Table of Contents
Advertisement
Chapter 10
Operate the Module
300
And while accuracy is important, minimizing the signal noise is equally so. The
1444 design addresses signal noise in many ways, such as:
• Signals are isolated from ground. This isolation makes sure that there are
consistent, accurate measurements regardless of the quality (or presence)
of the earth ground.
• Instrument ground does not connect to the DIN rail. This status
minimizes the effects that other instruments can cause on the same DIN,
perhaps with different ground potentials.
• Connecting the signal wiring directly to the module rather than routing
the signals through a noisy terminal base and an additional pin
connector (module to base).
Firmware design can also affect measurement accuracy. In most cases, verify
accuracy by following industry standards and by using proven solutions in
digital signal-processing function design. One aspect though is crucial to
accuracy - the quality of digital filters.
In most cases, the extraordinary filtering that is available in hardware is all that
is needed. When digital filtering is necessary it is essential to apply a filter that
minimizes signal attenuation on the passband side of the filter, and that
maximizes attenuation on the filter side. In the 1444 design, when a digital
filter must be used, you have three choices to apply.
The three choices are:
• -24 dB/octave filter, available on the primary signal path
• -60 dB/octave filter, available on the primary path if the measurement
type is Aeroderivative
• -48 dB/octave filter on the alternate signal processing path
Choose the best filter to apply based on the measurement requirements. This
choice allows you to affect or verify the greatest possible signal accuracy when
that is the most important requirement.
Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Hide quick links:
Advertisement
Table of Contents
