24 WATLOW Series 945 How to Use Data Communications
Chart & SPC
NOTE:
The time is printed
every 5th interval
(Int). The tempera-
ture variable (*) is
printed every 10th
interval.
One Int = 6 seconds.
Figure 12 -
Chart and SPC
Printout Example
100°F12575
PROCESSDATE: 01-01-90
******
CPKL = 1.36 CPKU = 1.32
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
***
*
*
***
*
*
***
*
*
*
*
*
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
***
*
*
*
*
***
*
101
100
99
101
(SPCA & SPCd only) (SPCA & SPCd only)
Set Point
Temperatur
e
01:00:01
01:00:31
01:01:01
01:01:31
01:02:01
01:02:31
01:03:01
01:03:31
Tim
e
Lower Control Limit
(SPCA & SPCd only) Upper Control Limit
(SPCA & SPCd only)
Set Point Variable
Temperature Variable
90
92
110
110
Maximum Excursion Maximum Excursion
CP = 1.34
(Any messages concerning tchanges in he system are printed here)
Temperature Variable

Chart and SPC Printout

Example: Log = SPCA, Int = 0.1

P = Process S = Set Points

The Chart and SPC (Statistical Process Control) format are very similar. The only

difference is the SPC output displays the lower (L) and upper (U) control limit.

They are calculated based upon the mean value of the process variable, and are

derived from 30 random samples taken over the selected time base (tbS), the

mean value used is from the previous timebase samples (ex. the mean from the

first 30 samples is used to compute the control limits for the second 30 samples

and so on for every sample period. If SPCA (Specification limits Absolute or SPCd

(spec. limits Deviation) is selected then the CPKL, CP, or CPKu values will also be

printed. If the variation in the process value is too small to calculate the control

limits, L and U and the message "Variation Insignificant" are printed. If at any time

the process value exceeds the control limits during a print interval, the maximum

process excursion value will be printed (if both L and U are exceeded, both maxi-

mum values will be printed) on the next line printed. At any time the control limits

can be locked in by setting CLUP to "no" . If CLUP = no, new control limits can be

set by CLUP = YEs.

(Any messages concerning changesin the system are printed here)