LTC Temperature Controller Set-up Procedure

This page describes the set up of a cryostat for operation with the LTC controller and the SET_CONDUCTUS program.

Philosophy

With the present system, we try to achive maximum flexibility in setting up and operating any cryostat/controller combination. For proper operation, four parts need to be set up correctly:
  • Cryostat fittet with one or more Control Sensors and Heaters
  • LTC Controller fitted with Temperature Sensor Calibration Tables and PID Tables
  • LTC Controller Memory Look-Up Table reflecting the LTC memories in a text file for reference to the SET_CONDUCTUS program.
  • Sample Holders Look-Up Table defining in a text file the way sensors and heaters are combined to one or more control loops.
When initializing the system via SET_CONDUCTUS, the program presents you with the cryostats/sample holders and their respective control modes from the Sample Holders Look-Up Table for selection and the PID tables from the LTC Controller Memory Look-Up Table for assignment to the selected control loops.

1. Sensor Calibration Tables

1.1 Sensor Calibration Tables Archive

Located on NT Domain LMU group disk 
\\PSI10\G_1610\Temperature Sensors
A separate directory for every sensor class exists: 
CGR1       Carbon-Glass Resistance Sensors
CX10       Cernox Resistance Sensors
PT1	   Platinum-100 Resistance Sensors
STANDARD   Standart Curves (e.g. Standard Curve 10 for Silicon Diode Sensors)
TG120      GaAlAs Diode Sensors
Decommissioned (dead, burned, etc.) sensors are stored in the respective [.OLD] subdirectories.

For each Calibration Table, two ASCII file versions are available: 

.TAB	  Raw Table as supplied by manufacturer
.LTC	  Table for download to LTC controller with SET_CONDUCTUS, 
          fitted with all necessary parameters and control characters.

2. LTC Controller

If group logical CONDUCTUS_USER is defined as 
  $ DEFINE /GROUP CONDUCTUS_USER MASTER
calibration tables may be downloaded, cleared or shown interactively when Modify/Set Device/Conductus is selected in the MODAS run control menu. 
  $ DEASSIGN /GROUP CONDUCTUS_USER
hides this functionality.

2.1 Installing Temperature Calibration Tables

2.1.0 Check the Calibration Tables available in the LTC Controller

Check these tables either manually or remotly by running the command procedure:

@ED:[COM]SET_CONDUCTUS DOWNLOAD SHOW ALL

2.1.1 Downloading Temperature Calibration Tables

  • Make sure, the .LTC versions for all Calibration Tables to be downloaded reside in the ED:[DAT.LTC] directory of the area machine. If necessary, transfer them from the Calibration Table archive (see 1.).
  • The LTC controller accepts a maximum of 16 User Calibration Tables. Make sure, enough free memory slots are available. User Calibration Tables may be cleared from LTC memory. The indices of the Calibration Tables following the deleted table in the list will be decreased. When a User Calibration Table is downloaded it will always be appended at the end of the list.
  • Modify the file LTC_'Serial Number'_DWNLD.COM in ED:[DAT.LTC] to make it download the Tables needed. And ONLY those. See an example of a download command procedure.
  • Run the LTC_'Serial Number'_DWNLD.COM command procedure.
  • It is necessary to manually check each one of the downloaded tables on the LTC. Otherwise the table will not be activated and may therefore not be used.

2.1.2 Updating the LTC Look-Up Table

  • Update the appropriate LTC Look-Up Table LTC_'Serial Number'.TAB in ED:[DAT.LTC] to make it reflect precisely the calibration tables memory list on the LTC controller.

2.1.3 Updating the Sample Holders Look-Up Table

  • If you have replaced a control sensor: Update the appropriate Control Mode(s) for your cryostat/sample holder in ED:[DAT.LTC]SAMPLE_HOLDERS.TAB. Replace all old Sensor Names with the new Name as it appears on the LTC User Calibration Tables memory list.
  • If you have added a control sensor and/or heater: Extend the Control Modes for your cryostat/sample holder in ED:[DAT.LTC]SAMPLE_HOLDERS.TAB.

2.2 Installing PID Tables

2.2.1 Creating PID Tables

  • PID Table Files must be located in ED:[DAT.LTC] and should have a File Name according to 'PID Table Name'.PID (e.g. TEST_PID.PID)
  • The file structure is: 
    300.3 1 2 3 0.23 0   ! set_point_1 P_1 I_1 D_1 P0_1 TPMAX
250.0 ...........    !
.................    ! set_point_n
$                    ! download terminator
    A maximum of ten break points are allowed, listed with the temperature in descending order. The table ends with the terminator $.

