Title:	High Voltage How To Supplement
file:	$ESALIB/doc/hv/howto-supplement
by:	zms
date:	6/24/2003

0.	Overview

Initial use of the HV control revealed a few problems.  These problems, implemented
fixes, and the impact on how to operate the program are described in this note.

1.	Problem I

1.1	Description

Turning HV on in a chassis, turns all defined channels on.
The expected behavior is to exclude the channels which are marked with the on flag
to be off.  This flag is the last field in a channel defining line in the hv.dat setup
file.  This problem was not present in the HV program used in E158 run II.  I have
introduced the problem when I implemented using the concept of groups for issuing
various commands to the CAEN HV chassis.

1.2	The Fix

This problem was fixed as follows.  Channels marked with the on flag in the hv.dat file
set to 0 are excluded from the list of channels in a group.  With this fix in place,
these marked channels are excluded from any HV operations.  That is, they cannot be
turned on or off, cannot be read, etc..  These channels have "absent" in the status
field in the "ChanStat" display, meaning that they are not available.

1.3	How to

A channel marked with the on flag set to 0 can be made available as follows:
 a. Modify the hv.dat file to change the on flag from 0 to 1,
 b. In the "HVControls" dialog select the chassis in the Chassis list for which
    channels were modified if the hv.dat file was modified for one chassis only.
   If channels were modified in more than one chassis, then select the module in
    Modules list which controls the chassis of interest.
 c. In the HV program click on "More..." push button, this will bring the "Command"
    dialog.
 d. In the Command dialog select the "Purge Group" command from the Command options
    menu.
 e. In the Command dialog select the proper scope from the Scope options menu.  That
    is, if you want the command be executed in one chassis only, then the Chassis
    scope is appropriate.
 f. Finally, click Okay button.  You need to wait for at least 10 seconds before
    going to the next step.  How long should you wait?  When the group is purged
    or deleted, reading channels from the deleted group will fail.  When that
    happens, you should see messages in the logger, which look somewhat like this:
	"HVNetCliX::_done: mix=x,cix=y,chn=255,f=17(18),..."
    where mix is the module index and cix is the chassis index; these have numeric
    values like 1,2,3, etc..
    If you see these messages appearing with regularity, you have waited long enough.
 g. Restart the HV program.
 h. If all went well, you should now be able to control the previously unavailable
    channels.

2.	Problem II

2.1	Description

During one of the owl shifts, one of the two HV chassis tripped.  The HV program
continued reading status of all channels in both chassis, but the voltage values
were all 0's from one of them.  The HV program did not thing there was anything
wrong with that.  A few hours later someone noticed that there was a problem...

2.2	The Fix

Extensive modifications were needed in a number of software modules to fix this
problem.  Now the HV program will generate errors when the following conditions
are present:
 a. The software status of a channel is on and the hardware status of the channel
    is off.  This condition arises when the HV chassis or a single channel trips.
 b. A HV on command was executed and a channel fails to transition to the hardware
    status on within three consecutive checks of the channel.
 c. Various other failed conditions, like over-voltage, out of tolerance, trip, etc.

The failed channels are now displayed in red in the ChanStat display.  Two new fields
are added to each line showing the channel status.  These are labeled "soft" and "hard"
and stand for software on status and hardware on status.  When the HV on command is
executed, each affected channel is first marked as "req", meaning requested.  When
the hardware on status becomes "on" then the software on status is upgraded to "on"
as well,  The software on status remains "on" until the HV off command is executed
or the program is restarted.  When the program is restarted, the software on status
is set to match the hardware on status for each defined channel.

2.3	How to

The only new thing here is how to clear the condition when the software on status
is on and the hardware on status is off.  In this situation, it is necessary to
force the chassis or channel to off state by clicking the appropriate Off button
on the HVControls dialog.  After the error condition clears, the chassis or
channel can be turned back on.

A brief review of the toggle buttons on the HVCOntrols dialog may be useful.
 Read	if it is off, hv program does not issue channel voltage, current, and
	status read commands to the ioserv program.
 Check	when it is on, hv program periodically checks all available channels.
	The checking includes: 1. do the soft and hard on states agree, 2. did
	the channel status word indicate some abnormal hardware condition, 3. and
	finally, is the read voltage within tolerance.  The checking is done
	only when the Read is on.
 ErrOn	when it is on, hv program displays errors in the logger pane in the main
	window and also writes these errors to a log file.  Turn this off to
	suppress error messages.
 ErrSnd	when it is on, hv program sends error messages to DAQCntrl program.
 UseOn	At this point it became rather useless and I should remove it from
	the dialog.