Replay display in Baume mode |
Replay display in g/ml mode |
|
Replay display in Baume mode |
Replay display in g/ml mode |
Etcher process problems are often difficult to diagnose. Each cycle of etcher activity happens over many minutes making it hard to observe and recall accurately. Often the problem occured at some time in the past, perhaps several days ago. An automatic process log which retains process data until it is needed for analysis greatly simplifies process diagnostics. The Model 136 Process Monitor features automatic process logging and instant replay functions. Each time an event occurs (an event is a change in any monitored condition: density, mode, alarm, etc.), the monitor stores the current process status information including the time and date of the event in flash memory. Flash memory is capable of retaining its data without any backup power source.
Process logging goes far beyond mere data logging. Data logging records process variables on a repetitive, timed schedule whether or not there have been changes. Thus it fills much of the memory with the same unchanged data over and over. While it is doing this, if there is any process activity between the data collection times they will not be recorded. Process logging in contrast records every change in process variables and does not waste memory capacity recording that nothing has changed. Replay is much more efficient because the user does not have to wade through repetitive "no change" data sets to sort out the few which are interesting because they show change. All the data sets in the automatic process log show process variable changes.
The 136 monitor can store 100,000 process events, or several months
of process data. Once this data is stored, the replay function allows
the
user to review it. Depressing the << button begins the review,
and
continued presses increase the speed of the replay. During the replay,
the LCD display shows the density, deviation, time, and date of the
past
events. Also, found in the lower right corner of the LCD are the Pump
On
indicator (P), Alarm On indicator (A), and the Manual Mode indicator
(M).
At any point during the rewind, the user can press the >> button
to pause the replay. Additional presses of the >> button begin
moving
forward through the history file or rewind can be continued by pressing
the << button again. Pressing the END button will cancel the
replay
function and return to the current display mode. By reviewing this
stored
information, the etching process can be better managed and production
problems
easily identified.
Process logging and the replay feature are
patented under US Pat. # 6,487,462.
During replay, stored process data is also output to the RS232 port allowing it to be transfered to a PC for more extensive analysis and display.
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