You are here: NI Home > Support > Product Reference > Manuals > LabVIEW 8.6 Datalogging and Supervisory Control Module Help

Owning Palette: Control Charts VIs

Installed With: Statistical Process Control Toolkit

Computes points and limits for individuals x and moving Range charts. These are control charts for charting mean and moving range. This VI computes for a moving range from n consecutive observations. By default, n is two. Optionally, you can choose a range of indices for individuals to use and indices of individuals to ignore in the control calculation. The actual number of individuals the VI uses to calculate the control limits is also output. By default, control limits are calculated from the input samples. You can also calculate control limits from standard values by wiring the chart limit src input.

Details  

	chart limit src specifies whether or not to use standard values for the chart limit calculations. If unwired, this cluster defaults to the common case where the chart limits are calculated from the data in the input sample array. You do not have to wire this cluster unless you want the chart limits to be calculated from standard values. When using standard values, the center line for the X-bar control chart, X-bar-bar, is set to std mean, and the center line for the s control chart, s-bar, is set to std s0, or std sigma*c4. source selects one of three choices for source of chart limits calculation: 0 from data—(Default) chart limits are calculated from samples. 1 use std mean, s0—chart limits are calculated from standard mean and s0. 2 use std mean, sigma—chart limits are calculated from standard mean and sigma. std mean is the standard mean value to use in calculating chart limits from standard values. std R0/sigma is the standard R0 or standard sigma to use in calculating chart limits.
	individuals x are the individual observations (or samples of subgroup size 1) on which to compute control limits.
	index spec is used to choose a range of samples in c to use for the control limit calculation. If you do not wire this cluster, all elements in c input array are included in the control limit calculation. start index is the index of the first element of c to include in the control limit calculation. Default is 0 or index of the first sample in the c array. end index is the index of the last element of c to include in the control limit calculation. Default is 0 which selects the last sample in the c array.
	indices to ignore is the indices of samples to exclude from the control limit calculation. Excluding samples is useful for eliminating out of control points from the control limit calculation. By default, this is an empty array.
	std error multiplier (3) is the multiplier to use for the upper and lower control limits. Normally you leave std error multiplier unwired, and the VI sets the control chart limits to ±3.0 standard errors. The default is 3.0.
	n: sample size (2) is the number of individuals to use for the moving Range calculation. Min value is 2, max value is 25. The default value is 2.
	x-bar & mR-bar/d2 is an estimate of the process sigma (standard deviation) based on the average of the moving range between individuals included in the control limit calculation. x-bar is an estimate of the process mean based on the average of the individuals included in the control limit calculation. mR-bar/d2 is an estimate of the process sigma (standard deviation) based on the average of the moving range between individuals included in the control limit calculation.
	x is the individual observations. This is the array plotted on the x control chart.
	x chart limits contains the limits for the R chart. UCLx is the upper control limit for the x chart. CLx is the center line for the s control chart. CLx = x-bar. LCLx is the lower control limit for the x chart. standard error is the standard error associated with x-bar.
	moving range mR is the moving range of individuals {x[i], ...., x[i-n+1]}, where n is the sample size. This is the array plotted on the mR control chart.
	mR chart limits contains the limits for the R chart. UCLr is the upper control limit for the mR chart. CLr is the center line for the s control chart. CLr = mR-bar. LCLr is the lower control limit for the mR chart. standard error is the standard error associated with mR-bar.
	# individuals in calc is the number of individuals used in the control limits calculation.

x & mR Chart Details

The control limit calculations are as follows.If standard values are used for the control limit calculations, then

(x-bar) is set to std mean

(mR-bar) is set to std R0 or std sigma * d2, otherwise, X and mR are calculated from the input samples as specified by the index spec and indices to ignore inputs.