Controlling the Mass Flow Controllers for the BoNuS Detector

K. Giovanetti, G. Niculescu. I. Niculescu, James Madison University Physics

 

 

Standard Operation: For standard operation the top four toggle switches should be on indicating that the program should attempt to control both MFCs, write data to the Epics database and update the MFC settings based on new EPICS values.

 

The Bonus gas system is regulated by two remotely controlled Mass Flow Controllers, MFCs. The MFCs were manufactured by Qualiflow. The MFCs have been calibrated for Helium and DME.  They are mounted on a panel located on the target frame in the experimental hall. Communication with the MFCs is done using RS232 connections.  The actual communication language used over the RS232 line is a special protocol specifically designed for instrument control. The MFCs come with software support so that MFC control does not need to be done using this primitive code, the lowest level. 

 

To operate the MFCs [AFC 80MD mass flow controllers] one needs:

 

  1. Power [D082D/ZM  Seven Star]
  2. Communication port. [RS232, separate port for each MFC]
  3. Software program. [LabView, DigiSoft]

 

 

Basic layout is shown below.

 

 

 

The computer is a standard PC running Windows 2000. The computer is mounted on one of the target frames in the experimental hall.  The computer can be reached using VNC a client/server virtual network. The VNC server software must be running on the PC. (The VNC server should start by default on a boot.)

 

http://www.tightvnc.com/

PC internet address: 129.57.167.246   [PORT:5800]

 

One can access the desktop of the computer using a web browser

(http:// 129.57.167.246:5800 ) or a VNC viewer. You will be prompted for a password.

 

On the computer (computer name in the browser=miller_1245) two programs for control are available, either the manufacturers stand alone package Digisoft or a LabView program. The Digisoft program has  more MFC conrtol and monitoring features but has no EPICS component. For example,the Digisoft program can set the MFCs to run in either analog or digital mode. This feature cannot be accessed with the LabView program. The Digisoft program can talk to one and only one MFC at one time. The choice is made using the COM port pull down menu on the first screen.  Choose either port 1 or 2 and then click to the regulation screen (Top Tab).  The program scans the port for a MFC and then reports on what it finds.  User’s can simply change ports to contact another  MFC and  the user can alternate back and forth as necessary. More information can be found at

http://www.qualiflow.com/us/s_notes.html

 

A Labview program was developed and integrated with EPICS so that data could be stored in the data stream and so that MFCs could be set through  EPICS channel access.  This program combines the LabView tools that were provided by Qualiflow with a Windows based IOC developed by Willem Blokland for the Spalation Neutron Source.

 

http://www.sns.gov/diagnostics/documents/epics/LabVIEW/SNS_LabVIEWEPICS.html

http://www.sns.gov/diagnostics/documents/epics/Downloads/downloads.html

 

The program can be started by choosing the Labview icon. You CAN NOT run the Digisoft program and the labview program simultaneously because they both would address the same com ports. However the adjusted settings of either program remain in force unless the new program makes a specific change. In considering the operation of the MFCs one should remember that the MFCs when powered keep their settings and operate independently of whether or not the control program is running.  This enables either program to alternate between the two MFCs and allows one to set values using one program and then switch to the other. For example, the MFC needs to run in digital mode to be controlled by the Labview software. If the MFC is not currently in digital mode it can be changed using the Digisoft program (selection on Regulation window). The labview program can then be run after the Digisoft program is exited.

 

The LabView program has been designed to run with front panel inputs that determine program flow. To facilitate the explanation the following modes of operation are important and are determined by the upper panel ENABLE rocker switch setting:

 

 

 

 

MFC1 operational: [MFC1 Available = TRUE]

The MFC is present and powered-up therefore read and writes will be executed. Otherwise the program ignores the MFC.

 

MFC2 operational: [MFC2 Available = TRUE]   

The MFC is present and powered-up therefore read and writes will be executed. Otherwise the program ignores the MFC.

 

Epics  ON: [Use Epics =TRUE]   

The Epics IOC software is started.  Data recording to the EPICS database will be performed.

 

Epics OFF: [Use Epics =FALSE]   

The Epics software is  not intialized.  EPICS database ignored.

 

Local mode: [Epics will set MFC =FALSE]   (MFC Setpoints controlled LOCALly from the front panel.)

Epics may be configured to read only or not used at all. If Epics is started it is not allowed to update the MFC setpoints.  Setpoints are changed by values in the Req Setpoint window on the front panel and loaded using the write button. 

 

Epics Write Mode: [Epics will set MFC  =TRUE]   

Epics is configured to allow a change  in the setpoint based on epics values.  The database values are used to update the Req Setpoint window and the write is performed as part of the MFC sequence. The sequence of events is ordered so that the MFC current setpoint is read, and then this setpoint as read from the MFC is loaded as the intial value for the EPICS database. Epics On must be set in order to use this mode.

 

 

In local mode (either  “Epics on” Local Mode or “Epics Off” Local Mode) the MFC setpoint is loaded into the MFC by pressing a write button otherwise the program just retrieves the values (reads the MFC). When the program starts the MFC settings are not changed only read. The setpoint value ( Req Setpoint) should be considered arbitrary and the user should examine the current MFC setting in the MFC setpoint window and carefully entering a reasonable value in the Req Setpoint window before hitting the write button.  A new setting can be entered in the window and a write initiated with the write button.

