Hardy HI 1756-nDF - Manual (Page 21)

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Chapter 4
Weight
Filter Delay (ms) Quality Comment
0 0 Poor, no filtering
1 100 Fair, narrow filter window
2 270 – 2000 Excellent, Waversaver® filter selection
Note: ADC delay in not included in delay calculation as this delay is
consistent regardless of filter mode selected.
In addition a second filtering stage can be enabled which averages the current and
preceding ADC samples. This is a simple method to remove harmonics from the data
stream without introducing delay into the data path. For example, if NumAverages
parameter is set to 10 (default) and the weight update rate is 100Hz, a frequency notch
will occur every 10Hz in the sampled spectrum. This simple but effective filter is ideal
for removing harmonics at known frequencies within the sampled spectrum.
To calculate the preact value to compensate for in flight material, it is necessary to set
tolerances so that the weight processing algorithm can detect when amount of inflight
material falls within a user specified tolerance over a set number of samples. The
required parameters are shown in the following table. This processing does not add delay
into the signal processing path.
Parameter Default Description
steady period 128 Sets the number of samples used to calculate the steady
weight value used in the auto-preact function.
variation *1 Sets the peak to peak variation in weight values which will
be processed
capture *2 Sets the peak to peak variation in processed weight values
that will be used to calculate the weight value on the scale
after in flight material has settled.
*1: Default value set to 1/2,500 of maximum capacity of the load cell.
*2: Default value set to 1/10,000 of maximum capacity of the load cell
Overview of Flow Rate Control
The default setting for the flow rate will be kilograms per second (kg/sec); however the
time interval will be programmable to also include kilograms per minute (kg/min) and
kilograms per hour (kg/hr) and the weight value can be programmed to be in pounds
enabling lbs/sec, lbs/min, and lbs/hr flow rate to be generated.
The flow rate calculation is a filtering operation tailored to provide an accurate
measurement of the material flow rate over the specified period of time. As the update
period is typically faster than the flow rate unit of time, the HI-1756 nDF will scale the
current calculation to match the programmed flow rate unit of time, albeit hours, minutes,
or seconds.
The time base value sets the number of samples that will be reviewed each time a flow
rate calculation is made.