Hello All!

I've been putting together several SQC Charts with the tag, upper, lower, center settings to present the data in the Chart. I noticed when I use a filter equation, the chart immediately loses its data graphically once one presses the Play button. If I remove the filter equation, and push play the data is shifted but remains displayed in the graph. I am scratching my head about the Filter equation. The equation used is ('Tag' = 100) so, when Tag equals 100, it is my understanding it will acquire 20 samples (Samples before end time) to plot as soon as the Tag equals 100. My calculation Basis is set on Event. Would someone elaborate when it is best to utilize the "Time" Calculation Basis for the SQC Chart? I noticed one can set the Calculation Period, Sample Period, and Start Time of Sample. In my opinion, I would think the Start Time of Sample would be automatically calculated once Tag equals 100.

Thanks Again!

Hello Robert,

The Calculation Basis and Filter Equation are two separate features of PI SQC. The Filter Equation simply will only show the data that your equation specified over the Plot Time. So, if you have 'Tag'=100, the only points shown on the chart will be when the tag equals 100 over the plot time. If there are not enough values within that plot time, it will not be able to do the appropriate calculations thus showing a blank chart.

Calculation Basis options define the mathematical parameters used for sampling. A Time-based calculation uses samples for every Sample Period and performs a calculation for every Calculation Period, determined whenever samples matching the Sample Size are collected. An Event-based calculation uses every raw data value associated with the tag. For event-based calculations, Calculation Period, Sample Period, and Start Time of Sample are disabled.

Please check out our Live Library for help with SQC.