Sample annealing

Temperature reading precission

Depending on the sample materials and sample holder used, the K-type thermocouple) can be spot-welded to the sample (side or surface) or only touching it. In the latter case the real temperature might be higher. Be aware that the error can be as high as 10% of the read temperature in °C or 6% in K (for example 50 °C/K error at 500 °C/800 K. Alternatively, you can use a pyrometer but it would require a complicated calibration of emissivity.

 

Sample annealing controller

For annealing we use a costom-made annealing controller containing Delta Elektronika SM 70-AR-24 power supply and Eurotherm 3508 regulator. Required currents usually do not reach 15 A, depending on the sample holder and mounting used. The parameters of the regulation loop can be set using the iTools software provided by Eurotherm. The scope is to measure the sample temperature (by reading the voltage of the thermocouple) and regulate the annealing current in order to reach and keep the desired temperature.


annealing controller

 There are two modes of operation selectable by the switch:
  • KEEP TEMPERATURE: the feedback loop is active, the controller is trying to keep the temperature as set by the up/down arrows by regulating the annealing current, respecting the VOLTAGE LIMIT and CURRENT LIMIT set by corresponding knobs.
  • SET CURRENT MANUALLY: fhere is no feedback loop; the voltage and current are set by the corresponding VOLTAGE/CURRENT LIMIT knobs while the display shows the actual temperature, ignoring the desired temperature set by arrows.
Manuals of the Delta Elektronika SM 70-AR-24 power supply, Eurotherm 3508 controller and iTools software in PDF PDF



Computer interface

The Eurotherm unito can be also remotely controlled from the MSB-STATION computer via the iTools software.

The temperature can be graphically monitored by the OPC Scope feature refreshed once per second. The data can be logged into a file.
 3508 front panel

Unit selection (K/°C)

  1. On the controller press scroll button. The double arrow symbol up/down normally next to the set temperature will appear in front of the current unit.
  2. Using upd/down arrow buttons set the desired unit (C, K or F).
  3. Confirm with scroll button button or discard the change with page button button.
(You can also select the unit in the e Eurotherm iTools software on the MSB-STATION computer.)



Short annealing (flash)

  1. Move the sample to a safe position (not in front of the electron analyzer).
  2. Check that the CURRENT LIMIT is set to zero (fully counterclockwise).
  3. Switch the operation mode to SET CURRENT MANUALLY.
  4. Slowly increase CURRENT LIMIT by rotating the knob. Observe the current and voltage increase on the power supply, temperature increase on the temperature controller and/or heater glowing through the chamber viewport. Increase also VOLTAGE LIMIT if voltage starts limiting the output power.
  5. When you reach the desired temperature decrease the CURRENT LIMIT to zero.

Long annealing (keeping at temperature)

  1. Move the sample to a safe position (not in front of the electron analyzer).
  2. Check that the CURRENT LIMIT is set to zero (fully counterclockwise).
  3. Switch the operation mode to KEEP TEMPERATURE.
  4. Use the up/down arrow buttons on the temperature controller to set the desired temperature (shown after up/down on the display, e.g. setpoint).
  5. Slowly and step-wisely increase CURRENT LIMIT. Observe the current and voltage increase on the power supply, temperature increase on the temperature controller and/or heater glowing through the chamber viewport. Increase also VOLTAGE LIMIT if voltage starts limiting the output power.
  6. When the desired temperature is reached the controller starts regulating the current in order to keep the temperature. Oscillations around the set value may appear.
  7. Start the timer.
  8. After a while, when stabilized, write down the voltage and the current used. You may use these parameteres for setting of the limits during another annealing at the same temperature in the future.
  9. When the time is over set CURRENT LIMIT to zero (fully counterclockwise).

Programmed annealing

More complicated annealing procedure can be programmed using the Programmer feature of the iTools software, e.g. a temperature ramp 5 K/s up to 600 K, dwell 10 min, cooling below 400 K and repeating such cycle 3 times. Once programmed, use the Run/Hold button on the Eurotherm unit for:
  • start (double short press) - the display will show RUN
  • pause or continue (single short press) - the display will show HOLD
  • stop, reset and exit the program (long press) - the display will go back to standard view for keeping the temperature set by arrow buttons.
The CURRENT LIMIT knob on the annealing controller must be set to a correct value in order to be able to reach the programmed temperature, follow properly the heating ramp but not to burn the heating element.
Ultima modifica il Giovedì, 09 Marzo 2023 10:37