20 Configuration and Calibration Guide HD0679 Rev 1.2.0
is stable, for example, when measuring at the output from a silo, the averaging should be set
to ‘Raw’.
5 Filtering
Default filtering settings can be found in the relevant sensor default settings
engineering note, see Appendix A Document Cross Reference for details.
The Raw Unscaled reading is measured 25 times per second and may contain a high level of
‘noise’ due to irregularities in the signal as the material flows. As a result, this signal requires a
certain amount of filtering to make it usable for moisture control.
The default filtering settings are suitable for most applications, however they can be customised
if required to suit the application.
It is not possible to have default filtering settings that are ideally suited to all applications because
each will have different characteristics. The ideal filter is one that provides a smooth output with a
rapid response.
The Raw Moisture % and Raw Unscaled settings should
not
be used for control purposes.
The Raw Unscaled reading is processed by the filters in the following order; first the Slew Rate
Filters limit any step changes in the signal, then the Digital Signal Processing Filters remove any
high frequency noise from the signal and finally the smoothing filter (set using the Filtering Time
function) smoothes the whole frequency range.
Each filter is described in detail below.
5.1
Slew Rate Filters
The Slew Rate Filters are useful for clipping large peaks or troughs in the sensor reading
caused by mechanical interference in a process.
The filters set rate limits for large positive and negative changes in the raw signal. It is
possible to set limits for positive and negative changes separately. Options are: None, Light,
Medium and Heavy. The heavier the settings the more the signal will be ‘clipped’ and the
slower the signal response.
5.2
Digital Signal Processing
The Digital Signal Processing Filters (DSP) remove excessive noise from the signal using an
advanced algorithm. The filter reduces high frequency noise. The advantage of this filter is
that the DSP filter will treat all signals within a meaningful frequency range as valid. The result
is a smooth signal that responds rapidly to changes in moisture.
DSP filters are particularly useful in high noise applications such as a mixing environment.
They are less appropriate for low noise environments.
Options are: None, Very Light, Light, Medium, Heavy and Very Heavy.
5.3
Filtering Time (Smoothing Time)
The Filtering Time smoothes the signal after it has first passed through the Slew Rate filters
and then the DSP filters. This filter smoothes the whole signal and will therefore slow the
signal response. The Filtering Time is defined in seconds
Options are: 0, 1, 2.5, 5, 7.5, 10 and a custom time of up to 100 seconds.
Summary of Contents for Hydro-Mix
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Page 14: ...Chapter 1 Introduction 14 Configuration and Calibration Guide HD0679 Rev 1 2 0 ...
Page 28: ...Chapter 2 Configuration 28 Configuration and Calibration Guide HD0679 Rev 1 2 0 ...
Page 42: ...Chapter 4 Best Practices 42 Configuration and Calibration Guide HD0679 Rev 1 2 0 ...
Page 48: ...Chapter 5 Sensor Diagnostics 48 Configuration and Calibration Guide HD0679 Rev 1 2 0 ...
Page 52: ...Appendix A Document Cross Reference 52 Configuration and Calibration Guide HD0679 Rev 1 2 0 ...
