SPC Charts

the spc chart processor function helps analyze process data over a specified window and generate insights into the process performance and capability it calculates various statistical measures and assesses adherence to quality specifications using control charts and pre defined rules spc charts overview first, the target mean (default 100), window size (default 50), and timer interval need to be set the timer interval parameter ensures that even if the connected input tag is not polling, the spc chart will still publish data at the specified interval if the input is expected to publish at the expected rate, set the timer interval to 0 to disable the timer the current mean and standard deviation (stddev) are calculated based on the input data within the defined window upper specification limit (usl) and lower specification limit (lsl) are computed based on the current mean and standard deviation the process capability (cp) is calculated as the ratio of the difference between usl and lsl over six times the standard deviation (6σ) cpu (upper capability index) and cpl (lower capability index) are calculated to assess how centered the process is within the specification limits cpu = (usl avg) / 3σ, cpl = (avg lsl) / 3σ process performance (cpk) is calculated by determining the smallest value between cpu and cpl optionally, if valid data is present, the cpm and cpkm (which use the target mean) will be computed the chart will also output any nelson rule violations with a true flag indicating which rule number has been violated the rules are as follows rule1 one point is more than 3 standard deviations away from the mean rule2 nine (or more) points in a row are on the same side of the mean rule3 six (or more) points in a row are continually increasing or decreasing rule4 fourteen (or more) points in a row alternate in direction, increasing then decreasing rule5 two (or three) out of three points in a row are more than 2 standard deviations away from the mean in the same direction rule6 four (or five) out of five points in a row are more than 1 standard deviation away from the mean in the same direction rule7 fifteen points in a row are all within 1 standard deviation of the mean on either side of the mean rule8 eight points in a row exist, but none within 1 standard deviation of the mean, and the points are in both directions from the mean spc charts parameters parameters details window size defines the number of data points considered for calculations the window size affects the computation of the current mean, standard deviation, and specification limits target mean this represents the desired average value for the process it serves as a reference point for evaluating process performance against expectations time interval specifies the frequency at which the spc chart publishes data note when creating an analytics flow with spc charts processor, refer the docid\ h7fkyhww8xueztpnodsa6 guide for more details