2.2.2 Downloading PID Tables

Download your table using the DCL command 
@ED:[COM]SET_CONDUCTUS DOWNLOAD PIDTABLE 'PID Table Name'.PID 'PID Table Index'
Example: 
@ED:[COM]SET_CONDUCTUS DOWNLOAD PIDTABLE TEST_PID.PID 1
downloads the PID Table ED:[DAT.LTC]PID_TABLE.PID as PID Table 1 to the LTC controller.

Verify the PID table values stored in the LTC controller memory before setting the controller to control mode the first time!

2.3 Setting the Filter Time

Remember to set the appropriate Filter Time for your system manually at the LTC controller (Setup - Display - Setup Input Filter).

2. LTC Controller Memory Look-Up Table

The LTC Controller Memory Look-Up Table LTC_'Serial Number'.TAB in ED:[DAT.LTC] reflects for every single LTC controller the contents of the Calibration Tables and PID Tables memory and some other parameters like the device GPIB address.

See an example of a LTC Controller Memory Look-Up Table.

When installing a cryostat sytem, make sure the Memory Look-Up Table for the LTC controller in use is located in ED:[DAT.LTC] of your area machine and precisely reflects the contents of the memories.

3. Sample Holders Look-Up Table

The Sample Holders Look-Up Table ED:[DAT.LTC]SAMPLE_HOLDERS.TAB defines all existing cryostats/sample holders and their respective Control Modes in one file. It containes:
  • The Name of a Cryostat/Sample Holder
  • If the system is operated in single (single_loop) or two-loop mode (two_loop).
  • The Sensor Location Name (e.g. Diffuser_Sensor)
  • The Sensor Name of the Sensor allocated to a Sensor Location (e.g. CX1050SD_X03458)
  • To which LTC channel a sensor is assigned.
    • First line: Channel 1 = Heater Output
    • Second line: Channel 2 = Analog Output
    • Exception: If the keyword analog is given on the first line as fourth column, Analog Output is assign to Channel 1. If the keyword heater is specified on the second line as forth parameter, Heater output is assigned to channel 2.
    • If keyword A=pid_table_name or H=pid_table_name is specified as fourth parameter, pid_table_name will be assigned to H(eater) or A(nalog), respectively, during LTC setup.
See an example of SAMPLE_HOLDERS.TAB.

When installing a cryostat sytem, make sure SAMPLE_HOLDERS.TAB is located in ED:[DAT.LTC] of your area machine and up to date.

3. Control Modes

3.1 Updating a Control Mode

This applies if you have replaced a control sensor.

3.1.1 Updating the Sample Holders Look-Up Table

Update the appropriate Control Mode for your cryostat/sample holder in ED:[DAT.LTC]SAMPLE_HOLDERS.TAB.

3.2 Creating a new Control Mode

This applies if you have introduced an additional control sensor and/or heater or if you want to pair a control sensor with a different heater.

3.2.1 Extending the Sample Holders Look-Up Table

Extend the Control Modes for your cryostat/sample holder in ED:[DAT.LTC]SAMPLE_HOLDERS.TAB

Appendix A: Calibration Table File Names and Sensor Names

Note that Calibration Table File Names and Sensor Names are not identical. Sensor Names, as they appear in the .LTC versions of the Calibration Table Files, on the LTC controller and in the SAMPLE_HOLDERS.TAB Look-up Table carry the package type as additional parameter, if applicable.

The Calibration Table File Names follow the scheme: 

'Short Sensor Type Code'_'Serial Number'.'File Type'
The Sensor Names follow the scheme: 
'Full Sensor Type Code''Package Type Code'_'Serial Number'

Sensor Type Codes

Short	Full		Type

CGR15	CGR1500		CGR-1-500
CGR11	CGR11000	CGR-1-1000
CGR12	CGR12000	CGR-1-2000
CX103	CX1030		CX-1030
CX105	CX1050		CX-1050
PT111	PT111		PT-111
TG120	TG120		TG-120
See manufacturer's literature for specifications.

Package Type Code

CU
LR
P
SD
See manufacturer's literature for specifications.

Sensor Serial Number

Sensor Serial Number, typically starting with a one-letter code followed by 4- to 5-digit numbers. 
Sensor Class	Code	Typical no. of digits following
CGR		C	5
DT		D	5
PT		P	5
CX		X	5
TG-120		none	4

File Type

.TAB	Raw Table as supplied by manufacturer
.LTC	Table for download to LTC controller, fitted with all necessary 
        parameters and control characters.
Most Calibration Table files are created by means of OCR from the hard copy of the manufacturer's calibration table and have been carefully checked for errors. However, typos are not to 1O0% excluded...