowed.
Not all 36 selections are provided in the FMAX menu.
2. The module provides two ADCs, one for channels 0 & 1, and one for
channels 2 & 3. Each ADC samples at 93,750 samples per second
(187,500 for 40 kHz personalities) and then divides that by a
configurable Sample Rate Divide (SRD) value, settable from 2…36.
This calculation results in the measured sample rate. The divided
stream then is what is read from the hardware and defines the
effective FMAX for the selected channel pair (both channels must
use the same SRD).
3. It is not possible to process an FFT at the full 40 kHz bandwidth.
When the 40 kHz personality is selected, the primary path FMAX
must be set at no greater than 2747 Hz.
Because the module applies the SRD in hardware, rather than firmware,
specify the lowest FMAX practical to minimize load on the processor,
which can improve performance for other tasks.
Sample Rate
Displays the sample rate from the ADC based on the selected FMAX.
The displayed value is the calculated value from:
93750
Sample Rate Divisor
Primary Path Processing
Mode
Asynchronous
This mode is the sampling mode for the Primary Signal Path. It is not
editable.
FFT FMAX (Primary)
Select the desired Maximum Frequency (FMAX) for the primary signal
path.
See the following Decimation Tables for available selections.
The primary signal path includes a decimation stage that further
divides the sample rate (in firmware) from the output of the ADC.
The value that is written to the configuration assembly is the
Primary Path Decimation, not the FMAX. Values from 1…255 are
possible. Not all selections are provided in the FMAX menu.
The available FMAX selections are dependent on, and vary based on,
the selected ADC Out FMAX.
Sample Rate (Primary)
Displays the sample rate of the data in the
Primary Signal Path.
The displayed value is the calculated value from:
93750
(SRD x Primary Path Decimation)
Enable Low Pass Filter
Check to enable the Primary Path Low Pass Filter (LPF)
When checked, an LPF corner frequency can be applied to the primary
signal path.
The LPF is available when:
• The primary path is not decimated (FMAX = ADC out FMAX)
• The measurement type is not dynamic pressure (unfiltered version)
FMAX
SRD
Conditions
41200* 1
Available for 40 kHz Module Personalities (Module
Definition), and if the Measurement Type (Hardware
Page) is one of “40 kHz absolute vibration (A to A)”, “40
kHz absolute vibration (A to V)” or “gSE”
*40 kHz measurements allow for ONLY an overall
measurement on the 40 kHz signal at the ADC out
signal source. FFTs that are read using this FMAX must
be from a subsequently reduced FMAX on the primary
path, with a maximum FMAX available of 2747 Hz.
20600
2
Available for the 20 kHz Module Personality (Module
Definition), and if the Measurement Type (Hardware
Page) is NOT any of the “40 kHz…”, or either of the
absolute vibration (A to A)”, “40 kHz absolute vibration
(A to V)” or “gSE”
13733
3
10300
4
8240
5
6866
6
5866
7
4578
9
Available for all 4 kHz and 20 kHz Module Personalities
(Module Definition), and if the Measurement Type
(Hardware Page) is NOT a “40 kHz…” type or either of
the aeroderivative types.
3433
12
2289
18
2060
20
1873
22
Available for all 4 kHz and 20 kHz Module Personalities
(Module Definition), and if the Measurement Type
(Hardware Page) is NOT a “40 kHz…” type.
1717
24
1585
26
1471
28
1373
30