 

 For each MFC there are three important values shown on the control panel.

  1. Req Setpoint
    1. Local Control: Adjustable value that represent the value that the MFC setpoint will be changed to if the write button is pressed.
    2. Epics control: The values is set by reading the database and then the write function is enabled. This value will  be periodically written to the MFC. To ensure proper control the program reads MFC’s current set point once at the start and updates the database setpoint ReqSetpoint value and finally uses this database setpoint to change the MFC.

 

  1. Setpoint:
    1. The value that the MFC has stored as its required setpoint.
  2. Flow
    1. The value returned by the MFC as the flow rate.

 

In addition there are some diagnostic values on the control panel that show the current Epics database values

 

 

 

 

 

and the current MFC values.

 

 

 

 

 

For a typical startup the program should

  1. Start Epics
    1. Load initial values.
  2. Connect to MFC 1
    1. Write info to valves when a “write button”. is pushed
    2. Get all the current information from MFC

 

  1. Connect to MFC 2
    1. Write info to valves when a “write button”. is pushed
    2. Get all the current information from MFC

 

  1. Update epics database values and retrieve any new setpoints.

 

A flow chart depicting this follows:

Internally the  labview program uses variables, controls and indicators to control data and program flow. Some of the important variables can be found in the following table.

The I’s are indices to the database. The D’s are the fron panel diagnostic diplays for the database the M’s are the MFC values read back from the MFCs.

MFC#

index

dbdisplay

MFCcntl

 

labview

 

 

 

 

 

 

1

I1Setpoint

D1Setpoint

M1Setpoint

orange

sgl

1

I1ReqSetpoint

D1ReqSetpoint

M1ReqSetpoint

orange

sgl

1

I1Flow

D1Flow

M1Flow

orange

sgl

1

I1ValvNo

D1ValvNo

M1ValvNo

blue

U16

1

I1Alarm

D1Alarm

M1Alarm

blue

U8

1

I1AlarmReset

D1AlarmReset

M1AlarmReset

green

I16

1

I1Override

D1Override

M1Override

pink

string

1

I1ReqOverrride

D1ReqOverrride

M1ReqOverrride

pink

string

1

I1ManID

D1ManID

M1ManID

pink

string

1

I1ProdID

D1ProdID

M1ProdID

pink

string

1

I1Serial

D1Serial

M1Serial

pink

string

1

I1Type

D1Type

M1Type

pink

string

1

I1SoftVer

D1SoftVer

M1SoftVer

pink

string

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

I2Setpoint

D2Setpoint

M2Setpoint

 

sgl

2

I2ReqSetpoint

D2ReqSetpoint

M2ReqSetpoint

 

sgl

2

I2Flow

D2Flow

M2Flow

 

sgl

2

I2ValvNo

D2ValvNo

M2ValvNo

 

U16

2

I2Alarm

D2Alarm

M2Alarm

 

U8

2

I2AlarmReset

D2AlarmReset

M2AlarmReset

 

I16

2

I2Override

D2Override

M2Override

 

string

2

I2ReqOverrride

D2ReqOverrride

M2ReqOverrride

 

string

2

I2ManID

D2ManID

M2ManID

 

string

2

I2ProdID

D2ProdID

M2ProdID

 

string

2

I2Serial

D2Serial

M2Serial

 

string

2

I2Type

D2Type

M2Type

 

string

2

I2SoftVer

D2SoftVer

M2SoftVer

 

string

 

 

 

 

 

 

 

Variable used for program control include:

 

MFC1Present

T/F

boolean

control

set by user (default now is false)

 

use/skip MFC port open and reading

MFC2Present

T/F

boolean

control

set by user (default now is false)

 

use/skip MFC port open and reading

UseEpics

T/F

boolean

control

set by user (default now is true)

typically chosen and fixed

true starts epics in "init" step

EpicsSet

T/F

boolean

control

set by user (default now is false)

makes epics the source of new settings

you can disable and then use the front panel to set the MFCs

Epics IOC Started

T/F

boolean

indicator

False at start

set at completion of the initialaization of IOC

 

MFC1active

T/F

boolean

indicator

False at start

true only in the valve  1 process

 

MFC2active

T/F

boolean

indicator

False at start

true only in the valve  2 process

 

Login Verified

T/F

boolean

control

False at start

currentl disabled

repeats login until verified

Epics write 1

T/F

boolean

 

False at start/ set false if Epics set is False

true after the DB req has been loaded

controls whether a MFC setpoint is written

Epics write 2

T/F

boolean

 

"""""

"""""

"""""

MFC1Read

T/F

boolean

control

false/set to true after MFC read

"none" loop waits until true to set db (sets it false),"valve1/2" loops sets true at end

controls the time when the db values are updated to only after a MFC read.

MFC2Read

T/F

boolean

control

'''

"""""

'''

Init DB REQ 1

T/F

boolean

control

false until the MFC read and DB set to current read value

reset if EpicsSet is False so that you can go back to front panle control.

used to intialize the database to the cirrent MFC setting. Need to read MFC and load this setpoint into the DB.

Init DB REQ 2

T/F

boolean

control

''

''

'