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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.
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There are two modes of operation selectable by the switch:
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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.
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Unit selection (K/°C)
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On the controller press . The double arrow symbol normally next to the set temperature will appear in front of the current unit.
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Using upd/down arrow buttons set the desired unit (C, K or F).
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Confirm with button or discard the change with button.
(You can also select the unit in the e Eurotherm iTools software on the MSB-STATION computer.)
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Short annealing (flash)
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Move the sample to a safe position (not in front of the electron analyzer).
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Check that the CURRENT LIMIT is set to zero (fully counterclockwise).
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Switch the operation mode to SET CURRENT MANUALLY.
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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.
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When you reach the desired temperature decrease the CURRENT LIMIT to zero.
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Long annealing (keeping at temperature)
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Move the sample to a safe position (not in front of the electron analyzer).
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Check that the CURRENT LIMIT is set to zero (fully counterclockwise).
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Switch the operation mode to KEEP TEMPERATURE.
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Use the up/down arrow buttons on the temperature controller to set the desired temperature (shown after on the display, e.g. ).
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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.
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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.
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Start the timer.
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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.
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When the time is over set CURRENT LIMIT to zero (fully counterclockwise).
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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:
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start (double short press) - the display will show RUN
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pause or continue (single short press) - the display will show HOLD
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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.
Last Updated on Thursday, 09 March 2023 10:37