Instron stress rig

Setup

The Instron stress rig is a National Instruments GPIB device. It requires some special setup to get going:

• The Ethernet GPIB box requires a driver for the LabVIEW driver. This can be installed from \olympic\Babylon5\Public\GHowells\NI GPIB
• Run the installer as an administrator, accept the defaults. It will unzip, then install. It takes a while to install.
• You then need to set up the ENET box, Gareth or Freddie can show you how to set this up
• LabVIEW vi located at : C:\LabVIEW Modules\Instruments\ENGINX\Stress Rig\Stress Rig - System Functions.llb\Stress Rig - 100 kN Stress Rig.vi
• On running the vi, you will get some dialogs – just ok through them. The indicators should then be updating.
• If you can't get the labview to talk at all, the stress rig might need to be power cycled. @GDH-ISIS and @FreddieAkeroyd know how to do this. The basic instructions are below:
  • Turn off the stress rig PC (white/beige pc located under the stress rig)
  • Turn off the GPIB box (this looks similar to a router, located under the stress rig near to the stress rig PC)
  • Wait a few seconds
  • Turn on the stress rig PC
  • Wait several minutes. The stress rig will go through a self-test phase. You need to wait for this process to be complete.
  • If you need to calibrate the rig, the following sequence on the console should be used: "Load channel: setup" -> "cal" -> "cal" -> "auto" -> "go" (if you are unsure about this ask the scientists)
  • Turn back on the GPIB box.
  • After the GPIB box has been turned on for a short time (e.g. 1 minute) the driver (LabVIEW or IOC) should be ready to connect.
  • GPIB box LEDs - PWR should be orange, LNK 10/100 should be green. Other LEDs will be flickering depending on connection. Box might have a slightly dodgy connection (not sure about this, but check it) so ensure the LEDs are as described.

Driver

The stress rig driver uses the following DB files:

• controls.db - provides basic PVs such as stopping the rig, getting the status, changing control channels, etc
• controls_channel.db - provides PVs that are common to each channel (Position, Stress, Strain), e.g. setpoints, readbacks, step times
• controls_channel_specific.db - add on PVs for the above - used to add PVs for some channels that don't exist on others
• controls_waveform.db - provides the PVs dealing with the waveform generator
• logging.db - provides the PVs to do with logging to a file

The protocol is defined in C:\Instrument\Apps\EPICS\support\instron\master\instronSup (see https://github.com/ISISComputingGroup/EPICS-instron/blob/master/instronSup/devinstron.proto)

Gotchas / Unusual things

• Every "write" command (commands starting with C or P) must be preceded by P909,1 (switch to computer control mode) and C904,0 (disable watchdog). For convenience there is the setControlModeCom function in the protocol file which does these for you.
  • If you forget to do this, the rig's hydraulics will trip, requiring a physical button push to reset them
• Every "write" command (commands starting with C or P) must be followed by P909,0 (switch to front panel control mode)
• We have had issues with PVs dropping off to zero while being read from the stress rig. To solve this, use a :RAW record which does a read, and monitor it using CP from another record. This fixes the issue of getting zeroes.
  • Might be a bug in EPICS and/or the interface between the VISA driver and EPICS. At the moment the above solution seems to be the easiest way to cure the symptoms.
• PVs in the stress rig don't scan by themselves typically, they are triggered from one of two read loops:
  • READ_SLOW scans at 1 Second interval
  • READ_VAR reads at a rate that can be varied by the user
  • In the READ_VAR loop the .1 Second option has been removed, this is too fast for the rig to handle
• If something works in LabVIEW but not in EPICS, or vice-versa, NI Input/Output trace (NI Spy) can be very useful to compare the traffic and spot any differences.