User manual

PID Loop Operation
(DL450 Only)
Maintenance
8--59
PID Loop Operation (DL450 only)
DL405 User Manual, 4th Edition, Rev. A
The normal state for the ramp/soak control bits is all zeros. Ladder logic must set
only one control bit at a time.
S Start y a 0 to 1 transition will start the ramp soak profile. The CPU
must be in Run Mode, and the loop can be in Manual or Auto Mode. If
the profile is not interrupted by a Hold or Jog command, it finishes
normally.
S Hold y a 0 to 1 transition will stop the ramp/soak profile in its current
state, and the SP value will be frozen.
S Resume y a 0 to 1 transition cause the ramp/soak generator to resume
operation if it is in the hold state. The SP values will resume from their
previous value.
S Jog y a 0 to 1 transition will cause the ramp/soak generator to truncate
the current segment (step), and go to the next segment.
You can monitor the Ramp/Soak profile status
using other bits in the Ramp/Soak Settings
V+33 word, shown to the right.
S R/S Profile Complete y =1 when the
last programmed step is done.
S Soak PV Deviation y =1 when the error
(SP--PV) exceeds the specified deviation
in the R/S table.
S R/S Profile in Hold y =1 when the pro
file was active but is now in hold. Ramp/
Soak Settings V+33.
The number of the current step is available in
the upper 8 bits of the Ramp/Soak Settings
V+33 word. The bits represent a 2--digit hex
number, ranging from 1 to 10. Ladder logic
can monitor these to synchronize other parts
of the program with the ramp/soak profile.
Load this word to the accumulator and shift
right 8 bits, and you have the step number.
The starting address for the ramp/soak table
must be a valid location. If the address points
outside the range of user V--memory, one of
the bits to the right will turn on when the
ramp/soak generator is started. We recom-
mend using DirectSOFT to configure the
ramp/soak table. It automatically range
checks the addresses for you.
It’s a good idea to test your ramp/soak profile before using it to control the process.
This i s easy to do, because the ramp/soak generator will run even when the loop is in
Manual Mode. Using DirectSOFT’s PID View will be a real time--saver, because it
will draw the profile on--screen for you. Be sure to set the trending timebase slow
enough to display completed ramp--soak segment pairs in the waveform window.
Ramp/Soak Profile
Monitoring
Ramp/Soak
Programming
Errors
Testing Your
Ramp/Soak Profile