Hardy HI 1756-nDF - Manual (Page 28)

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Chapter 4
cycle to when the relay changes state, and the capture time is the time from when the
relay changes state to when a weight value is taken (assumed to be available) to update
the auto_preact function. The following status values help to ensure the system timing is
configured correctly. A full picture of the cycle can be calculated by externally
monitoring the time from the start of the fill cycle to when the cycle ends.
Flow Rate Status
The flow rate compensation portion of the algorithm requires a constant, stable, flow rate
to be able to calculate the required value to compensate for in-flight material after the
relay changes state. If the not stable status value is a one, then the flow rate never became
stable before the relay changed state. This could be caused by one of the following
reasons:
1. The stable tolerance is too tight and the material is unable to meet the specified
percentage variation during the fill cycle.
2. The start wait value is too long and the period left to calculate a stable flow is
too short. This can be verified by reading the stable time and slow setpoint time
values. If the stable time is shorter than the start wait period, and is also less than
the setpoint time then the start wait time needs to be adjusted to provide at least
2 timebase periods between the measured stable time and slow setpoint time
values. If the slow setpoint time is less than the stable time then either the stable
tolerance or the material flow rate needs to be adjusted.
3. The flow rate for numerous reasons was changing throughout the fill cycle. This
may be by design and once identified the user can set the frc tolerance parameter
to zero, to disable this portion of the algorithm.
If the not stable status value is a zero, then the slow setpoint time provides a time
reference for stable time value, if the stable time value is multiple timebase periods long,
then adjustments to the flow rate could be considered to increase throughput.
Auto_preact Status
The programmed capture time value represents the time from when the relay state is
changed to when a weight value on the scale can be taken and used to adjust the
auto_preact function.
If the AP_NOT_STEADY status is a one, then the weight did not remain within the
capture tolerance on the scale for the specified steady period before the update time,
programmed time from relay changing state, was reached. To determine possible causes,
the programmed update time should be compared to the steady time status value which
represents the time from when the relay changes state to the first time the weight on the
scale remains within the capture tolerance for the programmed steady period. If the
update time is less than the steady time status duration, then either the update time needs
to be increased so that it exceeds the steady time status duration by at least 0.3 seconds to
allow a stable weight value to be calculated; or the update time needs to be increased so a
reliable weight value is available sooner. While the not steady status is a one, the
auto_preact value is not being updated. When adjusting the update time the auto_preact
values should be reset.
If the update time is greater than the steady time and the not steady value is zero, then the
system will stabilize and the correct auto_preact value will be generated to optimize the
process.