Table Of Contents

Reducing Signal Noise

Last Modified: June 26, 2019

Configure hardware and software filters in FlexLogger to reduce noise in your signals.

FlexLogger supports both hardware and software filters for use in your project. Hardware filters offer a variety of filter type options to provide anti-aliasing and noise reduction with no CPU usage or reduction in system performance but are only available on specific modules. Software filters can be used on all input channels of any hardware supported by FlexLogger, but require high CPU resource usage and also have higher latency.

Using a Hardware Filter

FlexLogger applies the following hardware filters on supported devices. Refer to the Supported Hardware topic for information. Filter types vary depending on the module being used.

  1. Hover over the channel row to see the Configure gear . Click the gear for the channel you wish to configure the filter for.
  2. From the Channel Configuration dialog, click the Filtering tab and select from the following filter types.
    Table 1. Lowpass Filters
    Filter Type Description Comments
    Brickwall Best anti-aliasing Filter is automatically configured to a cutoff frequency of half the sample rate.
    Butterworth Better noise rejection, configurable filter order (2nd or 4th order) Flexlogger selects the default cutoff frequency based on the timing configuration and selected cutoff band; changes made to the cutoff settings are applied to all module channels and may affect other timing configurations on the module.
    Table 2. ADC Timing Mode-Based Filters
    Filter Type Description
    None (High Speed) Best sample rate and signal bandwidth, lower accuracy and noise rejection; this is the default filter applied to the channel.
    High Resolution Best accuracy and noise rejection, rejects power line frequencies, higher conversion time and lower signal bandwidth.
    Medium Resolution Better accuracy and noise rejection, rejects power line frequencies, higher conversion time and lower signal bandwidth.
    Medium Speed Better sample rate and signal bandwidth, lower accuracy and noise rejection.
    Best 50 Hz Rejection Optimizes 50 Hz noise rejection.
    Best 60 Hz Rejection Optimizes 60 Hz noise rejection.

The filter is applied when the Filter Type is selected, or if the filter configuration is set or changed (if configuration options are available for the selected filter).

Using a Software Filter

Refer to the Configuring Lowpass/Highpass Filter Channels topic for information on creating and configuring a software-based Butterworth filter channel.


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