Check Weigh Parameters

• variation_thd The check weigher computes filters with time constants of 64, 32, 16, and 2 samples. If the difference between the maximum and minimum samples over the time constant of a filter is greater than this parameter, the filter value is set to the value of the filter with a smaller time constant. This allows the filter to settle faster when a weigh jump occurs.
• Suggested value for the variation_thd is the scale capacity / 2500.0
• motion_thd The weight is set to the value the filter above with the largest time constant, provided that the difference between the max and min filter outputs over the time constant of the filter is less than this parameter.
• Suggested value for the motion_thd is the scale capacity / 10000.0
• check_period the rate at which a digital weigh scale card produces output samples.
• filter_sel is the level of filtering done by a digital weigh scale interface card.
• Status information for the check weigher can be read in the Check Status Word HSI16. Individual fields within this word are defined below.
• ON Check is the stable weight value measured on the scale. This value is held for the "check_hold" period after the weight is removed, and can be read in the mapping value HFI7. The Check Status Word bit 13 (HI16.13) indicates that this value is being updated. The check weigher updates this value if the weight is stable and above high_thd.
• OFF Check is the stable low weight value measured. This value can be read in the mapping value HFI8. The Check Status Word bit 14 (HI16.14) indicates that this value is being updated. The check weigher updates this value if the weight is stable and below low_thd.
• The status bit HI16.4 is set if the weight is below the low_thd. HI16.5 is set if the weight has transitioned from below the low_thd to some value between the low_thd and high_thd. HI16.6 is set if the weight is above the high_thd. HI16.7 is set if the weight has transitioned from above the high_thd to some value above the low_thd.
• If the OFF Check Weight is greater then twice the tamper threshold for 32 of the last 128 check cycles, the status bit HI16.11 is set.
• Check Weight - Check Weight is the ON weight minus the OFF weight minus the check_offset. check_offset is a user entered parameter, representing the weight of a package. The Check Weight can be read in the mapping value HFI9.
• check_hi, check_lo define the range where a Check Weight is considered OK. The Check Status Word bit 1 (HI16.1) indicates that the Check Weight is good. Check Status Word bits 0 and 2 (HI16.0, HI16.2) indicate under weight (HI16.0) and over weight (HI16.2). All 3 of these status bits are cleared when the Weight OFF is updated.
• Bit 3 (HI16.3) is set if the Check Weight is greater than the check_override parameter.
• Bits 4,5,6,7 of the check status words are progress indicators. Bit 4 is set if the weight is below the low_thd. Bit 5 is set if the weight is above the low_thd but has not yet gone above the high_thd. Bit 6 is set if the weight is above the high_thd. Bit 7 is set if the weight has dropped below the high_thd but has not yet gone below the low_thd.
• Bits 8,9,10 of the Check Status Word (HSI16) are quality indicators for the weight diff. 000 = none, 001 = bad, 010 = low, 011 = med low, 100 = med high, 101 = high, 110 = excellent. These bits are only set if there is stable weight on the scale, else they are cleared to 000.
• The check_hold is the number of seconds that the weight difference will continue to be available after the weight is removed
• The ON and OFF check weights are measured with respect to the check_zero weight. This gross weight value can be entered, or measured when there is no product on the scale. If the check low weight is more than twice the motion_thd, the error flag HI16.11 is set. The bit HI16.12 is set when a measurement of check low weight is in progress. This measurement takes about 2 seconds.
• The parameter check_lo_lo may be set to a value less than the check_lo, and the check_hi_hi parameter may be set to a value greater than the check_hi. This allows you to set ranges for marginally acceptable product weights. Bits in the second check status word HSI17 are used to indicate that the Check Weight is in either of those 2 areas. HI17.0 is set if the Check Weight is between check_lo_lo and check_lo, and HI17.1 is set if the Check Weight is between check_hi and check_hi_hi.
• The check_zero Mode parameter determines if a ZERO command also zeroes the check_zero weight.
• The check_mode parameter can be set to 1T1W, 1T2W, 2T1W, or 2T2W to put the unit in a "photo eye" mode.
• In a "photo eye" check_mode, the unit resets weight measurements after check_delay milliseconds from the falling edge of a photo eye sensor. Then, in 1T1W or 1T2W modes, after check_time milliseconds it will measure the check weight.
• In 2T1W or 2T2W modes there are 2 photo eye inputs, and the weight measurement takes place on the rising edge of the 2nd photo eye.
• In 1T2W and 2T2W modes the rising edge of the 1st photo eye input is used to trigger the sampling of the "check low weight"
• When in "photo eye" check_mode, bit 4 of the second status word (HI17.4) is set when the falling edge of the photo eye is detected. Bit 5 (HI17.5) is set when the check_delay period expires. Bit 6 (HI17.6) is set when the check_time period exipires and a new check weight sample becomes available.
• If "photo eye" check_mode is to be used, a photo eye input should be MAPPED to a digital input. By default, it is set to the 1st digital input DI0.0, and the 2nd photo eye, if needed is set to DI0.1. Both of these inputs come from a digital I/O option card.