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Entry  Mon Nov 26 21:58:08 2018, Jon, Omnistructure, , Serial Vacuum Signals GP307_relays.jpeg
    Reply  Tue Nov 27 17:06:51 2018, Steve, Configuration, VAC, Agilent 84FS turbo installed as TP2 
Message ID: 14320     Entry time: Mon Nov 26 21:58:08 2018     Reply to this: 14322
Author: Jon 
Type: Omnistructure 
Subject: Serial Vacuum Signals 

All the serial vacuum signals are now interfaced to the new digital controls system. A set of persistent Python scripts will query each device at regular intervals (up to ~10 Hz) and push the readings to soft channels hosted by the modbus IOC. Similar scripts will push on/off state commands to the serial turbo pumps.

IP Addresses/Comm Settings

Each serial device is assigned an IP address on the local subnet as follows. Its serial communication parameters as configured in the terminal server are also listed.

Device IP Address Baud Rate Data Bits Stop Bits Parity
MKS937a vacuum gauge controller 9600 8 1 even
MKS937b vacuum gauge controller 9600 8 1 even
GP307 vacuum gauge controller 9600 8 1 even
GP316a vacuum gauge controller 9600 8 1 even
GP316b vacuum gauge controller 9600 8 1 even
N2 pressure line gauge 9600 7 1 odd
TP2/3 9600 8 1 none

Hardware Modifications

  • Each of the five vacuum gauge controllers has an RJ45 adapter installed directly on its DB9/DB25 output port. Because the RJ45 cable now plugs directly into the terminal server, instead of passing through some additional adapters as it formerly did, it was necessary to reverse the wiring of the controller TXD and RXD pins to Ethernet pins. The DB9/25-to-RJ45 adapters on the back of the controllers are now wired as follows.
    • For the MKS controllers: DB2 (RXD) --> Eth4;  DB3 (TXD) --> Eth5;  DB5 (RTN) --> Eth6
    • For the Granville-Phillips controllers: DB2 (TXD) --> Eth5;  DB3 (RXD) --> Eth4;  DB7 (RTN) --> Eth6
  • I traced a communications error with the GP307 gauge controller all the way back to what I would have suspected least, the controller itself. The comm card inside each controller has a set of mechanical relay switches which set the communications parameters (baud rate, parity, etc.). Knowing that this controller was not part of the original installation, but was swapped in to replace the original in 2009, I pulled the controller from the rack and checked the internal switch settings. Sure enough, the switch settings (pictured below) were wrong. In the background of the photo is the unit removed in 2009, which has the correct settings. After setting the correct communications parameters, the controller immediately began communicating with the server. Did these readouts (PRP, PTP1) never work since 2009? I don't see how they could.
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