Measurement Definition - Allen-Bradley 1444-TSCX02-02RB User Manual

Chapter 4

Measurement Definition

Table 21 - Filters (continued)
Parameter Values
Low Pass Filter Enter a corner frequency between 10 Hz and the Max Cut off Frequency
(default).
High Pass Filter 0.1...1000 Hz
(Primary) Frequency
Alternate Processing Processing Mode
Path Processing Mode • OFF
• Synchronous
• Asynchronous
FFT FMAX (Alternate) Select the desired Maximum Frequency (FMAX) for the alternate signal
path.
See the following Decimation Tables for available selections.
Sample Rate (Alternate) Displays the sample rate of the data in the Primary Signal Path.
Fmax (Alternate) Tacho 0, 1
Source
Fmax (Alternate) Select from:
Samples Per Revolution • 8
• 16
• 32
• 64
• 128
126 Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Comments
Enter the frequency where the filter has attenuated the signal by 3 dB.
Frequencies higher than 3 dB are attenuated -24 dB/octave (-60 dB/
octave if the channel measurement type is aeroderivative).
Enter the frequency where the filter has attenuated the signal by 3 dB.
Any frequency lower than this frequency is attenuated -24 dB/octave (-
60 dB/octave if the channel measurement type is aeroderivative).
• The HPF is not available when the channel measurement type is set
to X (shaft relative), Y (shaft relative), or dynamic pressure
(unfiltered).
• For channel measurement types that specify integration, it is
performed at the outlet of the high pass filter.
• If a signal includes a DC offset, it is only removed (AC coupled) within
the high pass filter. If no HPF is applied, the signal includes any DC
offset *DC coupled).
Select the sampling mode to apply to the alternate signal path data.
• Alternate Path is available when the ADC out FMAX is less than or
equal to 4578 Hz.
• Synchronous measurement modes are available only when a
physical speed signal is available (see
from any of Tacho Bus 0/1 or Local TTL Tach Input 0/1.
When asynchronously sampling, the alternate signal path provides a
decimation stage that further divides the sample rate (in firmware)
from the output of the ADC. This selection presents selected FMAX
values that are based on the Module Personality (Module Definition)
and the sample rate out of the ADC.
The value that is written to the configuration assembly is the
Alternate Path Decimation, not the FMAX. Values from 1...255 are
possible. Not all selections are provided in the FMAX menu.
The displayed value is the calculated value from:
93750
(SRD x Alternate Path Decimation)
Select the speed source for the tacho input to be used in the
synchronous measurement.
• Tacho Source is applicable only to synchronous measurement
Processing Modes.
• Available Tacho Sources are only those sources that are defined from
a Tacho Bus or a TTL Input (see Speed
• Synchronous measurements require a 1/rev signal. If the Pulses Per
Revolution attribute is set, the TSC module outputs a 1/rev TTL to
the Tacho Bus. You must help verify that a Local TTL Input source is a
1/rev signal.
Select the number of samples to be measured per shaft revolution.
• Samples per Revolution is applicable only to synchronous
measurement Processing Modes.
• As Samples Per Revolution is increased:
– The synchronous sample rate increases, the measurement (FFT)
bandwidth increases, and there are more orders available for
analysis.
– A particular FFT has lower resolution (lines per order) or
bandwidth/number of lines.
– The maximum machine rpm that can be measured reduces
(sampling frequency = rpm x samples per rev).
Speed Page). Source can be
Page).